01  #include<stdio.h>
02  #include<string.h>
03  
04  int main()
05  {
06   
07   char str[20] = "happy birthday";
08   printf("Original string is: %sn", str);
09   strupr(str);
10   printf("String after strupr: %sn", str);
11   return 0;
12   
13  }

 OUTPUT :
 
 Original string is: happy birthday
 
 String after strupr: HAPPY BIRTHDAY