Overview of C programming

1. Overview of C language

2. History
 C is a structured programming language developed by
Dennis Ritchie in 1973 at Bell Laboratories.
 C programming language features were derived from
an earlier language called “B”.
 C language was invented for implementing UNIX
operating system.
 Today's most popular Linux OS and RBDMS MySQL
have been written in C.

4. Features
 Simple
 Portable
 Structured programming language
 Rich library
 Memory Management
 Speed
 Pointer
 Recursion
 Middle level language

5. Basic Structure of ‘C’

6. Basic Structure of ‘C’ (Cont.)
 Documentation Section :-
 It has set of comment lines(name of program, author
details).
 Non-executable statement.
 Can’t be nested.
 eg. /* Program to find factorial of a number
By: Smith */
/* Welcome /* friends */ ! */ Illegal

7. Basic Structure of ‘C’ (Cont.)
 Link Section :-
 It provides instructions to the compiler to link function
from the system library.
 # include Directive:- It tells the preprocessor to insert
the contents of another file into the source code at the
point where the #include directive is found.
 stdio– Standard Input /Output
 conio– Console input/Output
 math- contains mathematical functions like(cos(), sin(),
sqrt(), abs())
 Eg. #include<stdio.h>

8. Basic Structure of ‘C’ (Cont.)
 Definition Section :-
 It defines all symbolic constants.
 eg. #define PI 3.14
 It’s not a statement. Therefore it should not end with a
semicolon.
 Generally written in uppercase.

9. Basic Structure of ‘C’ (Cont.)
 Global Declaration Section :-
 Two types of declarations:
1.) Local variable declaration
2.) Global variable declaration
 Global variables are declared out side the main
function. Scope of variable is whole program.
 Local variables are declared inside the main function.
Scope of variable is the function in which it is declared.

10. Basic Structure of ‘C’ (Cont.)
 main() function Section :-
 Every C program must have one main function section.
 Two parts,
1) Declaration part: It declares all the variables used in
the executable part.
2) Executable part: It contains instructions to perform
certain task.

11. Basic Structure of ‘C’ (Cont.)
 Subprogram Section :-
 It contains body of user defined function.
 Eg. int sum (int a, int b)
{
int c;
c=a+b;
return c;
}

12. Example 1
 /*Documentation Section: Program to find the area of
circle*/
#include <stdio.h> /*link section*/
#include <conio.h>/*link section*/
#define PI 3.14 /*definition section*/
float area; /*global declaration section*/
void main()
{
float r; /*declaration part*/
printf("Enter the radius of the circlen"); /*executable
part starts here*/

13. Example 1(Cont.)
scanf("%f",&r);
area=PI*r*r;
printf("Area of the circle=%f",area);
getch();
}

14. Basic Syntax

15. Tokens
 A token is either a keyword, an identifier, a constant, a
string literal, or a symbol.
 Eg. printf("Hello, World! n");
 The individual tokens are:
printf
(
"Hello, World! n"
)
;

16. Semicolons(;)
 It is a statement terminator.
 Each individual statement must be ended with a
semicolon.
 It indicates the end of one logical entity.
 Eg.
printf("Hello, World! n");
return 0;
or
printf("Hello, World! n"); return 0;

17. Comments
 Comments are like helping text in your C program and
they are ignored by the compiler.
 Single line comment: //first program in c
 Multiline comment: /* first
program
in
C */

18. Identifiers
 A C identifier is a name used to identify a variable,
function, or any other user-defined item.
 An identifier starts with a letter A to Z or a to z or an
underscore _ followed by zero or more letters,
underscores, and digits (0 to 9).
 C does not allow punctuation characters such as @, $,
and % within identifiers.
 C is a case sensitive programming language.
 Eg. int money;
 Here, money is identifier.

19. Identifiers(Cont.)
 Acceptable identifiers:
 mohan zara abc
 move_name a_123 myname50
 _temp j a23b9
 retVal

20. Keywords
 They are reserved words in C.
 These reserved words may not be used as constant or
variable or any other identifier names.
 Eg. int money;
 Here, int is keyword.

22. Whitespace
 Whitespace describes blanks, tabs(t), newline(n)
characters.
 Whitespace separates one part of a statement from
another and enables the compiler to identify where one
element in a statement, such as int, ends and the next
element begins.
 Eg. int age;

23. Q & A
 abc@12
 xyz!
 Smith
 S09
 A_b
 $abc
 12ab
 float
 break