tolower()

turns a given char[] representation of a string into the lowercase version of itself. e.g. AYsndaU → aysndau

#include <stdio.h>
 
char lower(char c){
    if (c >= 'A' && c <= 'Z'){
        return (c + 'a' - 'A');
    }
    else return c;
 
}
 
int main(){
    char thechar;
 
    for (thechar = 'A' ; thechar <= 'Z' ; thechar++){
		printf( "%c", lower(thechar));
    }   
    return 0;
}