C Program to Convert Uppercase String to Lower Case

/* C program to convert uppercase string to lower case */
#include<stdio.h>
#include<string.h>

int main(){
   /* This array can hold a string of upto 25
    * chars, if you are going to enter larger string
    * then increase the array size accordingly
    */
   char str[25];
   int i;
   printf("Enter The String: ");
   scanf("%s",str);
 
   for(i=0;i<=strlen(str);i++){
      if(str[i]>=65&&str[i]<=90)
         str[i]=str[i]+32;
   }
   printf("\nLower Case String is: %s",str);
   return 0;
}

Enter The String: TUTORIALSRACK

Lower Case String is: tutorialsrack
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Process exited after 5.957 seconds with return value 0
Press any key to continue . . .