C Program to Convert lowercase letters to uppercase

/*Convert lowercase letters to uppercase*/
#include<stdio.h>
#include<string.h>

void main() {
    char phr[50];
    int i;
    clrscr();
    printf("\nEnter the phrase in small letter:\n");
    gets(phr);
    for (i = 0; i < 50; i++)
        phr[i] = toupper(phr[i]);
    puts(phr);
}