C program to convert the lower case characters of a string into upper case

#include <stdio.h>
#include <conio.h>
int main()
{
char str[100], upper_str[100];
int i=0;
clrscr();
printf("\n Enter the string :");
gets(str);
while(str[i] != '\0')
{
if(str[i]>='a' && str[i]<='z')
upper_str[i] = str[i] – 32;
 else
upper_str[i] = str[i];
 i++;
}
upper_str[i] = '\0';
printf("\n The string converted into upper case is : ");
puts(upper_str);
return 0;
}