Chapter 1 (Solid Mechanics).ppt

INTRODUCTION TO
COMPUTER
PROGRAMS
1
Chapter

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INTRODUCTION C++ PROGRAMMING
© Oxford Fajar Sdn. Bhd. (008974-T), 2015 1– 3
At the end of this chapter, you should be able to:
Understand the concepts and importance of programs
and programming.
Differentiate between program, compiler, interpreter and
assembler.
Apply the steps in the program development life cycle.
Learning Outcomes

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Introduction
 Computers can be found anywhere from the size of a
desktop to smaller than the palm of one’s hand such as
desktop computers, notebooks, netbooks, tablet PCs
and mobile devices.
 Many kinds of applications or apps can be downloaded
into the tablet or smartphone.

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Introduction (cont.)
 There are many ways to develop these applications.
– Some websites provide templates to create apps
quickly
– Users with programming knowledge can create their
apps from scratch.
 Examples of systems/apps developed using
programming language:
– Automated Teller Machine (ATM) systems,
– Student Information Systems
– Online Ticketing Systems

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Overview of Computers
and History of
Programming Language
19th
Century
• first general purpose computing device.
20th
Century
• early analogue computers have been invented.
1936
• first freely programmable computers were developed.
1940s
• electronic programmable computers using vacuum tubes and transistors have
been created.
1950-1960s
• commercial computers, computer games and programming languages were
developed.
1975
• mainframes and supercomputers were available.
1981
• IBM introduced its personal computers
1983
• The first personal computer with a graphical user interface was introduced
H
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S
T
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O
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P
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Basic Operation of a Computer
 A computer is a device that can process data.
 Data consists of raw facts or unprocessed information.
• Input – accepts data from user
• Process – manipulate data
• Output – produce result
• Storage – store result
Basic operation of a computer

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Computer Components
 Computers are electronic devices capable of performing
computations and making logical decisions at speeds
faster than human beings.
Hardware Software
Computer Component

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Language of a Computer
 Computers can only understand machine language.
 Machine language is also called binary numbers or
binary code, which is a sequence of 0s and 1s.
 The digits 0 and 1 are called binary digits or bits.
 A sequence of 8 bits is called a byte.

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 machine dependent
 language is
mnemonic
 use assembler as
translator to
translate to machine
language
 machine independent
 the instructions are quite
English-like
 use compiler/interpreter as
translator to translate to
machine language
 Example: JAVA, C++, COBOL
Types of Programming Language

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Types of Programming Language
(cont.)
 Example:
To calculate the BMI of a user given the formula:
height(m)
x
(m)
height
(kg)
weight
BMI 

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Differences Between
Programs and Programming
 A program is a set of instructions that tell the computer how to
solve a problem or perform a task.
 Programming is the process of designing and writing computer
programs.
 A program is like a recipe. It contains a list of ingredients (variables)
and a list of directions (statements) that tell the computer what to do
with the variables.
 A program can be as short as one line of code, or as long as several
million lines of code.
 Computer programs guide the computer through orderly sets of
actions specified by the computer programmers.
 The programmer must decide what the programs need to do,
develop the logic of how to do it and write instructions for the
computer in a programming language that the computer can
translate into its own language and execute.

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The Importance of Computer
Programming
 Able to perform difficult tasks without making human-type errors
such as lack of focus, energy, attention or memory.
 Capable of performing extended tasks at greater serial speeds than
conscious human thoughts.
 Human brain cannot be duplicated or ‘re-booted’ like computers,
and has already achieved ‘optimization’ through design by
evolution, making it difficult to upgrade.
 Human brain does not physically integrate well, externally or
internally with current hardware and software.
 Non-existence of boredom in computers when performing repetitive
tasks allows jobs to be done faster and more efficiently.

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The Importance of Writing a Good
Program
Names for variables, types and functions
 Variables and constants are storage locations in the computer’s
memory that match with associated names known as identifiers.
 The following are some standards that can be used when naming
variables, constants, types and functions:
1. Function names will start with a lowercase letter.
Example: double calculateBMI (double, double);
2. Variable names start with a lowercase letter and the length must
not be more than 40 characters.
Example: double weight, height;
3. Constant names can be all in capital letters.
Example: const int MAX_SIZE =10;

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Program (cont.)
Indentation styles and spacing
In order to improve readability in programming, indentation can be
used to format the program source code.
• A text editor is used to create a program by following the rules or
syntax of different programming languages.
Spaces can also be added in between sentences to make programs
much more readable.
A new level of indentation should be used at every level of statement
nesting in the program.
The minimum number of spaces at each indentation should be at
least three.
• Many programmers use a tab mark (typically 8 spaces) which will be
easier when indenting source code.

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Program (cont.)

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C++ Relationship Between
Programs, Compiler, Interpreter and
Assembler

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C++ Program Structure

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C++ Program Structure (cont.)

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The Flow of Program Execution

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Comments
 Important in any program as they are very useful for documentation but it is
not compulsory to write comments in programs.
– Comments are not source code, thus they will not be read by the
compiler.
 Can be written in any way, according to the programmers’ preferences
 Explain the purpose, parts of the program and keep notes regarding
changes to the source code
 Store programmers’ name for future reference.

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Pre-processor Directive
 Also known as a header file in C++.
 It is a line of code that begins with the # symbol.
 Header files are not executable code lines but instructions to the
compiler.
 Header files are usually included at the top of the program before
the main function.
 The most common and important header file is
#include<iostream>.
– This header file tells the pre-processor to include the contents of
the file <iostream> which are the input and output operations
(such as printing to the screen).

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Function
 Main Function
– Every C++ program contains one or more functions,
but one of it must be named as main .
– A function is a block of code that carries out specific
tasks.
– Generally, a main function starts with the function
type void or int before it is followed by the word
main and a pair of parentheses ().
– It is more advisable to write the function type int in
the main function but the word return 0 must be
written at the end of the function before it is closed.

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 Braces
– Body of the main function which is enclosed in braces
{}.
• Used to mark the beginning and end of blocks of
code in any program.
• The open brace { is placed at the beginning of
code after the main function and the close brace }
is used to show the closing of code.
• The code after the } will not be read/evaluated by
the compiler.
Function (cont.)

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Function (cont.)
 Statement
– A function consists of a sequence of statements that
perform the work of the function.
– Every statement in C++
ends with a semicolon (;).

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Program Development
Life Cycle
 The process of developing a program is called program
development.
 The process associated with creating successful
application programs is called the Program
Development Life Cycle (PDLC).
Analysis Design
Implementatio
n/Coding
Testing/
Debugging Maintenance

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Analysis
 First step in the Program Development Life Cycle
(PDLC).
 This process is done by reviewing the program
specifications.
 Other criteria must also be identified, especially the data
that will be used as input, the process involved and the
output that will be produced.

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Design
 A programmer needs to develop a series of steps with
logical order, which when applied would produce the
output of the problem.
 A solution is created using a structured programming
technique known as algorithm, which consists of
pseudocode and flowchart.
– A procedure or formula for solving a problem.
– A step-by-step problem solving process where the
result is attained in a limited amount of time.

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Design (cont.)
 Some requirements must be satisfied when creating an
algorithm:
1. Unambiguousness
2. Generality
3. Correctness
4. Finiteness

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 Before an algorithm is created, the three types of control
structure should be understood first.
 A control structure is a pattern to control the flow of a
program module.
Design (cont.)

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Pseudocode
 A semiformal, English-like language with a limited
vocabulary used to design and describe algorithms.
 Every statement in pseudocode involves keywords
which define the process and operands.
 Each pseudocode statement should be written in a
separate line.

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Flow Chart
 A graphic presentation of the detailed logical sequence
of steps needed to solve programming problems.
 Uses geometric symbols where different symbols are
used to represent different actions such as start/stop,
decision, input/output, processing and looping.
 Similar to pseudocode, keywords are written in
uppercase, while variable and constant names as well
as operations for the statements are written in lower
case.

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Implementation/Coding
 The pseudocode and flow chart which have been done
in the design step will be converted into a program by
using certain programming languages such as BASIC,
JAVA, C or C++.
 This step solves the problem by enabling the user to
start writing the programs.

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 Coding is the actual process of creating a program in a
programming language.
 The coded program is referred to as source code.
– Must follow certain rules which are called syntax.
– Must then be saved as a program which has the
extension ‘.cpp’.
 To be executed, the program is converted by the
computer into object code using a special program or
translator such as a compiler or interpreter.
Implementation/Coding (cont.)

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Testing/Debugging
 The step for checking and verifying the correctness of
the program.
 The process of making sure a program is free of errors
or ‘bugs’ is called debugging.
 Preliminary debugging begins after the program has
been entered into the computer system.

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Maintenance
 Last step in the Program Development Life Cycle
(PDLC).
 Essentially, every program, if it is to last a long time,
requires ongoing maintenance.
 A process of updating software for any changes,
corrections, additions, moving to a different computing
platform and others so that it continues to be useful.
 A costly process.
 Can be very useful especially on extending the life of a
program.

Chapter 1 (Solid Mechanics).ppt

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