Convert All Uppercase to Lowercase & Vice Versa in a String

 

#include<stdio.h>
#include<string.h>
int main()
{
    char str[100];
    int len,i;
    printf("Enter a String: ");
    fgets (str,100,stdin);
    len= strlen(str)-1;

    for(i = 0; i<len; i++)
    {
        if(isupper(str[i]))
        {
            str[i]=tolower(str[i]);
        }
        else if(islower(str[i]))
        {
            str[i]=toupper(str[i]);
        }
    }
    printf("The Converted Text is :  %s",str);
    return 0;
}