• Every C program follows block structure.
  • It is written as a collection of function also known as sub-routine.
  • The basic structure of a C program is as follow:

[1] Documentation Section:

  • This section contains information about the program such as author name, creation data & time etc.
  • It provides guidelines to the program reader.
  • It may also include logic of the program.
  • This information is written as a comment.

[2] Link Section:

  • It includes different library and header files that are required by the program.
  • These header files are linked with the program during the linking steps.
  • Some standard header files are <stdio.h>,<conio.h>, <string.h> etc.

[3] Definition Section:

  • This section includes all the constant variables.
  • They are defined with the “#define”

C Program Structure[4] Global Declaration Section:

  • All the global variables are defined in this section.
  • Global variables can be accessed by any function of the program.
  • Their scope is entire program.

[5] main() Section:

  • The main()section is the main section of the C- program.
  • Each C- program must have one and only one main function.
  • It is define using main()
  • Every statement of the C- program should be written in the main section.
  • Opening ‘{‘specifies starting of the main function and closing ‘}’ specifies ending of the main function.
  • main section is divided into the following two sections.
    1. Declaration part Executable part
  • Declaration part contains all the local variables to be used in the main section.
  • Executable section contains all the executable statement to perform the task.

[6] Sub-program Section:

  • This section includes all the sub-program definitions.
  • It is used when program is divided into different functions.
  • Its order is not important; it can be place before or after the main section.Normally it is written after the main section.

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