Pseudo code.pptx

Computers and Logic
• Logic is the study of various principles or
tools of correct reasoning and of the
application of those tools in solving
problems.
• To complete a computer task, all of the
reasoning required to perform that task must
be done by the programmer and entered into
the computer in the form of a computer
program.
• a good understanding of logic is valuable in
helping the programmer to avoid
programming errors and to produce

Computers and Logic
• The tools of logic are very helpful in
analyzing, or breaking down, such problems
into simple steps and simple instructions.
• This analysis is important because
computers can understand only very simple
instructions.

Understanding the Programming Process
• A programmer's job involves writing
instructions and can be broken down into
six programming steps :
1. Understand the problem.
2. Plan the logic.
3. Code the program.
4. Translate the program into machine
language.
5. Test the program.
6. Put the program into production.

Understanding the Programming
Process
1. Understanding the Problem: a
Professional computer programmers write
programs to satisfy the needs of others.
• Note: Really understanding the problem
may be one of the most difficult aspects of
programming.
2. Code the Program : The heart of the
programming process lies in planning the
program's logic.

Process
• During this phase of the programming
process, the programmer plans the steps to
the program, deciding what steps to include
and how to order them.
• The two most common tools are flowcharts
and pseudocode. Both tools involve writing
the steps of the program in English.
• Note: " An algorithm is the sequence of
steps necessary to solve any problem.”

Process
3. Code the Program : write the program in
one of more than 400 programming
languages.
4. Translate the Program into Machine
Language:
5. Test the Program : Selecting test data to
test program and ensure that the program
is free of syntax errors and free of logical
errors.
6. Put the Program into Production :Once
the program is tested adequately, it is ready

Algorithms
• Algorithm is a set of rules applied to
numbers written in decimal form. The word
is derived from the phonetic pronunciation
of the last name of Abu Ja'far Mohammed
ibn Musa al-Khowarizmi, who was an
Arabic mathematician who invented a set of
rules for performing the four basic
arithmetic operations (addition,
multiplication , subtraction, and division)
on decimal numbers.

Algorithms
• An algorithm is a set of rules or
instructions for doing a task or solving a
problem.
• It is a step-by-step series of instructions
wherein each successive step is determined
by the outcome of previous steps.
• A computer program is simply an
algorithm for a computer that is written in
a programming language.
• These algorithms can be designed though
the use of flowcharts or pseudocode.

Algorithms
• Both the pseudocode and flowchart in
algorithm should always have a Start step
at the beginning and at least one Stop step
at the end.

Flowcharts
• Flowcharts are graphic representations of
algorithms. they form an intermediate step
between human understanding of the task to
be accomplished and the coded program
that directs a computer to complete the
various steps of the task.
• A flowchart is a diagram made up of boxes,
diamonds and other shapes, connected by
arrows - each shape represents a step in the
process, and the arrows show the order in
which they occur.

Flowcharts
• Flowcharting combines symbols and
flowlines , to show figuratively the
operation of an algorithm.
• Flowcharts be essential in developing and
understanding the task.

Standard Symbols
used in
Flowcharts

The Terminal Symbol
• The terminal symbol indicates the
beginning and the end of processing. It
contains the word START, STOP, or END.
• It represented by rounded rectangles .

The Input / Output Symbol
• The input/output symbol (or I/O symbol)
indicates that the computer is to obtain new
data or to record the results of
computations.
• This symbol often contains directions to
read records or to print report lines.
• It represented by parallelograms.

The Decision Symbol
• The decision symbol represents a branch in
the flow of a program; it must contain
directions that indicate which branch to
follow. It represented by Diamond .
• This symbol usually contains a question,
and each of its branches is labeled with an
answer.

The Process Symbol
• The process symbol contains instructions
that are not represented by other symbols.
• Process symbols usually contain directions
for calculations or for the storage of data.
• It represented by rectangles.

Flow direction lines
• Flow direction lines indicate the flow of
the program.

Comments
• The comment or annotation symbol is
used to annotate other entries.
• The dashed line indicates the position of the
comment.

The Connector Symbol
• The connector is used to join areas of a
flowchart, in the other word allows you to
connect two flowchart segments.
• A connector represented by a Small Circle .
• The connector is used only when points to
be joined occur on the same page.

The Striped Symbol
• The striped symbol is used to represent a
predefined process (or series of operations)
when the flowcharts that define the process
are included with the current set of
flowcharts.

The Predefined Process Symbol
• The predefined process symbol or Model
symbol is used to represent a predefined
process when the flowcharts that define the
process are not included with the current set
of flowcharts.
Example: START
END
Read Input.
Call calc_pay
function.
Display results.

The off-page Connector Symbol
• The off-page connector is used to join
areas of a flowchart when the points joined
occur on different pages.

General Rules for flowcharting
1. All boxes of the flowchart are connected
with Arrows. (Not lines)
2. Flowchart symbols have an entry point on
the top of the symbol with no other entry
points.
3. The exit point for all flowchart symbols is
on the bottom except for the Decision
symbol.
4. The Decision symbol has two exit points;
these can be on the sides or the bottom and
one side.

5. Generally a flowchart will flow from top to
bottom.
6. Connectors are used to connect breaks in
the flowchart. Examples are:
• From one page to another page.
• From the bottom of the page to the top of
the same page.
7. Subroutines have their own and
independent flowcharts.

8. All flow charts start with a Terminal or
Predefined Process subroutines symbol.
9. All flowcharts end with a terminal or a
contentious loop.

Any program using flowchart would be
1. Start.
2. Read some information.
3. Make a decision.
4. On the basis of that decision
, carry out one process or the
other.
5. Print a result in either case.
6. Stop.

Four Flowchart Structures
• Sequence
• Decision
• Repetition
• Case

32
Sequence Structure
• A series of actions are performed in
sequence.

33
Decision Structure
• One of two possible actions is taken,
depending on a condition.

34
Repetition Structure
• A repetition structure represents part of
the program that repeats. This type of
structure is commonly known as a loop.

35
Pre-Test Post-Test

36
• In Pre-Test Repetition Structure The
condition is tested BEFORE any actions
are performed.
• In Post-Test Repetition Structure The
condition is tested AFTER the actions
are performed.
x < y? Display x Add1 to x
YES
Display x
Add 1 to x
YES
x < y?

37
Case Structure
• One of several possible actions is taken,
depending on the contents of a variable.

38
Case Structure
• Example:
CASE
years employed
1 2 3 Other
bonus = 100 bonus = 200 bonus = 400 bonus = 800
If years employed = 1,
bonus is set to 100
bonus is set to 200
bonus is set to 400
If years employed is
any other value, bonus
is set to 800

Exercise _ 1
• Design an Flowchart to convert a
temperature in degrees Fahrenheit to
degrees Celsius.
• Hint: Celsius = 5/9 * (Fahrenheit – 32).
Start
Read Fahrenheit
Celsius = 5/9 * (Fahrenheit – 32)
Output
Celsius
End

Exercise _ 2
• Design an Flowchart that accepts two
numbers and computes their sum,
difference, product, and quotient.
Start
Read Num1
Read Num2
Sum = Num1 +Num2
Difference = Num1 - Num2
Product = Num1 * Num2
Quotient = Num1/Num2
Print Sum
Print Difference
Print Product
Print Quotient
END

Exercise _ 3
• You work in a store that sells imported
fabric. Most of the fabric you sell is
measured in square yards, but your
customers want to know the equivalent
amount in square meters. Design an
Flowchart to perform this conversion.
Hint: 1 square meter
= 1.198 yards.
Start
Read value in Yard (Y)
Square meter Value (S) = Y/1.198
Output S
END

Exercise _ 4
• Design an Flowchart that computes the
employee’s gross salary given the hours
work and the hourly rate. Assume that 15%
of the salary is deducted as taxes.
Start
Read Hours Work (H)
Read Hourly Rate (R)
Gross Salary = H * R
Tax = (15/100) * Gross Salary
Net Salary = Gross Salary - Tax
Print Net
Salary
END

Exercise _ 5
• Design an Flowchart that computes the
distance between two points (X1, Y1) and
(X2,Y2).
• Hint: Distance =
Start
Read X1
Read X2
Read Y1
Read Y2
Z1 = (x1 – x2)^2
Z2 = (y1 – y2)^2
Distance =
Output Distance
END

Exercise _ 6 _Assignment_ 1
• Ann likes to jog in the morning. As she
jogs, she counts the number of strides she
makes during the first and the last minutes
of her jogging. Anne then averages those
two and calls this the number of strides she
makes in a minute. Design an flowchart that
accepts those averages and the total time
she spent jogging (in hours and minutes)
and then outputs the distance Ann jogged in
miles. Assume that Ann’s stride to be 2.5
feet.
• Hint: 1 mile has 5280 feet.

Start
Read Average
Read Hours
Read Minutes
Total Minutes = (Hours * 60) + Minutes
Total number of Strides = Total Minutes * Average
Feet Total = Total Strides * 2.5
Miles = Feet Total / 5280
Output Miles
END

Pseudo code
How to write pseudo code

What is a Pseudo code ?
• Pseudo code is an approximate
language between the natural language
and computer code.
• Pseudo code is English phrases or lines
of statements that used to solve specific
problem by using short commends.

Why a Pseudo code called by this
name?
• Because it is not programming
language so, computer didn’t
understand this language .
Why a Pseudo code used ?
• Because after making pseudo code , its
very easy to make code by any
programming language .

There are six basic computer operations
1. A computer can receive information
Read (information from a file)
Get (information from the keyboard)

2. A computer can put out information
Write (information to a file)
Display (information to the screen)

3. A computer can perform arithmetic
Use actual mathematical symbols or the
words for the symbols
- Add number to total
- total = total + number
Note: you use ( +, -, *, / )
Calculate, Compute also used.

4. A computer can assign a value to a
piece of data
3 cases:
To give data an initial value
Initialize, Set
To assign a value as a result
x = 5 + y
To keep a piece of information
for later use
Save, Store

5. A computer can compare two piece of
information and select one of two
alternative actions
IF condition THEN
some action
ELSE
alternative action
ENDIF
1.

6. A computer can repeat a group of
actions.
The Repetition structure can be
implemented using :
• Repeat Until Loop.
• The While Loop.
• The For Loop.

• The Repeat Until loop, The syntax is
REPEAT
A statement or block of statements
UNTIL a true condition
----------------------
• The While loop, The syntax is
WHILE condition (is true)
some action
ENDWHILE
----------------------

• The For Until loop, The syntax is
FOR a number of times
some action
ENDFOR

Control Structures
or Logical
Structures

• It is possible to write any computer
program by using only three basic control
structures:
1. Sequence,
2. Selection,
3. Repetition.

1. Sequence :
Execution of one step after another.
This is represented as a sequence of
pseudocode statements:
Statement 1
Statement 2
Statement 3
Example: Read three numbers
Add three numbers
Display total of three numbers
•

• Note : The sequence structure in flowchart is
the logical equivalent of a straight line in
pseudocode.
• Example :

2. Selection
• Presentation of a condition and the choice
between two actions,
• the choice depending on whether the
condition is true or false. In pseudo code,
selection is represented by the keywords
IF, THEN, ELSE and ENDIF
IF condition p is true THEN
statement(s) in true case
ELSE
statement(s) in false case
ENDIF

• Example:
IF student is part-time THEN
Add one to part-time-count
ELSE
Add one to full-time-count
ENDIF

• The Selection structure in flowchart
and the equivalent of it in pseudocode.

3. Repetition
Presentation of a set of instructions to be
performed repeatedly, as long as a
condition is true.
WHILE condition p is true
Statement(s) to execute
ENDWHILE
Note:
• The condition is tested before any
statements are executed.

• Example: Set student_total to 0
WHILE student_total < 50
Read student record
Print student name and address
Add 1 to student_total
ENDWHILE
• Note:
• The variable student_total is initialized
before the loop condition is executed.
• The student_total variable is
incremented within the body of the loop.

• Example:
Write a program that obtains two integer
numbers from the user. It will print out
the sum of those numbers.
Answer is :
1. Prompt the user to enter the first integer.
2. Prompt the user to enter a second
integer.
3. Compute the sum of the two user inputs.
4. Display an output prompt that explains
the answer as the sum.
5. Display the result.

Exercise _ 1
• Design an pseudocode to convert a
temperature in degrees Fahrenheit to
degrees Celsius.
• Hint: Celsius = 5/9 * (Fahrenheit – 32).
• Answer:
1. Start.
2. Get F (Fahrenheit’s degree) .
3. Celsius = 5/9 * (F – 32).
4. Output Celsius .
5. Stop.

Exercise _ 2
• Design an pseudocode that accepts two
numbers and computes their sum,
difference, product, and quotient.
• Answer:
1. Start.
2. Sum=0, Difference=0 , Product=0 ,
Quotient = 0 ;
3. Get the First number.
4. Get the Second number.
5. Add First number and Second
number to Sum.

Exercise _ 2
6. Difference=First number - Second
number .
7. Product=First number * Second
number .
8. Quotient = First number / Second
number .
9. Output (Print or display ) Sum.
10. Output Difference.
11. Output Product.
12. Output Quotient .
13. Stop.

Exercise _ 3
• You work in a store that sells imported
fabric. Most of the fabric you sell is
measured in square yards, but your
customers want to know the equivalent
amount in square meters. Design an
pseudocode to perform this conversion.
Hint: 1 square meter
= 1.198 yards.
• Answer:
1. Start.
2. Get Y (number value in yard).

Exercise _ 3
3. S (square meter value ) = Y / 1.98 .
4. Output S.
5. Stop.

Exercise _ 4
• Design an pseudocode that computes the
employee’s gross salary given the hours
work and the hourly rate. Assume that 15%
of the salary is deducted as taxes.
• Answer:
1. Start.
2. Get H (hours work ).
3. Get R (hourly rate ) .
4. Gross Salary = H * R .
5. Tax = (15/100)* Gross Salary .

Exercise _ 4
6. Net Salary = Gross Salary - Tax .
7. Output Net Salary .
8. Stop.

Exercise _ 5
• Design an pseudocode that computes the
distance between two points (X1, Y1) and
(X2,Y2).
• Hint: Distance =
• Answer:
1. Start.
2. Get X1.
3. Get X2.
4. Get Y1.
5. Get Y2.

Exercise _ 5
6. Z1 = (X1 – X2)^2
7. Z2 = (Y1 – Y2 )^2
8. Distance =
9. Output Distance.
10.Stop.

Exercise _ 6
• Design an pseudocode and the
corresponding flowchart for adding the test
scores as given below: 26, 49, 98, 87, 62, 75
• Answer of pseudocode:
1. Start;
2. Sum = 0 ;
3. Get Test score _1;
4. Add Test score _1 to Sum ;
5. Get Test score _2 ;

Exercise _ 6
7. Get Test score _3;
9. Get Test score _4 ;
10.Add Test score _4 to Sum ;
11.Get Test score _5 ;
13.Get Test score _6 ;
15.Output Sum ;
16.Stop ;

Exercise _ 6

Exercise _ 7
• The problem with Exercise_6 have some
steps appear more than once, i.e. step 5 get
second number, step 7, get third number,
etc. One could shorten the algorithm or
flowchart as follows:
• Answer:
1. Start
2. Sum = 0
3. Get Value
4. Sum = Sum + Value

Exercise _ 7
5. Go to step 3 to get next Value
6. Output Sum
7. Stop
• Answer of flowchart:

Exercise _ 8
• In Exercise_6, step 3 to 5 will be repeated,
where a number is obtained and added to
the sum . So, we can use repetition structure
to represent the answer by adding terminal
value to end loop .
1. Start
2. Sum = 0
3. Get a value
4. If the value is equal to –1, go to step
7

Exercise _ 8
5. Add to sum ( sum = sum + value)
6. Go to step 3 to get next Value
7. Output the sum
8. Stop

Exercise _ 9
• In Exercise_6, step 3 to 5 will be repeated,
by using for loop .
1. Start ;
2. Count = 6 ;
3. Sum = 0 ;
4. For (n = 1, n <= Count, n + 1)
5. Get number ;
6. Sum = Sum + number ;
7. EndFor

Exercise _ 9
8. Display “ The sum of the numbers
is : “ ;
9. Print Sum ;
10.Stop ;
START
Count=6
Sum = 0
n = 1
IS n <= Count
Print Sum
END
n= n+ 1
Sum = Sum + number
Get number

Exercise _ 10
• Design an algorithm that computes the
absolute difference of two values (X and Y),
where the difference is (X-Y) or (Y-X),
which ever is positive.
1. Start ;
2. Get x ;
3. Get Y ;
4. If ( X > Y )
5. Diff = X – Y;

Exercise _ 10
6. Else
7. Diff = Y - X;
8. EndIf ;
9. Print Diff ;
START
IS
X>Y
Diff= Y-X Diff= X-Y
Read X, Y
END
Print Diff

Exercise _Assignment_2
1. Design an algorithm and the
corresponding flowchart for finding the
sum of the numbers 2, 4, 6, 8, …, n
2. Using flowcharts, write an algorithm to
read 100 numbers and then display the
sum.
3. Write an algorithm to read two numbers
then display the largest.
4. Write an algorithm to read two numbers
then display the smallest.

Exercise _Assignment_2
5. Write an algorithm to read three numbers
6. Write an algorithm to read 100 numbers
7. Design an algorithm and the
corresponding flowchart for finding the
sum of n numbers.

Références
1. ALGORITHMS, FLOWCHARTS, DATA TYPES
AND PSEUDOCODE.
2. Introduction to Flowcharting A Supplement to
Starting Out with C++: From Control Structures to
Objects 5th Edition by Tony Gaddis .
3. http://www.minich.com/education/wyo/styleshee
ts/pseudocode.htm
4. Introduction to Computers Lab Handouts .

Pseudo code.pptx

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