Name of function is case sensitive in c programming

C programming language is case sensitive. Function is not exception of this. 

Example:

#include<stdio.h>

int main(){

   CQUESTIONBANK();

   return 0;

}

int cquestionbank(){

   printf("BLOCK 1");

   return 0;

}

int CQUESTIONBANK(){

   printf("BLOCK 2");

   return 1;

}

Output: BLOCK 2

Definition of function in c
Name of function includes only alphabets, digit and underscore.
First character of name of any function must be an alphabet or underscore.
Name of function cannot be any keyword of c program.
Name of function cannot be global identifier.
Name of function cannot be exactly same as of name of function in the same scope.
Name of function is case sensitive
Name of function cannot be register Pseudo variable

Function tutorial 

C tutorial