Introduction to C
Programming
Introduction
Books
1)The C Programming Language by Brian W.
Kernighan and Dennis M. Ritchie, PHI.
2) Programming in C by E. Balguruswamy, Tata
Mcgraw Hill Publishing.
What is C?
C
A language written by Brian Kernighan
and Dennis Ritchie. This was to be the
language that UNIX was written in to
become the first "portable" language
In recent years C has been used as a general-
purpose language because of its popularity with
programmers.
History
In 1972 Dennis Ritchie at Bell Labs writes C and in
1978 the publication of The C Programming Language
by Kernighan & Ritchie caused a revolution in the
computing world
In 1983, the American National Standards Institute
(ANSI) established a committee to provide a modern,
comprehensive definition of C. The resulting definition,
the ANSI standard, or "ANSI C", was completed late
1988.
Why C Still Useful?
C provides:
Efficiency, high performance and high quality s/ws
flexibility and power
Provide functionality through rich set of function libraries
Gateway for other professional languages like C → C++ → Java
C is used:
System software Compilers, Editors, embedded systems
data compression, graphics and computational geometry, utility
programs
Also used in application programs
Development with C
Four stages
▪ Editing: Writing the source code by using some IDE or editor
▪ Preprocessing or libraries: Already available routines
▪ compiling: translates or converts source to object code for a specific
platform source code -> object code
▪ linking: resolves external references and produces the executable
module
Note! Program correctness and robustness are most important
than program efficiency
Programming languages
Various programming languages
Some understandable directly by computers
Others require “translation” steps
– Machine language
• Natural language of a particular computer
• Consists of strings of numbers(1s, 0s)
• Instruct computer to perform elementary
operations one at a time
• Machine dependant
Programming languages
Assembly Language
– English like abbreviations
– Translators programs called “Assemblers” to convert
assembly language programs to machine language.
– E.g. add overtime to base pay and store result in gross
pay
LOAD BASEPAY
ADD OVERPAY
STORE GROSSPAY
Programming languages
High-level languages
– To speed up programming even further
– Single statements for accomplishing substantial tasks
– Translator programs called “Compilers” to convert
high-level programs into machine language
– E.g. add overtime to base pay and store result in
gross pay
grossPay = basePay + overtimePay
History of C
History of C
Evolved from two previous languages
– BCPL , B
BCPL (Basic Combined Programming Language) used
for writing OS & compilers
B used for creating early versions of UNIX OS
Both were “typeless” languages
C language evolved from B (Dennis Ritchie – Bell labs)
** Typeless – no datatypes. Every data item occupied 1 word in memory.
History of C
Hardware independent
Programs portable to most computers
Dialects of C
– Common C
– ANSI C
• Called American National Standards Institute ANSI C
Case-sensitive
Structure of C Language program
1 ) Comment line
2) Preprocessor directive
3 ) Global variable declaration
4) main function( )
{
Local variables;
Statements;
User defined function
}
}
Simple C Program
/* A first C Program*/
#include<stdio.h>
int main (void)
{
printf (“Welcome to C Programming language.\n");
return 0;
}
Output: welcome to c programming language.
Comment line
It indicates the purpose of the program.
It is represented as
/*……………………………..*/
Comment line is used for increasing the readability of the
program.
It is useful in explaining the program and generally used for
documentation.
Preprocessor Directive:
#include tells the compiler to include information about the
standard input/output library.
It is also used in symbolic constant such as
#define PI 3.14(value).
The stdio.h (standard input output header file) contains
definition & declaration of system defined function such as
printf( ), scanf( ) etc.
Generally printf() function used to display and scanf()
function used to read value
Global Declaration:
This is the section where variable are declared globally so
that it can be access by all the functions used in the
program.
And it is generally declared outside the function :
main()
It is the user defined function and every function has one
main() function from where actually program is started and
it is encloses within the pair of curly braces.
The main( ) function can be anywhere in the program but in
general practice it is placed in the first position.
The main( ) function return value when it declared by data
type as
int main( )
{
return 0 ;
}
The main function does not return any value when it has void
(means null/empty) as
void main()
{
printf (“C language”);
}
Output: C language
