Introduction to Computer

Overview
 Introduction to Computer
 Program and Programming Languages
 Types of Programming Languages
 Low-Level Languages
 Assembly languages
 High-Level Languages
 History of Programming Languages
 Translators
 Compiler
 Interpreter
 Typical C Program Development Environment
 The C Programming Language
 Characteristics of C language
 Basic Program Structure in C Language
1

Introduction
 Computer
A computer is an electronic device which is capable to
• receive the data,
• process the data, and
• provide results
according to a set of instructions
 Program
A program is a set of instructions of a computer language, where each
instruction tells the computer to do something:
For example,
• get two numbers as input,
• add these numbers,
• print the sum as output
2

Programming Languages
 Programming Language
 A programming language defines the rules for writing instructions
 Programmers write instructions in a programming language
 Types of Programming Languages
A number of programming languages are in use today and are
generally categorized as follows:
 Low-Level Languages
 Assembly languages
 High-Level Languages
3

Types of Languages
 Low-Level language or Machine/Binary Language
 This language consists of binary numbers to perform a task
 Machine language is directly understandable to the computer
 Machine languages are machine dependent (i.e., a particular machine
language can be used on only one type of computer)
 Programming in machine-language is very slow, tiresome and error prone
for the programmers
4

Types of Languages
 Assembly language
 It was developed to overcome the problems with machine language
 Assembly language uses English-like abbreviations to programming, such as
ADD for adding numbers
 As the assembly language is not the machine own’s language, so translators
were developed called assemblers
 Assemblers translate the assembly-language programs into the machine
language programs
5

Types of Languages
 High level language
 In early programming languages, the programmers had to write many
instructions to perform a single task
 The high-level languages use a single instruction to perform many tasks
 Compilers or interpreters are used as translators to convert high-level
language programs into machine language
 C, C++, Visual Basic, Visual C++, Visual C#, Python and Java are the most
commonly used high-level programming languages today
6

Types of translators
 Compiler
 Interpreter
7

Translators and Types
 Translator
 A translator is used convert a high level language program
(source code) into machine language (object code)
Source code object code
 Types of translators
 Compiler
 Interpreter
8

Compiler vs. Interpreter
 Compiler
 A compiler first reads the whole source code, and converts
it into a its equivalent machine language, if there are no
errors(bugs)
 Reports a list of errors, if errors in the source code
 Faster translation
 C, C++, C# etc. are the examples of compiled languages
9

Compiler vs. Interpreter
 Interpreter
 An interpreter performs line by line translation
 It first reads the first line of the source code, and converts it into a its
equivalent machine code (if no error), then the second line, and so on
 If there is error, it reports it and the user has to correct it, and after this,
the source code to object code translation occurs
 Slower translation than compiler
 Java, Python etc. are called interpreted languages
10

Why study programming Languages?
 In 1967, Sammet, an American computer scientist and one of the
developers of the COBOL programming language, reported 120
programming languages commonly used
 Today , these languages are many more
 Most programmers never use more than a few, some limit their
career to just on or two
 The goal in learning about a language is its fundamental design
concepts and how this affects its implementation
11

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https://www.tiobe.com/tiobe-index/
Programming Languages Popularity

Programming Domains
 Scientific applications(Fortran)
 Business Applications(COBOL)
 Artificial Intelligence(LISP, Prolog)
 System Programming(C )
 Web software (HTML, PHP, Java)
 General Purpose (Python)
13

14
The Ideal Way to Do Computing
 The ideal way to ask computer to do something is to order it in a
natural language e.g.
 I want to view this webpage
 Calculate my annual tax
 etc.
 However, today’s computer’s are not intelligent enough to
understand our orders in natural language

15
Where We Are in Computers?
 At the very basic level, computers use the concept of an electrical pulse
 Low voltage is represented as 0
 High voltage is represented as 1
 To instruct a computer, we need ask the computer in the language of 0s and
1s commonly known as machine language
 For example, 5 is a number in natural language, so in the language of
0s and 1s, it becomes 101
 In Today’s computing, we use a high-level language to instruct the
computer
 The compiler translates these instructions into the machine language

16
Where are we going?
 The next step in computing is to use natural language over a high-level
language
 But we are many more years away from it
 A lot of research needs to be carried out before we actually see this
 Until then our task is to use high-level languages in its best possible
ways

Program & Its Various Aspects
17

18
What is Programming?
 When we say “programming” we are actually referring
to the science of transforming our intentions in a
high-level programming language

19
Many Aspects of Programming
 Programming is controlling
 computer does exactly what you tell it to do
 Programming is teaching
 computer can only “learn” to do new things if you tell it how
 Programming is problem solving
 always trying to make computer do something useful — i.e., finding
an optimal travel route
 Programming is creative
 must find a good solution out of many possibilities

20
Many Aspects of Programming
 Programming is modelling
 describe salient (relevant) properties and behaviours of a system
of components (objects)
 Programming is abstraction
 identify important features without getting lost in detail
 Programming is concrete
 must provide detailed instructions to complete task

C-Language
 History & characteristics of C language
21

History of C language
 C language was developed by Dennis Ritchie and Ken Thompson in
1972 at Bell Labs where they were working on Unix Operating System
 Dennis Ritchie is known as the founder of the C language
 C was developed to add additional features to its earlier
languages such as B, BCPL, etc.
 It inherits many features of B and BCPL languages
22

Characteristics of C language
1. C is a General Purpose Programming Language
- This means that C language can be used to write a variety of
applications
2. C is a structured programming language
- This means that when you program in C language, a problem is
divided into several small units called functions
3. C is a simple language
- This means that C language is easy to use and has a vast
collection of keywords, operators, built-in functions and data
types
23

4. C is case sensitive language
- This means that in C language the lower case letters are
different from upper case letters
5. C is portable language
-This means that a program written in C language can be run on
different hardware platforms
24

6.C is a flexible language
-This means that C language can be used like a high level
language and like a low level language
7. C is easily available language
-The C software is easy to access and can be easily installed
on a user computer within a few minutes
25

8. C is easily debugged language
 The C is easy to debug
 The C compiler detects syntax errors quickly and easily and
displays the errors along with the line numbers of the code and
the error message
9. C has a number of in-built memory management functions that save
memory and improve the efficiency of the program
10. C has a rich set of library functions for various arithmetic and
trigonometric calculations
26

C-Program Development Environment
(IDE)
27

C IDE
 A C program development environment is called IDE(Integrated
Development Environment)
 Many IDEs available today and some are as follows
 DEVCpp
 Microsoft Visual Studio
 Eclipse
 NetBeans
 Code::Blocks
 etc.
 We use DEVCpp, for C program development in this course
28

C Program Execution Phases
 C program goes through six phases to be executed. These
are as follows:
 Edit
 Preprocess
 Compile
 Link
 Load
 Execute
29

Execution Phases
 Phase 1: Editing/Creating a Program
 Phase 1 consists of editing a file
 To edit a file, we use Dev C++ IDE
 A C program is typed or coded in the IDE
 After coding, the program is stored on a hard disk
 A C program file name should end with the .c extension
 Phases 2 : Preprocessing the Program
 In C language, a preprocessor program is executed automatically
before compilation begins
 Here the C preprocessor calls the preprocessor directives(e.g.
#include<…>)
32

Execution Phases
 Phases 3 : Compiling the Program
 The compiler translates the c program code called source code into
machine language-code called object code
 The compiler translates the C program into machine-language code
 To compile the program, we use the compile command in the IDE
 Phase 4: Linking
 A linker links the object code for the missing functions to produce an
executable image
33

Execution Phases
 Phase 5: Loading
 Before a program can be executed, the program must first be placed in
memory
 This is done by the loader, which takes the executable image from disk
and transfers it to memory
 Additional components from shared libraries that support the program
are also loaded
 Phase 6: Execution
 Finally, the computer, under the control of its CPU, executes the
program one instruction at a time
 To load and execute the program, we run the program in the IDE
34

Basic Program Structure in C
35

Basic Program Structure in C Language
36
#include<stdio.h>
int main()
{
// program statement_1;
// program statement_2
…
return 0;
}

Writing Program in C using DEVCpp IDE
37
Steps to follow:
1. Click on File
2. Select New, and
3. Click on Source File
4. Start coding in the source file(in the figure, sample example)
5. Save it with a name(e.g., first.c)
6. Compile, and
7. Run

Writing Program in C using DEVCpp IDE
38
Sample
Program

C Program Example
#include<stdio.h>
int main()
{
printf("Welcome to C language");
return 0;
}
39
Program output:
Welcome to C language

Example: A simple C Program
#include<stdio.h>
int main()
{
printf("Welcome Studentsn");
Printf(“This is C language statement”);
return 0;
}
40
Program output:
Welcome Students
This is C language statement

Escape sequence
 Escape sequence is a set of characters followed by backslash (),
which has a particular meaning for the compiler to do something
with the output statement
 For example, the escape sequence n means newline, which causes
the cursor to position to the beginning of the next line on the
screen
 C language supports the following escape sequences
42

Escape sequence
43
b for backspace, remove one character at the back
’ single quote, insert a single-quote character in a string

Escape Sequence Example
#include<stdio.h>
int main()
{
printf(“This isn C language statement n”);
printf(“Thist ist Ct languaget statement n”);
printf(“ Thisa isa Ca languagea statement n”);
printf(“ ab n”);
printf(“ This is ”C language” statement n”);
printf(“ ’A’ for Apple n”);
printf(“ Hib n”);
return 0;
}
44

Escape Sequence Example…
45
Program output:
This is
C language statement
This (alert) is (alert) C (alert) language (alert) statement
ab
This is ”C language” statement
‘A’ for Apple
H

Comments
 Comments are used to document a program:
 Improve program readability and help other people read and understand
your program
 Dot cause the computer to perform any action when the program is run
 Ignored by the C compiler and do not cause any machine-language object
code to be generated
 Types of Comments:
 Single-line comments e.g. //This is first C program
 Multi-line comments e.g. /* This is first C program
Author: Ali
Dated: October 20, 2020 */
47

Example: Comments
// A first program in C
/* Author: Ali
Dated: October 05, 2020
*/
#include<stdio.h>
int main()
{
printf(“This is C language statement”);
return 0;
}
48
Program output:

Introduction to Computer

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