#include<stdio.h>

int main()
{
	printf("Hello World!");
	return 0;
}

#include<stdio.h>

• The prototypes of different library functions are grouped together into categories according to their functionalities and are stored into different header files.
  stdio.h: prototypes of standard input/output functions
  conio.h: prototypes of console input/output functions
  math.h: Prototypes of mathematics related functions
• Anything starting with '#' will be handled by the preprocessor.
• The 'include' directive causes the entire contents of the file to be inserted into the source code.

int main() {...}

• Function definition:
  

  <return type> <function name> ( <list of arguments> )
  {
  	<function body>
  }

   

printf("Hello World!");

• Prototype:
  

  int printf(const char *format,...);

• Writes the C string to stdout.
• On success, the total number of characters/bytes written is returned. On error, a negative number is returned.