toupper() is a function designed to convert lowercase words/characters into upper case.
//Example
#include<stdio.h>
#include<ctype.h>
int main()
{
char c;
c=a;
printf("%c after conversions %c", c, toupper(c));
c=B;
printf("%c after conversions %c", c, toupper(c));
//Output:
a after conversions A
B after conversions B
