So far, we have covered two important concepts called variables and their data types. We discussed how to use int, long, and float to specify different data types. We also learnt how to name the variables to store different values.

Though this chapter is not required separately because reserved keywords are a part of basic programming syntax, we kept it separate to explain it right after data types and variables to make it easy to understand.

Like int, long, and float, there are many other keywords supported by C programming language which we will use for different purpose. Different programming languages provide different set of reserved keywords, but there is one important & common rule in all the programming languages that we cannot use a reserved keyword to name our variables, which means we cannot name our variable like int or float rather these keywords can only be used to specify a variable data type.

For example, if you will try to use any reserved keyword for the purpose of variable name, then you will get a syntax error.

#include <stdio.h>

int main() {
   int float;
   float = 10;
   
   printf( "Value of float = %dn", float);
}

main.c: In function ''main'':
main.c:5:8: error: two or more data types in declaration specifiers
   int float;
......

#include <stdio.h>

int main() {
   int count;
   count = 10;

   printf( "Value of count = %dn", count);
}