Basic Structure of C programs

Structure of C programs

A C program is separated into six main sections. i.e.

1)        Documentation section

2)        Link section

3)        Definition section

4)        Global Declarations section

5)        Main functions section

6)        Subprograms section

 

1)  Documentation section:

·        It uses comment lines for detail of program such as name of program, author and date of program.

·        There are two way to give comments i.e. single line comment and multi line comments.

·        Single line comment is starts with special character i.e.  //  (double slash)

·        multi line comments is starts with special character i.e.  /*  ( slash and asterisk) and end with */ (asterisk and slash)

2)  Link section:

·        Link section supplies instructions to the compiler to link function from the system library.

·         In link section pre-processor directive  #include<File name>

Where, file name is different header file

Ø  #include<stdio.h>  (Standard input-output header)

It is used to perform input and output operations using functions scanf() and

printf().

Ø  #include<conio.h> (Console input-output header)

It is used to perform console input and console output operations like clrscr() to clear the screen and getch() to get the character from the keyboard.

Ø  #include<math.h> (Math header )

It is used to perform mathematical operations like sqrt() - obtain the square root and pow() - the power of a number respectively.

3)  Definition section:

·        It is define all symbolic constants with using pre-processor #define

Ø   Example -   #define PI 3.14

Ø   Symbolic constant are written in capital letter.

4)  Global declaration section:

·        The variable used in more than one functions that variable is called global variable.

·        These global variable declared outside of all functions called as global declaration section

5)  Main() Function section:

 

·        Any C program must have one main() function.

·        main() function start with  {   i.e. left brace and end with  }  i.e. right brace.

·        main() function section contain two parts, i.e. Declaration part and Execution part.

o   Declaration part – declared all variables used in execution part.

o   Execution part – minimum one statement written in this section.

·        All statements written in main() ends with ; (semicolon)

·        The compiler starts execution from the main() function.

·        The return type of the main() function can be void also not necessarily int.

6)  Subprogram section:

·        It contains all user define functions.

·        All user define functions are called in main() function.

·        Subprogram section place after main function