First Program in C with explain:

#include<stdio.h>

          void main()

          {

                   printf("Hello World");

          }

Explain:-

Here,

‘#include<stdio.h>’  -- is known as pre-processor directory.

“#include”  -- is a header folder or directory.

“stdio”       -- is a header file. It has three parts. Which are- stdin, stdout and

                       stderr. stdin is used for input, stdio is used for output and stderr

is used for error.

“.h”             -- is a extension name of the file.

“void main()”-- is a main function, and ‘main’ is the function name.

Without creating a main function, we cannot execute any program.

‘{‘                 -- is indicates the start of the main function.

‘printf’        -- is used for print something to console window.

‘Hello world’  -- is a commend that will be output.

‘;’              -- is known as a terminator, which is used to indicates the end of line.

‘}’                -- is indicates the end of the main function.

If we are declare ‘int main()’ replace of ‘void main()’ though the program is correct. We can just declare a return value at the end of the main function using return keyword, the return value should be an integer because the data type of the function (main) is an integer. If we declare the main function as a char or float then we should declare the return value something like ‘c’ and in case of float it should be ‘6.0’.

Originally the reason is, when the main() function completes execution, it needs to notify the operating system about it’s completion. This is the reason why the last statement in main() is return any value.

          The operating system considers the value that is returned to it to imply that the program has completed execution without any error.