form-3-computer studies summarized NOTES.pdf

1
Computer studies
Form three work

Table of contents
 Data representation in a computer
 Data processing
 Elementary programming principles
 System development

3
Chapter 1
Data representation in a computer

Introduction
 In digital computers,
the user inputs is
converted and
transmitted as
electrical pulses that
can be represented
by two digits ‘1’ and
‘0’ before processing.
These two digits are
referred to as Binary
digits.

Sending data via a telephone line
 When a digital signal is to be
sent over analog telephone
lines e.g. e-mail, it has to be
converted to analog signal.
This is done by connecting a
device called a modem to the
digital computer. This
process of converting a
digital signal to an analog
signal is known as
modulation. On the receiving
end, the incoming analog
signal is converted back to
digital form in a process
known as demodulation.

Concepts of data representation in digital computers
 Data and instructions cannot be entered
and processed directly into computers
using human language. Any type of data
entered must first be converted into
machine-readable form. (Binary form).
Computer together with it’s peripheral
devices handle data in it’s electronic
circuits, magnetic media and in optical
devices.

Data representation in electronic circuits
 Electronic
components such as
microprocessor are
made up of millions of
electronic circuits.
Availability of a high
voltage (ON) in these
circuits is interpreted
as ‘1’ while a low
voltage (OFF) is
interpreted as ‘0’.

Data representation on magnetic media
 The presence of a
magnetic field in one
direction on magnetic
media is interpreted
as ‘1’ while the
absence of magnetic
field is interpreted as
‘0’.

Data representation on optical media
In optical devices, the presence of light is interpreted as ‘1’
while its absence is interpreted as ‘0’.
 BITS – this is a binary digit, which can either be 0 or
1. it’s the basic unit of data or information in digital
computers.
 BYTE – a group of 8 bits. It is the basic unit of
measuring memory size in computers.
 NIBBLE – it is a half a byte or a group of 4 bits.
 WORD – its consists of one or more bytes and is the
largest amount of memory that the computer can
handle.
 WORD LENGTH – is the number of bits in each
word of computer.

Types of data representation
 Number System
 Base conversion
 Negative Numbers
 Binary Addition

Types of number systems
 Decimal Number System
 Binary Number System
 Octal Notion
 Hexadecimal Number System

Decimal Number System
 This number system has ten digits ranging from
0-9. A decimal number should be written with a
subscript 10. e.g. 13210. Each digit of a given
number in the base has a place value, which is
influenced by base ten. E.g. number 123410

Binary Number System
 This number system uses two digits 1 and 0 to
represent numbers. The place value of the digits
of a base two number is influenced by two (the
base/radix). e.g. the place values of the 10102
are illustrated below

Octal Notation
 The octal number system consists of eight digits
running from 0-7. each digit of a number in base
eight has its place value determined by eight.
E.g. 21638 can be expressed as.

Hexadecimal Number System
 This number system consists of sixteen digits ranging
from 0-9 and letters A-F where A is equivalent to 10, B
to 11 up to F which is equivalent to 15, in base ten
systems. Each digit of a number in base sixteen has
its place value expressed in terms of sixteen. For
example, the value 12A3 can be expressed as;

Base conversion
 Decimal to Binary
 Binary to Decimal Number
 Decimal to Octal
 From Octal to Decimal
 Converting Octal to Binary
 From Decimal to Hexadecimal
 Hexadecimal to Decimal
 Hexadecimal to Binary

Decimal to Binary 1
 To convert a number from base 10 to base 2, the
number in base 10 is repeatedly divided by 2 unit the
divided is zero on each division the remainder is noted.
The remainders are copied bottom up wise to give the
binary equivalent of the decimal number.

Decimal to Binary 2
 For fractional numbers
the number is divided into
two parts. The whole
number part and the
fraction part. The whole
number is repeatedly
divided by 2 while the
fraction is repetitively
multiplied by 2 until the
fraction becomes zero or
starts recurring.
(Repeating it self)

Binary to Decimal Number 1
 Steps
1. First write the place
values starting from
the right hand side.
2. Write each digit
under its place value.
3. Multiply each digit by
its corresponding
place value.
4. Sum up the products.

Binary to Decimal Number 2
 For fraction number,
the whole number is
converted to decimal
as above. The
fraction part digits are
divided by multiples of
two starting from the
decimal point.

Decimal to octal 1
 To convert a number
from base 10 to base
8, the number in base
10 is repeatedly
divided by 8, until the
dividend is zero each
division the remainder
is noted.

Decimal to octal 2
 To convert fractional
decimal to octal the
procedure is same as
for fractional decimal
to binary, but the
multiplication is by 8
instead of 2.

Form Octal to Decimal
 The procedure is same
as from binary to decimal,
but the weights as
assigned in terms of 8’s.
 The fractional number are
converted to decimal
using the same
procedure as that of
converting fractional
binary to decimal, but
divisions is by multiplies
of eight.

Converting Octal to Binary
 Each digit is
represented by 3
binary digits. E.g. 7 is
represented as 1112

From Decimal to Hexadecimal 1
 The procedure is
same as from decimal
to binary though
divisions are by 16

From Decimal to Hexadecimal 2
 For the fractional numbers, the fraction part is
multiplied by 16.

Hexadecimal to Decimal
 The same procedure
as from Binary to
Decimal is used with
the weights assigned in
terms of 16’s.
 For fractional
hexadecimal values.
The division is by 16
and the procedure is
the same as the binary
fraction to decimal.

Examples of hexadecimal to binary

Negative numbers
 Both positive and negative numbers can
be represented in the computer memory
during processing. various methods are
used to represent negative numbers in
the computer. These methods are:
i. One’s compliment
ii. Two’s compliment
The negative numbers are used to carry
out subtraction in the computer
arithmetic operations.

One’s complement (1c method)
 In this method the binary bits representing the
negative number are negated that is the 1’s in
the number are changed to 0’s and 0’s to 1’s.

Two’s complement (2c method)
 In this method, the negative number is
represented into binary, then complimented as
in 1c method but a ‘1’ is added to the least
significant digit of the complement value.

Signed magnitude
 In decimal numbers, signed number has a prefix
“+” for a positive number e.g. +3210 and “-” for a
negative number e.g. -3210. in binary, a negative
number may be represented by prefixing a digit
1 to the number while a positive number may be
represented by prefixing a digit 0.
i.e. 1710 ⇒ 100012 (unsigned)
-1710 ⇒ To indicate it’s a negative number we
add an extra bit (1) 100012
+1710 ⇒ To indicate it’s positive we add an extra
bit (0) 100012

Advantages of two’s compliment
 There are no two ways of representing a
zero as in one’s compliment and signed
magnitude.
 Effective addition and subtraction can be
done even with numbers that are
represented with a sign bit.

Binary arithmetics
 Binary addition
 Binary subtraction
 Binary multiplication

Binary addition
 Binary addition rules
A+B sum+ carry
0+0 0 0
0+1 1 0
1+0 1 0
1+1 0 1
1+1+1 1 1

Binary subtraction
 Binary subtraction
rule
A-B difference borrow
0-0 0 0
0-1 1 1
1-0 1 1
1-1 0 0

Subtraction using ones complements

Subtraction using two’s compliment

Binary multiplication
Multiplication rule Product
A * B 0
0 * 0 0
0 * 1 0
1 * 1 1

Examples of binary multiplication

Symbolic representation using coding system
 Binary Coded Decimal (BCD)
 Extended BCD code / standard BCD code
 Extended Binary Coded Decimal
Interchange Code (EBCDIC)
 American Standard Code for Information
Interchange (ASCII)

Binary Coded Decimal (BCD)
 BCD is a 4 bit code used to represent
numeric data only. For example, a number
like 3 can be represented using binary
coded decimal as 00112. BCD is mostly
used in simple electronics devices like
calculators etc.

Extended BCD code / standard BCD code
 This standard binary coded decimal is an
enhanced format of binary coded decimal
(BDC) it’s a 7-bit representation scheme
which can represent non numeric
characters. This allows 64 characters to
be represented. For example letter A is
represented as 1100012 using standard
BCD code.

Extended Binary Coded Decimal Interchange Code (EBCDIC)
 EBCDIC is an 8-bit character coding
scheme used primarily in IBM computers.
A total of 256 (28) characters can be
coded using this scheme. For example
letter A is represented as 110000012 in
EBCDIC code.

American Standard Code for Information Interchange (ASCII)
 ASCII is a 7-bit code, which means that
only 128 characters can be represented.
There is an 8th bit to this coding scheme
which can provide for 256 characters. The
8th bit coding scheme is referred to as an
9-bit ASCII for example letter A is
represented as
10000012 in ASCII code

Review questions 1
1. Differentiate between analog and digital data.
2. Define the following terms:
a. Amplitude
b. Frequency
c. Periodic time
3. Explain the role of a modem in communication.
4. State the reasons for use of binary in digital technology.
5. Using illustration, explain how data is represented:
a. In electronic circuits
b. On magnetic media
c. On CD-ROM
6. Distinguish between:
a. A byte and a nibble
b. Word and word length

Answer of review questions 1-1
1. Analog data is a type of data that is continuous in nature
while digital data is in discrete form.
2. a). Amplitude is the maximum.
b). Frequency is the number of cycles per second.
c). Periodic time is the time taken by a signal to complete
a cycle.
3. A modem converts (modulates) data to be transmitted
over the telephone line from digital signal to analog form.
At the receiving end, the modem attached to the
receiving computer converts (demodulates) the analog
signal to original digital form.
4. Devices designed using binary logic are simple, more
reliable and consume less energy.

5. a). In electronic circuits – availability of high voltage ‘on’ is
interpreted as a ‘1’ while low voltage ‘off’ is interpreted as a
‘0’.
b). On magnetic media, arrangement of magnetic dipoles of
iron oxide in one direction is interpreted as ‘1s” while those
that face in the opposite direction are interpreted as ‘0s’.
c). On the shiny surface of the CD are pits and lands. When a
laser beam falls on the shinny surface, it is reflected and
interpreted as a ‘1’. On the other hand, when the laser beam
takes on the pit or bump, there is no reflection and this is
interpreted as a ‘0’ bit.
6. a). A byte is made up of seven or eight bits while a nibble is
made up of four bits i.e. it is half of a byte.
b). A word consists of two or more bytes while a word length
is used as a measure of the number of bits in each word.

Review questions 2
 Convert the following base two numbers
into denary (base 10) numbers.
a. 01012
b. 11112
c. 101011011102
d. 101111112
e. 10110112
f. 1110001112

Answer of review questions 2
a. 510
b. 1510
c. 139010
d. 19110
e. 8910
f. 45510

Review questions 3
 Using the place value and log division
methods convert each of the following
base 10 numbers to their binary
equivalents.
a. 1010
b. 4310
c. 36510
d. 51210
e. 143
f. 95410

a. 10102
b. 1010112
c. 1011011012
d. 10000000002
e. 100011112
f. 11101110102

Review questions 4
1. Convert the
following binary
numbers to their
decimal equivalents.
a. 0.100112
b. 0.00102
c. 0.101012
d. 11.01102
e. 101.111102
f. 100.1102
2. Convert the
following decimal
numbers into their
binary equivalents.
a. 0.63510
b. 0.45010
c. 2.50010
d. 5.162510
e. 7.187510
f. 0.35010

1. Convert the binary
numbers to their
decimal equivalents.
a. 0.5937510
b. 0.12510
c. 0.6562510
d. 3.37510
e. 5.937510
f. 4.7510
2. Convert the decimal
numbers into their
binary equivalents.
a. 0.1012
b. 0.011102
c. 10.10002
d. 101.001010011
e. 111.00112
f. 110101.01011102

Review questions 5
 Convert the following octal numbers to decimal
numbers.
a. 778
b. 648
c. 1028
d. 12008
e. 10008
f. 1738
g. 1238
h. 7778
i. 3458
j. 1668
k. 3458

a. 6310
b. 5210
c. 6610
d. 64010
e. 51210
f. 12310
g. 8310
h. 51110
i. 22910
j. 11810

Review questions 6
 Convert the following octal numbers to their
binary equivalents.
a. 2448
b. 2478
c. 1628
d. 5658
e. 2228
f. 33708
g. 14138
h. 13318
i. 63478
j. 466538

a. 101001002
b. 101001112
c. 11100102
d. 1011101012
e. 100100102
f. 110111110002
g. 110000110112
h. 10110110012
i. 1100111001112
j. 1001101101010112

Review questions 7
 Convert the following hexadecimal numbers
into decimal numbers.
a. 3216
b. CCD16
c. EFE16
d. 11916
e. 32816
f. ABD16
g. 10AFFD16
h. DDFF3416
i. 11ABDF16
j. CDFF3116

a. 5010
b. 327710
c. 383810
d. 28110
e. 80810
f. 95410
g. 109362910
h. 1454878810
i. 115811110
j. 1350020910

Review questions 8
 Convert the following hexadecimal numbers into binary
form
a. 29416
b. 24716
c. EFD16
d. 90716
e. BAD16
f. CBDF16
g. 585C16
h. ABCD16
i. 55C3A16
j. 33111CF16
k. Convert 1111000110111 to its hexadecimal equivalent.

a. 10100101002
b. 10010001112
c. 11101111111012
d. 1001000001112
e. 1011101011012
f. 11001011110111112
g. 1011000010111002
h. 10101011110011012
i. 1010101110000111
0102
j. 1100110001000100
01110011112
k. IE3716

1. 100012
2. 101102
3. 110012
4. 1100112
5. 10110012
6. 101012
7. 10001112
8. 1111112
9. 10000002
10. 110010112
11. 10010112
12. 11110012

1. 11112
2. 0012
3. 101002
4. 10012
5. 1101012
1. 111112
2. 102
3. 10100102
4. 110001102
5. 100012

Review questions 11
1. Convert the decimal number -7 to 8-bit binary using
ones and twos complement.
2. Using 8-bits length, find the twos complement of the
following decimal numbers.
A) -3110
B) -2810
C) -510
3. Using ones and twos complement perform the following
arithmetic operations.
A) 1410 – 710
B) 2810 – 1210
C) 3410 – 3310
D) 10010 – 5010
E) 10210 – 6410

Answer the review questions 11
1. 111110012
2. A). 111000012
B). 111001002
C). 111110112
3. A). 1112
B). 100002
C). 12
D). 1100102
E). 01001122

Revision questions 1
1. Explain the two types of
data signals.
2. Differentiate between
A) Octal and decimal
number systems.
B) Binary and hexadecimal
number systems.
3. Convert the following binary
numbers to their decimal
equivalents.
1. 1011102
2. 1010112
3. 01102
4. 101012
4. Convert the following
decimal numbers to their
decimal binary
equivalents.
A) 78910
B) 57010
C) 4210
D) 3010
5. Find the sum of the
following binary numbers.
A) 11102 + 11112 =
B) 0012 + 1002 =
C) 11012 + 10112 + 1002 =
D) 10102 + 1012 =
E) 1112 + 112 =

Answer of revision questions 1
1. Analog and digital
2. A). Octal number system is a base 8 system while the
decimal number system is a base 10 system.
B). Binary number system is a base 2 system while
hexadecimal number system is a base 16 system.
3. A). 4610
B). 4310
C). 610
D). 2210
4. A). 11000101012
B). 10001110102
C). 1010102
D). 111102

1. Work out the following binary
subtraction using direct, ones
and twos complement
methods.
A) 11001 – 1101
B) 1000 – 101
C) 100011 – 111
D) 10101110 – 1000110
E) 10001000110 – 101
2. Find the ones and twos
complement of the following
decimal number in binary form.
A) -7510
B) -8010
C) -10010
3. Determine the value of X in the
equations:
A) 1001102 – X2 = 0010102
B) X2 + 11012 = 7010
4. Work out the decimal equivalents
of the following binary numbers.
A) 0.100102
B) 101.112
C) 11.1012
D) 0.0012
5. Work out the decimal equivalents
of the following binary numbers.
A) 0.3510
B) 2.5010
C) 0.2010
D) 7.12510

1. A). 101012
B). 1012
C). 111002
D). 11112
E). 10102
2. A). 11002
B). 0112
C). 111002
D). 11010002
E). 100010000012
3. A). 111002
B). 1110012
1. A). 0.562510
B). 5.7510
C). 3.62510
D). 0.12510
2. A). 0.0101102
B). 10.12
C). 0.00112
D). 111.0012

1. Write down the character represented by the following
codes:
A) ASCII
i. 0110000
ii. 0110111
iii. 1000011
iv. 1011001
B) EBCDIC
1. 11110000
2. 11110111
3. 11000001
4. 01011101

ASCII Char
acter
EBCDIC Char
acter
A). 0110000 0 11110000 0
B). 0110111 7 11110111 7
C). 1000011 C 11000001 A
D). 1011001 Y 01011101 )
Num
ber
1’s
complement
2s
complement
A) -75 0110100 0110101
B) -80 0101111 0110000
C) -100 0011011 0011100

Definition of Terms
 Data – this is a collection of raw facts (figures, letters,
characters etc) that convey little meaning by
themselves.
 Information – this refers to data that has undergone
processing and is meaningful to the user when he/she
need it, in the form he needs and at the time he/she
need it.
 Data processing – refers to the process of
transforming raw facts into meaningful output
(information)
 Data processing cycle – refers to input process output
stages that data goes through to be transformed into
information.

Data processing cycle
Data collection
Data input
Output
Processing

Stages of data processing cycle
1. Data collection – this involves looking for or getting
the data from its point of origin for processing
purpose.
2. Data input – this is the process where the collected
data is converted from human readable form to
machine – readable form.
3. Processing – this is transformation of input data by
the central processing unit to a more meaningful
output.
4. Output – this is the final activity of data processing
cycle which produces the desired output
(information). The information is then distributed to
the target groups.

 Interview
 Questionnaire
 Observation
 Record inspection
Methods of data collection

Stages of data collection
 Depending on the method of data
collection used, the process of data
collection may involve the following stages.
Data creation
Data transmission
Data preparation
Media conversion
Input validation
Sorting

Data creation
 This is the process of putting together
facts in an organised format. This may be
in form of manually prepared documents
or captured from the source using data
capture devices. E.g. scanners, digital
camera etc.

Data transmission
 This refers to the transfer of data from the
point of collection (source) of the point
where processing is to be done.
Transmission can be electronically through
computer – to – computer, physically by
the post office etc.

Data preparation
 This refers to conversion of data from
source document to machine – readable
form. Data collected using devices that
capture data in digital form do not require
transcription conversion.

Media conversion
 Data may need to be converted from one
medium to another. E.g. from a compact
disk to hard disk for faster input.

Input validation
 Data entered into the computer is
subjected to validity and verification
checks before processing.
Verification – this involves checking that what
is on input document is exactly the same as
what is entered into the computer.
Validation – this is identification and removal
of errors by the computer through the control
of the program.

Sorting
 The source documents are arranged in a
particular order for easy and faster entry.

Description of errors in data processing
 The accuracy of the data entered in the
computer determines the accuracy of the
information given out.

Types of data processing errors
 Transcription errors – these errors occurs during
data entry. These errors includes misreading
errors and transposition errors.
 Computational errors – they occur when an
arithmetic operation does not produce the
expected results. They include overflow errors,
truncation errors and rounding errors.
 Algorithm or logical errors – these errors occurs
as a result of wrong algorithm design.

Misreading errors
 They are brought about by incorrect
reading of source document by the user
and hence entering wrong values. This
may be caused by bad hand writing or
confusion on source document. E.g. the
number ‘5’ can be typed as s or letter 0
typed as Zero.

Transposition errors
 These errors occurs as a result of
incorrect arrangement of characters. i.e.
putting characters in the wrong order. E.g.
the user may enter 542 instead of 542.
transcription errors can be eliminated by
use of data capture devices.

Overflow errors
 This errors occurs if the result from a
calculation is too large to be stored in the
allocated memory space. E.g. if the
memory space can accommodate an 8-bit
number and the results from arithmetic is
9-bit number.

Truncation errors
 This result from having real numbers that
have a long fractional part which cannot fit
in the allocated memory space. The
computer cut off the extra characters from
the fraction part. E.g. a number like
0.854692 can be truncated to four digits as
0.854.

Rounding errors
 This results from a raising or lowering a
digit in a real number to the required
rounded number. E.g. a number 3.59 can
be rounded to 3.6.

Data integrity
 Data integrity refers to the accuracy and
completeness of data entered in a
computer or received from the information
system.

Factors that determine data integrity
 Accuracy
 Timeliness
 Relevance
 Audibility

Accuracy
 This refers to whether information/data is
accurate – true or untrue. As long as the
correct instructions and data are entered,
computers produce accurate results
efficiently.

Timeliness
 This refers to whether the information is
available when it is needed, and if its
outdated when it is received or when it is
used. If information is not available when
needed or its outdated by the time its used
then has little or no value in decision
making.

Relevance
 The data entered must be pertinent to the
proce3ssing needs at hand and must meet
the requirements of the processing cycle.

Audibility
 Audit ability also refers to as verifiability.
This is the ability of users to check the
accuracy and completeness of information.

Threats to data integrity
 Threats to data integrity can be minimised
through the following;
Using error detection and correction software when
transmitting data.
Design user interfaces that minimizes chances of
invalid data entry.
Using devices that capture data directly from source
e.g. scanners etc.
Control access to data by enforcing security
measures.
Back up data preferably on external storage media.

Data processing methods
 Data can be processed using one of the
following methods.
Mechanically
Manually
Electronically

Manual data processing
 In this method staff in an
organisation uses the laid
down procedures and rules
to collect data, process and
distribute information to
relevant departments for
use. The tasks are done
manually with a pen and a
paper. No machines are
used to process data
instead they use simple
tools like tables and rulers.

Mechanical data processing
 Mechanical systems
are those where staff
use various
mechanical machines
like calculators,
typewriters, cash
registers duplicating
machines etc to
perform operations.

Electronic data processing
 In this system, data is
manipulated using electronic
machines to produce
information. This method is
faster and more accurate than
the manual and mechanical
where large volumes of data
are to be processed. This
method involves the use of
computers and other
electronic machine like mobile
phones, washing machines,
modern digital TVs etc.

Factors determining the methods of data processing
 Size and type of business
 Timing aspects
 Link between application

Computer files
 A file is a collection of related records that
give a complete set of information about a
certain item or entity. A file can be stored
manually in a file cabinet or electronically
in a computer storage device.

Advantages of computerized filling system
 Information takes up less space than the
manual system.
 Enhance data integrity and reduces
duplication.
 Offers faster access and retrieval of data.
 It’s much easier to update or modify
information.

Elements of a computer file
 A computer file is made up 3 elements.
 Characters – this is the smallest element in a
computer file and refer to a letter, number, symbol
that can be entered, stored and output by a computer.
 Field – a field is a single character or a collection of
characters that represents a single piece of data. For
example in employees record, the name of employee
is a field.
 Records – is a collection of related fields that
represents a single entity. For example in employees
record, details of each employee in a row. E.g. Name,
IDNO, sex, Department etc make up a record.
Computer files can be viewed in two ways.

Logical file
 This is the way the user views the file in
terms of its contents and the processing to
be carried upon them.

Physical file
 This is the actual arrangement of the file
contents into the storage media surface
and how the processing operations are
made possible.

Types of computer processing files
 Master file
 Transaction file (movement file)
 Reference file
 Sort file
 Back – up file
 Report file

Master file
 This is the main file that contains
permanent records about a particular item
or entries. The master file contains both
static and dynamic fields. For example a
payroll system might keep a master file
containing employees personal details
(name, address, date of birth, sex etc)
which rarely change (static fields) and data
describing the earnings and deductions
which frequently change (dynamic fields).

Transaction file (movement file)
 This file includes input and output files for
holding temporary incoming or outgoing
data. It contains data about an
organisation activities taking place for
some period of time. This file is used to
update dynamic data on master files.

Reference file
 They are permanent or semi permanent
and are used for reference or look up
purposes. They contain records that are
fairly static. E.g. price, lists, Pay As You
Earn etc.

Sort file
 These files are created from existing
transaction or master files. They are used
where data is to be processed
sequentially. Data or records are first
sorted in a particular format for example
they are arranged in ascending or
descending order of the key field and
stored in the sort file.

Back – up file
 These files are duplicate copies of existing
files. They are used to supplement the
operational files in case of loss by any
reason. They are created any time and
update is carried out on the master file.

Report file
 They contain sets of records extracted
from data in the master files. They are
used to prepare reports that can be printed
at a later date, for example, list of
absentees, overtime etc.

File processing activities 1
 Updating – refers to changing data in
master file to reflect the current status.
 Referencing – happens when it is made to
particular records to ascertain what is
contained therein. The activity does not
alter the contents of master file from a file.
 Sorting – this entails arranging of file
contents into some pre – determined
sequence of the key field, which occupy
the same position on the records.

File processing activities 2
 Merging – the process that combines the
contents of two or more input files into one
output files.
 Matching – the input files records are
matched/compared to ensure that records exist
in both the files.
 Summarizing – the records of interest from the
file are accumulated to form a record in the
output file.
 Searching – it entails looking for the record of
interests from the file.

File updating 1
 Hit rate – hit rate is used to describe the
rate of processing of a master file in terms
of its active records. For example, if 600
transactions are processed each day
against a master file of 12,000 records,
then the hit rate is said to be 5% i.e.
600/12000*100

File updating 2
 Volatility – this is the frequency with which
records are added to the file or deleted
from it. If the frequency is high, then the
file is said to be ‘volatile’ otherwise ‘static’.
 Size – refers to the amount of data stored
in the file. Its expressed in terms of the
total number of records in the file.
 Growth – files will always grow as new
records are added to it.

File organisation methods
 File organisation is the arrangements of
records within a particular file. There are
four methods of storing files and retrieving
them from secondary storage devices.

Sequential file organisation
 In this organisation records are stored and
accessed in a particular order sorted using
key field. The key field is used to search
for a particular record. Searching
commences at the beginning of the file
and proceeds to the ‘tail’ of the file until the
record is reached. Mainly used with
magnetic tapes.

Advantages of sequential file
 Simple to understand the approach.
 Easy to organise, maintain and
understand.
 Reading a record requires only the key
field.
 Inexpensive input/output media and
devices are used.

Disadvantages of sequential file
 Entire file must be accessed even when
the activity rate is very low.
 Random enquires are impossible to
handle.
 Data redundancy is typically high.

Random or direct file organisation
 In this organisation records are stored
randomly but accessed directly. To access
a file stored randomly, a record key is
used to determine where a record is
stored on the storage media. Used in
magnetic and optical disks.

Advantages of random or direct file
 Records are quickly accessed.
 File update is easily achieved.
 They do not require the use of indexes.

Disadvantages of random or direct file
 Data may be accidentally erased or over
written. Unless special precaution taken.
 Expensive hardware and software
resources are required.
 Relative complexity of programming.
 System design around it is complex and
costly.

Serial file organisation
 The records are laid out
contiguously one after the
other in no particular
sequence. The records
are stored one after the
other in the same order
they come into the file
and there exists no
relationship between
contiguous records. Used
with magnetic tapes.

Indexed sequential file organisation
 This method is similar to sequential
method, only that an index is used to
enable the computer to locate individual
records on the storage media. Used with
magnetic disk.

Advantages of indexed sequential file
 Records can be accessed sequentially or
randomly.
 Records are not duplicated.
 Accessing of records can be fast if done
randomly.

Disadvantages indexed sequential file
 Storage medium is rather expensive.
 Accessing records sequentially is time
consuming.
 Processing records sequentially may
introduce redundancy.

Electronic data processing modes
 On-line processing
 Time sharing processing
 Real time processing
 Multi-programming / multi-tasking
 Distributed processing
 Batch processing
 Multi-processing
 Interactive processing

On-line processing
 In this processing the result of data
processing is available immediately. All
the computer peripherals and equipments
are under the direct control of the central
processor. As soon as the input
transactions are available, they are
processed to produce the required
information. The user can interact with the
system at any time of processing using
input/output facilities.

Application of on-line processing
 Banking
 Stock exchange
 Stock control
 Water/electricity billing

Advantages of on-line processing
 Files are maintained up to date.
 Information is readily available for current
decisions.
 File enquiries possible through the
terminals (work station)

Disadvantages of on-line processing
 System are complex to develop.
 Are costly in terms of hardware, software,
storage media etc.

Time sharing processing
 In this mode the central processor serves two or more users
with different processing requirements (tasks). The central
computer is available to a variety of uses, connected to the
central computer via communication links who may wish to
process their data and receive information. The processor time
is divided out appropriately among the user task is into time
slices. Control is switched from one job to another, under the
influence of the operating system. The time slice is equal for all
jobs and it’s assigned to jobs waiting in a queue. In one turn,
only one slice is allocated to the job. The jobs in the queue are
assigned the time slice from the head of the queue towards the
tail. Jobs that require more time slices are chained to the tail
queue. New jobs into the queue are added at the tail of the
queue. The wholly processed jobs output results. The
incomplete jobs go back to the tail of the queue to await their
next turn.

Application of time sharing processing
 Bureau
 Learning institutions.
 Companies.

Advantages of time sharing processing
 Better services to the users, for the
information/output is fast.
 Files enquiries is possible since files are
held on-line.
 User interaction is possible through
terminals.

Disadvantages of time sharing processing
 User has no control over the central
computer.
 Not reliable with regard to data security.
 Response time is slow where there are
many tasks.

Real time processing
 In this mode, computer processes the
incoming data as soon as it occurs,
updates the transactions file and gives an
immediate response that would affect the
events as they happen. The main purpose
of a real time processing is to provide
accurate, up to date information hence
better services based on a real situation.

Application of real time processing
 Air reservation
 Hotel reservation
 Chemical plant processing

Advantages of real time processing
 Information is readily available for instant
decision.
 Provides immediate control / information.
 Its fast and reliable.

Disadvantages of real time processing
 Requires complex and expensive
operating system.
 They are not easy to develop.
 Require Front End Processors (FEPS) to
relieve the ventral processor.

Multi-programming / multi-tasking
 In this processing more than one program
are executed apparently at the same time
by a single central processing unit. The
operating system allocated each program
a time slice and decides what order they
will be executed.

Advantages of multi-programming / multi-tasking
 Increases the productivity of the computer
by reducing CPU idle time.
 Reduces the incidence of peripheral
bound operations.

Disadvantages of multi-programming / multi-tasking
 Requires more expensive CPUs.
 Operating system is complex and more
difficult to operate.

Distributed processing
 This processing refers to dividing
(distributing) processing tasks to two or
more computers that are located on
physically separate sites but connected by
data transmission media. For example, a
distributed database will have different
tables of the same database residing on
separate computers and processed there
as need arises.

Application of distributed processing
 Banks where customers can be served
from different branches but information is
updated at the head branch.

Advantages of distributed processing
 Less risk to system breakdown.
 In case of data loss, only a small portion of
the data is lost.
 Reduction of the load on the host.
computer hence faster processing.

Disadvantages of distributed processing
 Expensive due to extra communication
costs.
 More sophisticated software required to
maintain data integrity.

Batch processing
 This is processing mode where the
transactions are accumulated over a
period of time and then proce3ssed at a
pre-specified time to produce a batch of
output. The data to be processed e.g. daily,
weekly, monthly etc then processed at
once.

Application of batch processing
 Payroll processing.

Advantages of batch processing
 Simple to develop.
 Timing reports is not a necessity.
 The unit cost of processing is low.

Disadvantages of batch processing
 Time lag between origination of the
transactions and the information
availability.
 Late information is not suitable in
situations where instant decisions are
requires.
 Its difficult to provide the desired priority
scheduling.

Multi-processing
 This refers to the processing of more one
task at the same time on different
processors of the same computer. In such
systems, a computer may contain more
than one independent central processing
unit which works together in a coordinated
way. At a given time the processor may
execute instructions from two or more
different programs or from different parts
of one program simultaneously.

Interactive processing
 In this processing, there is continuous
dialogue between the user and the
computers. As the program executes, it
keeps on prompting the user to provide
input or respond to prompts displayed on
the screen.

Factor to consider in selecting the data processing mode
 The need for direct information retrieval
and/or file interrogation.
 The control over the resources e.g. files,
input/output devices.
 The cost of acquiring the relevant
hardware, software, media etc.
 The optimization of the processing time.
 The time factor of the information for
decision making by mangers.

Review questions 1
1. Define the following terms:
A) Data processing.
B) Data processing style.
2. Using an illustration, describe the four primary stages of the
data processing cycle.
3. Outline the stages of data collection.
4. You may have come across the term Garbage In Garbage Out
(GIGO). What is its relevance to errors in data processing.
5. Explain the two types of transcription errors.
6. State three types of computational errors.
7. Define the term data integrity.
8. Give three factors that determine the integrity of data.
9. State at least five ways of minimising threats to data integrity.

1. A). Data processing refers to the transformation of raw
data into meaningful output (information).
B). Data processing cycle are the stages that data goes
through during its transformation into information. The
output may be used later as input to another processing
task.
2. Data collection → data input → data processing →
output.
3. A). Data creation.
B). Data transmission.
C). Data preparation.
D). Media conversion.
E). Input validation.
F). Sorting.

4. The accuracy of data entry determines the accuracy of
the output.
5. A). Wrong entry due to misreading the source data e.g.
entering C instead of G (transcription error).
B). Transposition – interchanging values e.g. 396
instead of 369.
6. Overflow and underflow.
Truncation.
Rounding.
7. A). Data integrity refers to accuracy and completeness
of data.
B). Accuracy, timeliness and relevance.
C). Banking up, enforcing security, using input devices
that capture data directly from the source etc.

Revision questions
1. Distinguish between data and information.
2. Describe types of data processing methods.
3. State at least four advantages of storing data in
computer files over the manual filing system.
4. State elements that make up a computer file.
5. Differentiate between a logical file and physical file.
6. Explain at least six types of computer files.
7. Distinguish between
A) Sequential and serial file organisation methods.
B) Random and indexed-sequential file organisation methods.
8. Describe at least five types of electronic data
processing modes.

1. Data refers to raw facts that do
not have much meaning while
information refers to the
meaningful output after
processing.
2. Data processing methods:
manual, mechanical and
electronic.
3. A). Takes up less space.
B). Easier to update or modify.
C). Faster access and retrieval.
D). Enhances integrity.
4. A). Characters.
B). Field.
C). Record.
5. A logical file is viewed in terms
of what data items and
processing operation may be
performed on the data while a
physical file is viewed in terms
how data is stored and how it
is to be processed.
6. A). Master file.
B). Transaction file.
C). Reference file.
D). Backup file.
E). Report file.
F). Sort file.

1. In sequential file organisation, records are stored in a sorted order using a
key field while in serial file organisation, records are not sorted in any way.
2. In random file organisation, records are stored randomly but accessed
directly. On the other hand, in indexed-sequential, records are stored
sequentially but accessed directly using an index.
3. On-line distributed – the data being processed is accessed, processed
and updated in real time.
4. Time-sharing-competing computers are allocated time slots to use
computer resources.
5. Batch processing – all the available jobs are processed in bulk all at once.
6. Interactive processing – the computer presents the user with input
screens / the user inputs data as processing continues.
7. Real time – data being processed is updated online and the results
thereof affect current processing logic.
8. Multi-tasking – several computer programs / tasks run concurrently at the
same time sharing resources in shifts.
9. Multiprocessing – several programs / tasks run concurrently on different
processors.

168
Chapter 3
Elementary programming principles

Introduction
 Human beings have evolved
from the stone age to a highly
sophisticated and advanced
society by inventing things like
the wheel, fire, transistors and
today’s ultra modern devices
like computers. The idea of
computers started way back in
the nineteenth century. The first
generation computers called
Electronic Numeric Integrator
And Calculator (ENIAC 1) were
operated by plugging wires into
a control panel that resembles
the old telephone switchboards.

Computer programming
 A program – is an organised list of statements
(instructions) that when executed, causes the
computer to behave in a predetermined manner
or carry out a defined task.
 Programming – refers to the process of
developing computer (instructions) programs
used to solve a particular task.
 A computer program – is designed using a
particular programming language. Each
language has a special sequence or order of
writing characters usually referred to as syntax.

Terms used in programming
 Source program
 Object code
 Translator
 Assembler
 Interpreter
 Compiler

Source program
 This refers to the program code that the
programmer enters in the program editor
window that is not yet translated into
machine-readable form.

Object code
 This refers to the program code that is in
machine-readable. i.e. a source code that
has been translated into machine
language.

Translator
 These are programs that
translates/convert the source program into
object code. E.g. assemblers, compliers,
interpreters etc.

Assembler
 An assembler translates a program written
in assembly language into machine
language,

Interpreter
 This translates the source program line-
by-line, allowing the CPU to execute one
line before translating the next. The
translated line is not stored in the
computer memory, hence every time the
program is executed, it has to be
translated.

Complier
 This translates the entire source program
into object code. The compiler translates
each high-level instruction into several
machine code instructions in a process
called COMPILATION and produces a
complete independent program that can
be run by the computer as often as
required without the original source
program being present.

Difference between the interpreters and compilers
Interpreters Compilers
Translates the source program
one statement at a time.
Translates the entire source
code at once before execution.
Translates the program each
time it is run hence slower than
compiling.
Compiled program (object
code) can be saved on a
storage media and run as
required, hence executes
faster than interpreted
programs.
Interpreted object code takes
less memory compared to
compiled program.
Compiled programs require
more memory as the object file
are larger.

Level of programming languages
 There are 2 major levels namely;
Low-level languages.
High-level languages.

Low-level languages
 These languages are classified as low
because they can be easily understood by
the computer directly or they require little
effort to translate into computer
understandable form. These languages
are hardware oriented and therefore they
are not portable. i.e. a program written for
one computer cannot be installed and
used on another.

High-level languages
 These languages are very close to the
human language (English-like) and they
can be read and understood even by
people who are not experts in
programming. These languages are
machine independent. This means that a
programmer concentrates on problem
solving during a programming session
rather than how a machine operates.

Types of low level languages
 Machine language (First generation
languages).
 Assembly languages (Second generation
languages)

Machine language
(First generation languages)
 In this language, instructions are written using binary
logic. Given that data and instructions are in binary
form, many lines of codes are needed to accomplish
even a simple task like adding two numbers i.e. a
program written in this language look like this.
11100110 00000011 19999991
00001111 10001101
10001111 11111111 10000011
The program code is hard for human to understand
but it’s easily understood by computers.

Assembly languages
(Second generation languages)
 This language is close to the machines vocabulary
rather than human beings vocabulary. It was
developed in order to overcome the difficulties of
understanding and using machine language. This
language helps the programmers to write programs as
a set of symbolic operation codes called Mnemonics.
Mnemonics are basically shortened two or three letter
words. A sample program written in Assembly
language.
MOV AX, 15 (move 15 to register Ax)
SUB AX, 10 (Subtract 10 from the value Ax)
Programs written in this language require an
assembler to convert them into machine language.

Classes of high level languages
 Third generation languages (3GLS)
 Forth generation languages (5GLs)
 Fifth generation languages (5GL’s)
 Object Oriented Programming Language
(OOP)
 Web scripting languages

Third generation languages (3GLS)
 This generation languages is also called
structured or procedural languages. A
procedural language makes it possible to
break a program into components called
modules. Each performing a particular
task. Structured programming has
advantages because its flexible, easier to
read and modify.

Examples of third generation programming language
 Pascal – was developed to help in the teaching and learning of
structured programming.
 Fotran – was developed for mathematics, scientists of
programs with mathematical expressions.
 Cobol – was designed for developing programs that solve
business problems.
 Basic – developed to enable students to easily learn
programming.
 C – used for developing system software e.g. the operation
systems. Its very powerful high level language because of its
ability to provide programmer with powerful aspects/features of
low level.
 Ada – this language is suitable for developing military, industrial
and real – time systems.

Forth generation languages (4GLs)
 This generation make programming an even
easier task than the third generation language
because they present the programmer with more
programming tools. Examples of such tools are
command buttons, forms etc. the 4 GLs are easy
to learn and understand because they are user
based. The languages syntax (grammar) is
natural, near English language and use menus
to prompts to guide a non-specialist or retrieve
data with ease.

Examples of 4GLs
 Visual Basic
 Delphi Pascal
 Visual Cobol
 C++

Fifth generation languages (5GL’s)
 These languages are designed around the
concept of solving problems by enabling
the computer to depict human like
intelligence. These programs are designed
to make the computer solve the problem
for the programmer rather than
programmer spending a lot of time to
come up with the solution.

Examples of 5GL’s
 PROLOG
 MERCURY
 LISP
 OCCAM

Object Oriented Programming Language (OOP)
 The concept behind OOP languages is to look at
a program as having various objects interacting
to make up a whole. Each object has a specific
data values that are unique to it (called state)
and a set of the things it can accomplish called
(functions or behaviour). This process of having
data and functions that operate on the data
within an object is called Encapsulation.
Several objects can then be linked together to
form a complete program. OOP has greatly
contributed to development of Graphical user
interface operation system and application
programs.

Examples of OOP
 Java
 Simula
 Small talk

Web scripting languages
 These languages are used to develop or add functionalities on
web pages. Web pages are hypertext documents created in a
language called HyperText Markup Language (HTML). The
languages consist of markup tags that tell the Internet browser
that the file contains HTML-code information and is
distinguished by a file extension of HTML. The markup tags
define the various components of a World Wide Web document
such as heading, tables, paragraphs, lists etc. HTML does not
have the declaration part and control structures, hence it’s not
considered as a true programming language. Due to its
simplicity, it has many limitations and cannot be used alone
when developing functional websites. Some special blocks of
codes called Scripts may be inserted in HTML pages using
scripting languages like JavaScript, VBScript etc in order to add
functionality to HTML pages.

Examples of HTML tags and their meanings
Tag Meaning
<HTML>
</HTML>
Marks the beginning and end of a HTML document. All other tags and text fall
between these two tags.
<HEAD></HEAD> Marks the header part of the document.
<TITLE>
</TITLE>
Gives title of te web page. Text between this tags appears in the title bar when the
page is browsed.
<BODY></BODY> Marks the body part of the document.
<CENTER></CENTER
>
Centres text and objects on the web page.
<B></B> Bolds the text on the web page.
<I></I> Italicise the text.
<H1>
</H1>
Sets size of text on the web page with H6 displaying the smallest and H1 the
largest size.

Creating a script using Javascript 1
 Javascript is a popular scripting language.
Before writing your HTML program with a
script inserted, make sure that you have
the latest browser software installed on
your computer. Older browsers may not
have support for Javascript. If you are
using Internet Explorer, it should be
version 5.0 and above.

 Open Notepad and key in the following program. Do not
write the numbers to the left of each line of code.
1. <HTML>
2. <HEAD>
3. <TITLE>Scripting Example</TITLE>
4. </HEAD>
5. <BODY>
6. <HI><CENTER><B>we are the world</B></CENTER><HI>
7. <SCRIPT>LANGUAGE=‘JavaScript’>
8. document.write(‘My name is strongman’);
9. alert(‘congratulations for succeeding to run this script’);
10. </SCRIPT>
11. </BODY></HTML>

 After typing the entire
program, save your file
on the desktop as
Example.html and then
close the notepad. Notice
that the icon to your file
on the desktop look like
that of the default web
browser in your computer.
 To view the web page,
double click the icon of
the file Example.html on
the desktop. Figure right
shows as open webpage.

Advantages of low-level languages
 The CPU understands machine language
directly without translation.
 They are stable and hardly crash or
breakdown once written.
 Running a program is fast, no compilation
is needed.
 They are economical in terms of the
amount of memory they use.

Disadvantages of low-level languages
 They are difficult and cumbersome to use
and learn.
 Require highly trained experts to both
develop and maintain programs.
 Debugging programs is difficult.
 They are machine dependent.
 The programs are long.

Advantages of high-level languages
 The programs are portable (not machine
dependent).
 They are user friendly and easy to use and
learn.
 They are more flexible.
 They are easy to debug.
 They provide better documentation.
 Require less time to code.

Disadvantages of high-level languages
 Program executed more slowly.
 Require larger CPU storage capacity for
compilation.
 They have to be translated to machine
readable form before

Program development
 There are six stages of program
development. They include:
Problem recognition
Problem definition
Program design
Program coding
Program testing
Program implemetation
Documentation

Problem recognition
 This refers to the understanding and
interpretation of a particular problem. To
understand a problem one has to look for
key words such as compute, evaluate,
compare etc. a programmer identifies
problems in the environment and seeks to
solve them by writing a computer program
that would provide the solution.

Circumstances that can cause the
programmer to identify a problem
 Opportunity to improve the current
program.
 A new directive given by the management
requiring a change in the status quo.
 Problems or undesirable situations that
prevent an individual or organisation from
achieving their purpose.

Problem definition
 At this stage the programmer tries to determine
or define the likely input, processing and
expected output using the keywords outlined at
the problem recognition stage. The boundaries
of the expected program are established and if
several methods to solve the same problem are
identified the best alternatives should be
chosen. At the end of the stage requirement
documentation for the new program is written.

Program design
 This is the actual development of the program’s processing or
problem solving logic called algorithm. (A limited number of
logical steps that a program follows in order to solve a problem).
The programmer comes up with an algorithm after analysing
the requirements specifications. Some of the programs are
made up of one large block code. i.e. they are Monolithic while
others are made of several units called modules which work
together to from the whole program. In modular programming,
each module performs a specific task. This approach makes a
program flexible, easier to read and debug. This phase enable
the programmer to come up with models of the expected
program. The model show the flow of events and data
throughout the entire program from input of a program.

Monolithic and modular program

Program coding
 This is the actual process of converting a
design model into its equivalent program.
This is done by creating the program using
a particular programming language. The
end result of this stage is a source
program that can be translated into
machine readable form for the computer to
execute and solve the target problem.

Program in Pascal and C++
Program in Pascal Program in C++
Program AreaCircle (input, output);
Const Pi = 22/7;
Var
Radius, Area: real;
Begin
WriteIn (‘Enter the radius’);
ReadIn (radius);
Area: = Pi *Radius *Radius;
WriteIn (‘The area is’, Area)
End.
#include<iostream.h>
double radius, area;
double pi = 22/7;
main ()
{
cout<<‘Enter the radius’;
cin>>radius;
area = pi *radius *radius
cout<<‘The area is’, area;
return 0;
}

Explain the program codes 1
Pascal code C++ code Explanation
Program Areacircle
(input, output);
#include<iostream.h> The header of the
programs. The statements
in () and <> shows that
the user inputs data via
the keyboard and the
program display
information on the screen.
Const Pi = 3.142; double pi = 3.142; A constant has been
declared with a name pi
and value 3.142.
Var
Radius, area:real
double area, radius; Real variables with
fractional part have been
declared.

Begin { Marks the beginning of
the program body or
executable statements.
WtiteIn cout<<’Enter radius’: Display on the screen the
string between inverted
commas.
ReadIn (Radius) cin>>radius; Displays a blinking
cursor that tells the user
that an input is needed
before the program can
continue.

Area: = Pi * Radius
* Radius
area = pi * radius
* radius;
Calculates the area. Notice
the assignment statement in
Pascal is : = while in C++ it is
=
WriteIn (‘The area
is’, Area);
cout<<”The area
is’, Area<<”∖n”;
Display the value stored in
the variable Area.
End. return 0;
}
Marks the end of the program

Program Testing and Debugging
 After coding the program has to be tested
and the errors detected and corrected.
Debugging refers to detection and
correction of errors that may exist in the
program. Program testing involves
creating test data designed to produce
predictable output. They are two types of
errors (bugs) that can be encountered
when testing.

Types of errors (bugs)
 Syntax errors – they occur as a result of
improper use of language rules. E.g.
grammar mistakes, punctuation, improper
naming of variables etc. these errors are
detectable by translator and must be
corrected before the program runs.
 Logical errors – they are not detectable by
the translator. The program rules but gives
wrong out put or halts during execution.

Methods of errors detection
 Desk checking / dry – run.
 Using Debugging utilities.
 Using Test Data.
 Implementation and maintenance
Implementation.
 Review and maintenance.
 Program documentation.

Desk checking / dry – run
 It involves going through the program
while still on paper before entering it in the
program editor.

Using Debugging utilities
 In the program editor, you can run the
debugging utilities during translation to
detect syntax errors.

Using Test Data
 The programmer carries out trial runs of
the new program. At each run he enters
various data variations and extremes
including data with errors to test whether
the system will grid to a halt. A good
program should not crash due to incorrect
data entry but should inform the user
about the anomaly.

Implementation and
maintenance implementation
 This is the actual delivery and installation
of the new program ready for use, creating
data files and train people to use the
system. The new system will change the
way things are done hence it should be
reviewed and maintained.

Review and maintenance
 This stage is important because of the
errors that may be encountered after
implementation. A program may fail due to
poor use, hence proper training and post
implementation support of users will
reduce chances of having them entering
invalid data that crash the program.

Program documentation
 This is writing of support materials
explaining how the program can be used
by users, installed by operators or
modified by other programmers. All stages
of program development should be
documented in order to help during future
modification of the program.

Types of documentation
 User oriented documentation – these type enables
the user to learn how to use the program as quickly
as possible and with little help from programmer.
 Operator oriented documentation – meant for
computer operators. E.g. Technician. It helps them
to install and maintain the program.
 Programmer oriented documentation – written for
skilled programmers. It provides necessary
technician information to help in future modification
of program.

Development of algorithms
 Algorithms – refers to a limited number of
logical steps that a program follows in
order to solve a problem.
 Pseudocode – refers to a set of
statements written in a readable language
(English – like) but expressing the
processing logic of a program.

Guidelines for designing a good pseudocode
 The statements must be short, clear and
readable.
 Pseudocode lines should be clearly
outlined and indented clearly.
 It should show clearly the start and stop of
executable statements and control
structures.
 Statements must not have more than one
meaning.

Examples of Pseudo code
Solution
START
Print “Enter two numbers”
Input x,y
Sum – x + y
Average = sum / 2
PRINT sum
PRINT Average
STOP
 Write of Pseudo code
that can be used to
prompt the user to
enter two numbers,
calculate the sum and
average of the two
numbers and then
display the output on
the screen

Program flowcharts
 A flowchart is a diagrammatic
representation of a program in algorithms.
It uses statements and symbols that have
specific meaning. The symbols are of
different standard shapes linked to show
the order of processing. Each shape
contains note stating what the operation is.

Most common program flowcharts
 Ellipse: denotes the beginning and end of the
program algorithm.
 Parallelogram: used to denote an input or output
operation. For example, READ A,B, PRINT SUM
=A+B
 Rectangle: indicates that a processing or data
transformation is taking place. For example SUM
=A+B.
 Rhombus: used to specify a condition. A condition
must evaluate to a boolean value (True or false) for
the program to execute the next instructions.
 Connector: used as a connecting point or interface
for arrows coming from different directions.
 Arrow: used to indicate the direction of flow of the
program logic.

Guidelines for drawing a flowchart
 There should be only one entry and one
exit point of a program algorithm.
 Use correct symbol at each stage in the
flowchart.
 Avoid crossed flow lines.
 Be as neat and tidy in drawing as possible.
 General direction of flow in any flowchart
is from top to bottom, left to right.

Examples of flowchart
Solution  Draw a flowchart for a
program used to
prompt the user to
enter two numbers.
The program should
find the sum, and
average then display
the output.
Sum = X + Y
Average = Z + y/2

Types of flowchart
 System flowchart – it’s a chart that depicts
the systems as a whole with only
subsystems or major elements shown,
 Program flowchart – this chart shows the
sequence of operations as carried out by a
computer program.

Advantages of flowchart
 Gives programmer good visual reference of
what the program will do.
 Serves as a program or system
documentation.
 It’s easy to trace through from the start to
find the action resulting from a set of
condition.
 Allows programmers to test alternative
solutions to a problem without over coding
the program.

Disadvantages of flowchart
 There are so many different ways to draw
them.
 it’s difficult to remain neat and uncluttered
if the logic is complex.
 Constructing a flowchart is time
consuming.
 They take up considerable space.
 They are difficult to amend without
redrawing.

Comparison between a pseudocode and a flowchart

Program control structures
 They are blocks of statements that
determine how statements are to be
executed. There are three control
structures namely.
Sequence
Selection decision
Iteration (looping) repetition

Sequence
 In this control structure, the computer
reads instructions from a program file
starting from the first top line and
proceeding downwards one by one to the
end. Hence sequential program execution
enables the computer to perform tasks
that are arranged consecutively one after
another in the code.

Example of how a sequential
programs code execute
The
program file
reader
reads
Begin {Procedure name} sequentially
Action 1 statement
Action 2 by
Action n statements
End {Procedure name} to the end
of the file

Selection/decision
 This structure is used to branch, depending on whether
the condition returns a value of True of False (Yes or No).
For example
IF < Condition >
Then Action 1
Else Action 2
Endif.
 There are 4 types of selection controls used in high-level
programming.
 IF……….THEN
 IF……THEN……ELSE
 Nested IF
 CASE SELECTION

IF……….THEN
General format
IF < condition > Then
Statement:
EndIf
If Mark > = 80 then
Print “Reward”
EndIf
 This is used if only one
option is available. All
other options are ignored.
For example if a school
wants to reward only the
students who have mean
mark of 80 and above, it
will be reward only those
students who have
attained 80% and above
and ignore the rest.

IF……….THEN……….ELSE
General Format
IF < Condition > THEN
Statements 1
ELSE
Statements 2
EndIf
The algorithem will be:-
IF fault = Serious THEN
Print “RED CARD”
ELSE
Print “yellow Card”
EndIf
 Used when there are two
available options. For
example in a football
match a player is given a
RED CARD if he does a
very serious mistake
otherwise he is given a
Yellow Card.

Nested IF
 This is used where two or more options
have to be considered to make a selection.
For example, to award grades according
to the marks as follows
a.80 marks Grade A
b.60 marks Grade B
c.50 marks Grade C
d.40 marks Grade D

General format of Nested IF
General Format
IF <Conditions> Then
Statement
ELSE
IF <Condition> Then
Statement
ELSE
IF <Condition>Then
Statement
Endif
Endif
End
The pseudo code segment will be:-
If Marks = 80 THEN
Grade = “A”
ELSE
If Marks = 60 THEN
Grade = “B”
ELSE
If marks = 50 THEN
Grade = “D”
Endif
Endif
Endif
Endif
End

CASE SELECTION
General format
CASEx of
Label 1 : Statement1
Label 2 : Statement2
Label n : Statement n-1
ELSE
Statement n
End case
Example:-
CASE average OF
80…100: Grade=“A”
70…79: Grade=“B”
60…69: Grade=“C”
40…49: Grade=“E”
ELSE
Grade=“F”
End Case
 It’s an alternative to
the nested IF. This
selection is preferred
to the Nested if in
order to reduce the
many line s of codes.
Case selection can
only be expressed
using integers and
alphabetic characters
only. The Boolean
expression should be
CASE integer OF or
CASW char OF

Iteration (looping) repetition
 This is designed to execute the same
block of code again and again until a
certain condition is fulfilled. Iteration is
important in situations where the same
operation has to be carried out on a set of
data many times. There are three main
looping controls.
THE-WHILE-DO LOOP
REPEAT……….UNTIL LOOP
The FOR LOOP

THE-WHILE-DO LOOP
 This repetitive structure tests the condition
first before executing the successful code
if and only if the Boolean expression
returns a true value.
Example
To withdraw money using an ATM a
customer must have a balance in his/her
account.

General format of THE-WHILE DO LOOP
Flowchart General format
While <condition> Do
Statement
End while
Pseudo code segment
While balance >0 do
Withdraw cash
Update account
End while
Withdraw cash
update account

REPEAT……….UNTIL LOOP
 In this structure the code is executed before
testing the condition. The repeat loop stops
when the Boolean statement returns a value. For
example in the case of ATM discussed above
the client can withdraw money until balance is
zero.
Example
Pseudo code segment.
REPEAT
Withdraw cash
Update account
Until balance <0;

General format of REPEAT…………UNTIL LOOP
Flow chart General format
REPEAT
Statement
UNTIL <condition>
Withdraw cash
update account.

The FOR LOOP
 This structure is used where execution of
the chosen statements has to be repeated
a predetermined number of times. For
example if a program is to calculate the
sum of ten numbers provided by the user.
The FOR LOOP can be used to prompt
the user to enter the 10 numbers at most
ten times. Once the numbers are entered
the program calculates and displays the
sum.

Pseudo code of the FOR LOOP
Pseudo code
FOR count = 1 to 10 DO
writeln “Enter a number (N)”
Readln N
Sum = sum + N
End FOR
Display Sum
The counter has to be set to a start value and
sometimes to an end value.

General format of the FOR LOOP
General format
1. format for the FOR LOOP that counts from lower limit.
For loop variables = lower limit To upper limit Do
Statements
EndFor
2. Format for the ‘For’ loop that counts from upper limit
down to lower limit
For loop variable = Upper limit Down To Lower
Limit Do
Statements
EndFor

Flowchart for a For Loop that counts upward
Loop Variable = lower limit Lower limit = Loop
variable + 1
Statement

Flowchart for a For Loop that counts downwards
Loop Variable = Upper limit Upper limit = Loop
variable - 1
Statement

Examples of complex pseudo codes 1
 Ushirika Society pays 5% interest on shares
exceeding Kshs 10,000 and 3% on shares that
do not meet this target. However no interest is
paid on deposits in the member’s bank account.
Design a pseudo code for a program that
would:
a. Prompt the user for shares and deposit of a
particular member.
b. Calculate the interest and total savings.
c. Display the interest and total savings on the screen
for a particular member.

Pseudo code of examples 1
Pseudo code
Start
Input Name, share, Deposit
If share > 10000 THEN
Interest = 0.05*shares
ELSE
Interest=0.03*shares
Endif
Total savings = deposits + Interest + shares
Print Name, Totalsaving, Interest
Stop

Flowchart of example 1
Totalsavings = deposit + shares + interest
Interest = 0.05 * shares
Interest = 0.03 * shares

 Botswana has a population of 3,000,000
but this is falling by 4% each year. The
island of Reunion has a population of
95,000 but this is increasing by 9% each
year.
a. Draw a flowchart that predicts the year in
which the population of reunion will be
greater than that of Botswana if the trend
continues.

Pseudo code of example 2
Pseudo code
Start
Bts: = 3,000,000
1R: = 95,000
Year: = 0
REPEAT
Bts = Bts - (Bts * (4 / 100))
1R = 1R + (1R * (9 / 100))
Year = year + 1
UNTIL 1R > Bts
Print year
Stop

 Write a program that will allow the input of name of
student marks obtained in 5 subjects (maths, English,
Kiswahili, computer, biology). The program should
calculate the total and average marks for each student
and assign the grades depending on the average marks
obtained as follows.
80 – 100 A
70 – 79 B
60 – 69 C
50 – 59 D
Below 50 E
The program should then display each student’s name,
total marks and average grade.

Pseudo code of example 3
Pseudo code
START
REPEAT
Print “Enter name and subject marks”
Input Name, maths, English, Kiswahili,
Computer, Biology
Sum =
Maths + English + Kiswahili +
Computer + Biology
AVG = sum / 5
If (AVG>80) AND (AVG<100) THEN
Grade = ‘A’
Grade = ‘B”
Grade = ‘C’
Grade = ‘D’
ELSE
Grade = ‘E”
Endif
Endif
Endif
Endif
Print Name, Sum, AVG, Grade
Until count = Number of students
Stop

Practical activity 1-1
1. Open a text editor program on your computer like NotePad or
WordPad.
2. Type the following program exactly the way it is in the editor.
<HTML>
<HEAD><TITLE>This is my first a webpage</TITLE></HEAD>
<BODY bgcolor = “red”>
<H1><CENTER><B>Hello World</B></CENTER></H1>
</BODY>
</HTML>
3. Save your work as webpage.html on the desktop. Make sure
that the Save As Type box reads “All Files” before clicking the
save button in order to avoid saving a text file with two
extensions i.e. webpage.html.txt.

Practical activity 1-2
4. Close your text editor. Notice
that your file on the desktop
has the icon of the default web
browser installed on your
computer. Double click it to
view the web page! Figure right
shows a sample of the display
expected when the file is
loaded to the browser. If you
have a colour monitor, it should
look as below only that it will
have black bold text on a red
background!
5. Check your program and
change your background to
blue, save then click the
refresh button. What happens?

Review questions 1
1. Define the term computer program.
2. What is programming?
3. State three advantages of high level languages over low level languages.
4. List four examples of languages and for each, state its most appropriate
application area.
5. Why is an executable file unique when compared to any other file?
6. Differentiate between a compiler and an interpreter. Why did early
computers work well with interpreters?
7. List the various examples of programming languages per generation.
8. State one advantage of machine language over the other languages.
9. Write the following in full
A) HTML
B) OOP
10. Distinguish between source program and object code in programming.
11. Define the term encapsulation as used in object oriented programming.

1. A computer program is a set of instructions that directs a computer on how
to process a particular task.
2. Programming is the writing of computer programs.
3. A). Easier to learn and use.
B). Portable.
C). Flexible.
D). Easier to correct errors.
4. A). FORTRAN – used for developing business oriented programs.
B). COBOL – designed for developing business oriented programs.
C). Pascal – mostly used as a teaching tool in structured programming.
D). C – mostly used to create system software such as operating systems.
E). Ada – suitable for developing real-time and industrial systems.
5. It is the main file that is used to start the program.
6. A complier translates the entire source program into machine readable form
while an interpreter translates the source program to machine language line-
by-line. Interpreters were used on early computers due to memory
limitations.

7. A). First generation – machine languages.
B). Second generation – assembly languages.
C). Third generation – Pascal, C, COBOL, BASIC, FOTRAN, Ada
etc.
D). Fourth generation – Visual Basic, Delphi Pascal, Visual COBOL
etc.
E). Fifth generation languages – PROLOG, Mercury, LISP, OCCAM
etc.
8. A). The processor executes them faster.
B). They are more stable.
9. A). HTML – Hypertext Markup Language.
B). OOP – Object Oriented Programming language
10. Source program refers to a program that is not yet translated while
object code refers to the program code that is in machine readable
form.
11. Encapsulation refers to the process of joining data and instruction
together to form an object.

Review questions 2
1. Give one advantage of compiling a program
rather than interpreting it.
2. Outline at least six stages of program
development in their respective order.
3. Highlight two advantages of monolithic programs.
4. State two advantages of modular programming.
5. In what stage of the development does program
documentation fall? Justify your answer.
6. Differentiate between a flowchart and pseudocode.
7. What is a program bug?
8. Explain why it is important to test a program
before implementing it.

1. A). Interpreters translate the source program one statement at a
time while compilers translate the entire source code at once before
execution.
B). Interpreters translate the program each time it runs hence
slower than compiling. Compiled programs can be saved on a
storage media. This means that it does not require any further
transaction every time the program is run hence executes faster
than interpreted programs.
C). Interpreters translation takes less memory while compiled
programs require more memory as the object code files are larger.
2. A). Problem recognition.
B). Problem definition.
C). Program design.
D). Program coding.
E). Program testing and debugging.
F). Implementation.

3. A). They are difficult to test and debug.
B). They are difficult to modify or upgrade.
4. A). They are easy to test and debug.
B). They are easy to modify and upgrade.
5. Documentation is done at all stages of program
development.
6. A flowchart is a graphical representation of step-by-
step processing logic of a program while a pseudocode
is a set of structured-English like statements that
describe the step-by-step processing logic of a program.
7. Bugs refers to program errors.
8. To correct any syntax or logical errors.

Review questions 3
1. State the factors you would consider when
A) Writing a pseudocode
B) Drawing a flowchart
2. Using illustrations, explain at least six symbols used in
flowchart design.
3. Give one advantage of pseudocodes over flowcharts.
4. Write a pseudocode for a program that would be used
to solve the equation
E = MC2
5. Draw a flowchart that would be used to classify animals
according to sex. If a letter M is input the program
should display ‘Male’ otherwise it should display
‘Female’.

1. A). Pseudocode
1). Statements must be short
and clear.
2). Statements should be
unambiguous.
3). Should shoe start and stop.
4). Words used should be
suggestive such as READ,
PRINT, OUTPUT etc.
B). Flowchart
1). A flowchart should have
one entry and one exit point.
2). Use correct symbols.
3). The flow should be clearly
indicated using arrows.
2. Decision – used to represent
a decision construct.
Connector – connects logic
flows.
Process – indicates a
transformation of data.
Input/output – shows
program input/output.
Ellipse – indicates start/stop
of algorithm.

3. Pseudocodes are
easier to write and
understand.
4. Start
Enter values form
M and C
E=M*C*C
Display E
Stop

Review questions 4
1. Define the term selection in relation to program
control structures.
2. State three types of control structures used in
programming.
3. Differentiate between looping and selection.
4. In what circumstance does looping depend on
decision?
5. List four selection controls used in writing a
program.

1. Selection refers to a situation where further program execution
depend one making a decision from two more alternatives.
2. Sequence, decision and iteration.
3. Looping refers to a situation where the same block of code is
executed repeatedly until a certain condition is fulfilled, while
selection refers to a situation where further program execution
depends on making a decision from two or more alternatives.
4. Looping may depend on decision if a condition has to be met
before the looping terminates or continues.
5. A). IF…THEN
B). IF….THEN…ELSE
C). Nested IF
D). Case

1. State three reasons why high level languages are better than low level
languages.
2. Explain why HTML is not true programming language.
3. List three examples of forth generation programming languages.
4. Describe the term structured programming.
5. Define the term structured programming.
6. A). State two reasons for documenting all the stages of program
development.
B). Give three types of program documentation in reference to
programming.
7. Write HTML code that would display a green background, with the words
‘Hello’ on the screen.
8. Draw a flowchart showing the general flow of the following:
A) The nested IF selection.
B) The FOR loop.
C) REPEAT….UNTIL loop.

Answer of revision questions 1-1
1. A). They are portable
B). They are user friendly
C). They are more flexible
D). They are easier to debug
2. HTML is not a true programming language because it does not have
a true format of a programming language. For example, it does not
have a declaration part and control structures.
3. A). Visual Basic
B). Delphi Pascal
C). Visual COBOL
4. Fifth generation programming languages are designed in a way that
enables programmers design programs that emulate human
intelligence.
5. In structured programming, a program is broken down into
components called modules each performing a particular task.

6. A). Reasons for documenting
i. There may rise a need to revise or modify it.
ii. Other people may think of ways of improving your program by
studying at the documentation.
B). Types of documentation
i. User-oriented.
ii. Operator-oriented.
iii. Programmer-oriented.
7. <HTML>
<HEAD><TITLE>Hello program </TITLE></HEAD>
<BODY bgcolour = “blue”>
<H3><CENTRE><B>Hello</B></CENTER></H3>
</BODY>
</HTML>

1. Write a program algorithm that would enable the user
to enter student marks. The program should then
determine whether the mark entered is a pass or fail
given that the pass mark is 50.
2. Draw a flowchart for a program that is to prompt for N
numbers, accumulate the sum and then find the
average. The output is the accumulated totals and the
average.
3. Write a pseudocode that reads temperature for each
day in a week, in degree Celsius, converts the Celsius
into Fahrenheit's and then calculate the average
weekly temperatures. The program should output the
calculated average in degrees Fahrenheit's.

3. START
Input temperature in ℃
et initial day to 0
WHILE initial day 6 DO
Input temperature in ℃
F=32+(9C/5)
Initial day=initial day + 1
Cummulative = cummulative + F
END WHILE
Average weekly temperature
= cummulative/7
Print Average
STOP

1. A lady deposits 2,000 shillings in a Microfinance
company at an interest rate of 20% per annum. At the
end of each year, the interest earned is added to the
deposit and the new amount becomes the deposit for
that year. Write an algorithm for a program that would
track the growth of the deposits over a period of seven
years.
2. Mukumu took a loan of Ksh 400,000 from a local bank
at an interest rate of 10% payable in four years.
Assuming you wish to develop a computer program
that will keep track of monthly repayments:
A) Identify the input, processing and output
requirements for such a program.
B) Design the algorithm for the program using a simple
flowchart and pseudocode.

1. START
Input initial deposit
Input interest rate
Set deposit to initial deposit
Set year to 0
WHILE year < 7 DO
Interest = Deposit * interest rate
Total = Deposit + interest
Deposit = Total
Year = Year + 1
END WHILE
PRINT Deposit, Year
STOP

2. A).
Inputs – initial amount borrowed
- Interest rate
- Number of years
Processing – the equation to calculate
monthly repayments.
Output – monthly repayments calculated
by the process

2. B).
START
Input initial loan borrowed
Input interest rate
Input number of years
Calculate yearly
repayments
Monthly repayments
= yearly repayments/12
Display monthly
repayments
STOP

289
Chapter 4
System development

A system
 Is a set of items linked together to carry
out a given task in order to achieve one or
more objectives. A system is described as
being either soft or hard.

Soft systems and hard systems
 Soft systems – human activity are said to be
soft systems. They are said to be soft
because:
 Their boundaries may be fluid or keep on changing.
 Their goals and objectives conflict.
 It’s difficult to precisely define exact measures of
performance for them.
 Hard systems – these are systems whose
goals and objectives are clearly defined and
the outcomes from the systems processes are
predictable and can be modeled accurately.

System classification
 Deterministic system – these are systems whose
output are known precisely by their inputs e.g. a
computer system.
 Probabilistic system – these are systems whose
output can only be predicted but not knows
precisely e.g. business and economic system
organisation.
 Cybernetic systems – these are self controlling
systems which adapt to the environment and
regulate their own behaviour by accessing the
feedback. They access their output and adjust
the input e.g. human beings, plants systems

Characteristic of systems
1. Holistic thinking
2. Sub systems
3. Processor
4. Objectives/purpose
5. Environment
6. Boundaries
7. Interdependence
8. Feedback
9. Control
10. Inputs and Outputs
11. System Entropy

Holistic thinking and sub systems
 Holistic thinking – in this, a system is considered
as a whole. A combination of various
components that makes up a system creates a
complex whole whose overall goals are more
sophisticated than those of the individual
components.
 Sub systems – a system is made up of different
components (subsystem). Therefore a system
does not exist in solitude but it may be a
component of a large system.

Processor and objectives/purpose
 Processor – this is an element of a system
that does the actual transformation of input
into output.
 Objectives/purpose – objectives of a
system may be real or stated. An
organization should state one objective
and operate to achieve another user must
know the major objective of a system.

Environment and boundaries
 Environment – the environment is the
system within an organisation operates.
Environment provides a reason for the
existence of the system.
 Boundaries – system boundaries are the
external element whose changes in
attitudes, behaviour and property affect
their state and are affected respectively i.e.
it’s the limit of system.

Interdependence and feedback
 Interdependence – for a system to be
effective and efficient, its components or
subsystems must be coordinated and
linked together.
 Feedback – a feedback is a check within a
system to see whether predetermined
goals are being met. The checks are
conducted on a system to determine
deviation.

Control and inputs and outputs
 Control – this is the
process by which the
system adapts to
changes in the
environment in order to
give the expected level.
 Inputs and outputs – a
system communicates
with its environment by
receiving inputs and
giving outputs.

System Entropy
 Entropy means decay. System ‘decay’
naturally over time, hence it slowly
becomes useless to the user either due to
improvement in technology, new
management or change in user
requirements. Therefore it must be
reviewed in order to improve it or develop
a new one.

Open and closed system
 An open system receives input from and
gives output to the environment while a
closed system does not interact with the
environment.

Information system
 This is a set of persons, procedures and
technologies and other resources that
collects, transforms and disseminates
information in the system e.g. organisation.

Purpose of information system
 To provide the people within an
organisation with information to assist in
decision making process.
 To provide responsive service to meet
user needs.
 To enable sharing of information.
 To facilitate interaction and dissemination
of data throughout the various level of
organisation.

Why develop new information system?
 New changes in organisation – management
can introduce new changes, and they have to be
implement to meet the needs of the organisation.
 Problems in the current system – the
undesirable circumstances in the current system
that prevent the organisation from meeting its
goal.
 New opportunities – if an opportunity presents
itself that can enable the organisations improve
its services.

Theories of system development
 The most common theories include:
Traditional Approach.
Rapid Application Development (RAD).
The Structured Approach.

Traditional Approach
 This approach relies mostly on the skills
and experience of individual staff
members carrying out of the project. In this
approach, the manual system is replaced
with a computerized one without change in
overall structure of the former system.
Hence the weakness of the former system
are not addressed, they are forwarded to
the new system.

Rapid Application Development (RAD)
 RAD model evolved from the theory that
business today heavily rely on information
technology, hence, development and
implementation of information system
needs to be quick enough for the
organisation to maintain a competitive
advantage in the market place.

Structured Approach
 In this approach a system development
defines a set of stages that should be
followed when developing a system.

Stage of system development
 Problem recognition
and definition
 Information gathering
 Requirements
specification
 System design
 System construction
 System
implementation

Problem recognition and definition
 Problem recognition is the initial stage where the analyst
decides if the project is really necessary to look into, and if its
necessary to start a new project. In problem definition, the
problem must be thoroughly defined. A through survey of the
problem is undertaken by identifying the problem,
understanding it, and finding out of there is a possibility of
getting a solution. Before a new system is designed, a special
study will be carried out to establish the costs and benefits of a
new system. The study is called feasibility study. Feasibility
study of a system is accessed in four ways.
 Operational feasibility
 Technical feasibility
 Economic feasibility
 Schedule feasibility

Operational feasibility and technical feasibility
 Operational feasibility – this establishes
the extend to which the users are
comfortable or happy with the proposed or
new system.
 Technical feasibility – this establishes
whether the technology available is
sufficient or can be upgraded for the new
system.

Economic feasibility and schedule feasibility
 Economic feasibility – it establishes
whether the technology available is
sufficient or can be upgraded for the new
system.
 Schedule feasibility – it establishes
whether the development of the proposed
system will be accomplished within the
available time.

Information gathering
 The system analyst gathers data about the
current system and the users needs from
both internal and external sources. Some
of the methods used to collect or gather
data include:
Record inspection
Interview
Questionnaires

Record inspection and interview
 The documents maintained
in connection to the system
are referenced. This forms a
good starting point for the
analyst to gain an overall
insight of the existing system.
 Interview – this is a face to
face communication between
the analysts as the
interviewer and the affected
personnel as interviewee.
The questions are geared to
getting the information
needed by the analysts.

Advantages of interview
 The analysts is accessible to first class
information.
 Make interviewee feel as part of the
system.
 Give adequate opportunity for interviewee,
an opportunity to put forward opinions.

Disadvantages of interview
 Make the interviewee feel they are being
summoned by the analysts.
 Some interviewees give answers which
are not actually proven facts but opinions.
 The interviewee may not fully open on
some issues that may be personal.
 The interviewee may be suspicious of the
intentions of the proposed system for fear
of being displaced by new system.

Questionnaires
 A questionnaire is a
document containing a
number of standard
questions set to be asked
to a larger number of
people in order to gather
information from them. The
analyst is able to collect
information from several
key people in the
organisation who may be
affected by the current
proposed system.

When the use questionnaire
 When limited amount of information is
required from a large number of people.
 There is a large number of people involved
in the system project.
 The people you need to gather information
from are vastly despersed.

Advantages of questionnaires
 Answers filled in less tense environment.
 Since they are filled and returned in
privacy, more sincere responses are
possible.
 Questionnaire provides many people with
the opportunity to provide input and
suggestion.
 Questionnaire saves time especially where
respondents are geographically scattered.

Disadvantages of questionnaires
 It’s a slow way of facts gathering.
 Designing questionnaires requires
expertise.
 Some questions can be easily
misunderstood hence ambiguous replies
will be received.
 Analysis of questionnaires requires a lot of
time.

Observation
 This requires the observer to participate or
watch closely as a person performs
activities in order to learn about the
system. This method gives the analysts
first hand experience about the problems
and expenses to the system requirements.

Advantages of observation
 Concepts that are too difficult for non-
technical staff to explain can be observed.
 It helps the analysts become acquainted
with operational personnel.
 It helps the analysts acquire ‘know how’
needed to assist in changes that have
been recommended.
 Can correct ‘hazy’ understanding or
erroneous impressions.

Disadvantages of observation
 It’s costly and time consuming.
 Staff members are not comfortable when
they are being watched.

Automated method
 This is mostly used when actual data is
required but difficult to get through
interviews, observation or questionnaires.
Such data is collected using devices that
automatically capture data from the source.
E.g. video, cameras, tape recorders etc.

Requirements specification
 The system analyst must come with the
detailed requirements for the new system.
The requirements specifications include:
Output specification
Input specification
File/data stores
Hardware and software requirements

Output specification
 The output specifications entails activities
like generation of reports used to facilitate
decision making. The output can be in the
form of reports either in hardcopy or
softcopy. The quality of those reports is
important. Formality of reports is important
so that good quality reports are produced
for easy understanding.

Input specification
 The input to the system in necessary
because the contents of the input are used
to maintain the master files. The following
should be considered in input specification.
The contents and volume of input.
The mode and devices of input selected.
Layout and sequence of input.

File/data stores
 File requirement involves making an
informed decision on file required to store
data and information in the system. The
analyst should identify the number of files
that will be needed by the system and
determine the structure of each file.

Hardware and software requirements
 System analyst should specify all
hardware and software requirements for
the new system. He/she should consider:
Economic factors e.g. price
Operational factors e.g. reliability
User friendliness.

System design
 This involves detailing the physical design
of the system, it’s the how of the process.
Once the logical design is put lined during
system analysis, the analyst determines
the physical design, which describes the
hardware, software and operating
procedures required to make system
operational. Several tools are used for
designing an information system.
Examples are flowchart, data flow diagram,
requirements.

System construction
 This refers to coding, installation and
testing of the modules and their
components such as outputs, inputs and
files. The purpose of the construction is to
develop and test a functional system that
fulfills the business and design
requirements.

Testing the system
 The system is tested by entering some
test data to find out whether its output are
as expected. The system is tested using
the requirements specifications and the
design specification to find out whether it
meets all requirements specified.

System implementation
 This involves installing the system in the
user’s computers, testing the installed
system, converting from old system to the
new one and training the users. System
implementation involves:
File creation and conversion.
Change over.
Staff training

File creation and conversion
 This involves setting up of the master files
that are to be used in the support of the
new system. The setting can be either
from scratch or just to convert the files that
were employed in old system.

Training staff
 The training aim at:
Convincing the staff of the user department
on the effectiveness of the new system.
Remove fear of change from them.
Enabling the staff to cope with processing
task of the new system.

Methods of training
 Demonstration
 Film show
 Manual reference
 Group discussion
 Visits

Changeover
 This is the process of changing over from
old system to the new system.
 Type of changeover
Direct changeover
Parallel changeover
Phase changeover

Direct changeover
 In this approach the new system commence live
operation and immediately the old system is
abandoned.
 Advantage of direct changeover
 It’s a cheap method
 Disadvantages of direct changeover
 Extremely risky
 Places an organization in a do or die situation.

Parallel changeover
 In this changeover the operation of the old
system and the new system run alongside each
other.
 Advantages of parallel changeover
 Provides a method of training in the new system.
 Personnel become familiar with the new system prior
to actual changeover.
 Disadvantages of parallel changeover
 Costly to run two systems
 Cross checking is difficult
 Requires more staff hence more training required for
additional staff

Phase changeover
 In this approach implementation is done only
one part of the new system at one time or a step
by step.
 Advantages of phase changeover
 Allow the system to be implemented quickly
 Less costly
 Failures of the system are limited
 Causes minimal disruption
 Disadvantage of phase changeover
 Problems on ensuring that the first phase is
implemented and converted.

System review and maintenance
 System maintenance is the adjustment
and enhancement or correction of errors
after the system has been implemented.
The reviewing involves going through the
specification and testing the system after
implementation to find out whether it still
meets the original specification.

System documentation consists of
 Report of fact finding which outlines methods used to collect data,
weakness of the current system and recommendation of the current
system.
 Requirements specification which entails the output requirements, input,
hardware and software required for the new system.
 System flowchart which shows the overall functionality of te proposed
information system.
 Tables or file structures depending on the approach used in system
construction.
 Sample test data to test whether the new computerized information
system is working as expected.
 User manual which helps the user work with the new system with
minimal guidance. The manual contains information like
 How to install, start the system
 The interface of the system
 How to carry out various tasks
 Error correction and how to get help

Review questions 1
1. Define the term information system.
2. Differentiate between soft systems and hard
systems.
3. List five characteristics of a system.
4. What is system control?
5. Why do we need feedback in a system?
6. Explain the tem system boundary.
7. State and explain three purposes of information
systems in organisations.
8. Define the term online analytical processing?
9. Draw a well labelled diagram that depicts a
system that is controlled through feedback.

1. An information system is the arrangement of people, data,
processes and information that work together to support and
improve the day-to-day business operations.
2. In soft systems, goals are not clearly defined unlike in hard systems.
3. A). Holistic thinking
B). Subsystems.
C). Boundary and environment.
D). Purpose.
E). Process.
F). System entropy.
G). Inputs and outputs.
H). Open and closed systems.
I). Control
4. A system control is a method by which a system adapts to changes
in the environment in order to give the expected output or perform at
the expected level.

5. Feedback is needed in order
to adjust controls for better
performance of the system.
6. System boundary is the
scope within which a system
component operates.
7. A). Supports information
processing tasks.
B). Supports decision making.
C). Supports sharing of
information.
8. Online analytical processing
is whereby a computer based
information system is used to
capture operational data,
analyse and generate reports
to be used for supporting
decision making process in
an organisation.
9. .

Review questions 2
1. Explain three system development theories and methods.
2. State the main disadvantage of Rapid Application Development
method.
3. Define the term system development lifecycle.
4. At what stage does the system change hands from the development
stage to the users.
5. Highlight three circumstances that necessitate the development of
new information systems.
6. Define the term feasibility study as used in system development.
7. State four methods that can be used to gather information during
system development.
8. State two advantages of interview over questionnaires.
9. State two disadvantages of interview method when used for
information gathering.
10. Give one example of automated information gathering technique.

1. A). Traditional approach.
B). Rapid Application
Development (RAD)
C). Structure approach.
2. The main disadvantage of
RAD is that the system may
be weak due to quick
development.
3. System development life
cycle refers to the steps
followed in developing a
system for conception to
review and maintenance.
4. At the implementation stage.
5. A). New opportunities.
B). Problems
C). Directives.
6. Feasibility study is a special
study carried out to establish
the costs and benefits of a
new system.
7. A). Interviews
B). Questionnaires
C). Observation
D). Study of available
documents.
E). Automated methods.

8. A). Non-verbal communication can be used or
observed.
B). Questions can be rephrased for clarity.
9. A). It is difficult to organise for an interview due
to time constraint.
B). The interviewee may not fully open up
some sensitive issues due to security concern.
10. An example of automated information gathering
technique is the use of a video camera to
compare motion pictures.

Review questions 3
1. Outline the four areas that are considered
during the requirements specification stage.
2. Explain at least three factors that should be put
into consideration during output design.
3. State four factors that may be considered in
order to design a good file.
4. Explain why it is important to consider file
backup and recovery strategies during file
design.

1. A). Output
B). Input
C). Files
D). Hardware and
software requirements.
2. A). Target i.e. the
audience.
B). Frequency of report
generation
C). Quality and format
3. A). Record key field
B). Type of data
C). Length of each field
D). Backup and recovery
strategies.
4. Back up and recovery
strategy helps in making
sure that if the current
file gets corrupted, it is
possible to reconstruct
the original file.

1. Outline seven steps followed in structured system
development.
2. Explain three tasks that are carried out during system
implementation.
3. Outline three disadvantages of questionnaires.
4. Explain the concept of proxemics in interviews.
5. Give an advantages of straight changeover over parallel
changeover.
6. Define the term file conversion.
7. Differentiate between a system flowchart and a program
flowchart.
8. Draw four system flowchart symbols and explain their
functions.

1. A). Problem recognition and
definition.
B). Requirement
specification.
C). System design.
D). System construction.
E). System implementation.
F). System review and
maintenance.
2. A). File conversions.
B). Staff training.
C). Project management.
D). Changeover
3. A). Good questionnaires
are difficult to prepare.
B). The respondent may
not understand some
questions.
C). The respondent has
the final say on when to
fill and return the
questionnaire. Most of
them end up not being
filled or returned hence it
is disadvantageous to
the researcher.

4. Proxemics refer to issues
related to physical contact
such as sitting arrangement
during an interview.
5. Straight changeover is
cheaper to implement than
parallel changeover.
6. File conversion refers to
changing files from one format
to another.
7. A system flowchart is for the
entire system while a program
flowchart is for a part or a
module in the system.
Therefore, several program
flowcharts may be derived
from a single system flowchart.

1. Define the term “attribute”.
2. Explain the importance of using automated methods in
fact finding.
3. Why is observation sometimes disadvantageous when
used in fact finding?
4. State one of the disadvantages of the traditional
approach in system development.
5. Outline the factors that should be considered when
sourcing for hardware and software resources required
for a new system.
6. Outline some of the contents of a user manual that
would help the user run the system with minimal
guidance.

1. Entity attributes refer to characteristics of a particular entity.
2. Automated methods of data collection can be used in areas which
are not easily accessible.
3. A). The person being observed might alter his or her behaviour.
B). It may be time consuming.
4. The weaknesses of the former system are not addressed.
5. A). Economic factors.
B). Operational.
C). Services from the vendor.
6. A). Installation procedures.
B). User interface.
C). How to carry out various tasks.
D). Test data and expected output
E). Troubleshooting guide

Practical exercise 1
 Extract the book
return module
flowchart from the
system flowchart
depicted in figure right.

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