In C, two types of names a programmer can use in his program. They are

  • Keywords
  • Identifiers

Keywords - Definition :

Keywords are the pre-defined or reserved names given by the creators of the C language.

Keywords will play a major role during the compilation process. Based on the usage of keywords and identifiers compiler will understand the type of statements that the programmer has written.

As per the ANSI C or C89 standard :

As per the ANSI C or C89 standard, we have 32 keywords. later in C18 or ISO C standard, 12 new keywords are introduced.

12 new keywords added in ISO C or C18 standard:

C is a case-sensitive language. So, Keywords are also case-sensitive i.e AUTO and auto are different.

Below is the C program with few keywords:

#include <stdio.h>
int main()
    printf("Hello world!");
    return 0;