Write a program that reads a string of characters STR and converts all uppercase letters to lowercase and vice versa.

The result will be stored in the same STR variable and displayed after the conversion.

#include <stdio.h>
#define size 100
int main()
{
    char str[size];  
    int I;         

    printf("The the string to convert : ");
    gets(str);

    for (I=0; str[I]; I++)
    {
        if (str[I]>='A' && str[I]<='Z')
                 str[I] = str[I]-'A'+'a';
        else if (str[I]>='a' && str[I]<='z')
                 str[I] = str[I]-'a'+'A';
    }

    printf("Converted string : %s\n", str);
    return 0;
}