How to invoke toupper and tolower function?

Question

How can I invoke toupper and tolower function?
I coded like this ->
int main() {
char string[100];
cin>>string ;
for (int i=0;string[i]!='\0';i++)
{if(isupper(string[i])!=0)
{putchar tolower(string[i]);}
if(islower(string[i])!=0)
{putchar toupper(string[i]);}
}
cout<<"\n"<<string;
return 0;
}

Answer 1

You didn't write braces when calling putchar(), which is of course a function, in both if-statements. Fixing that makes the code run:
https://code.sololearn.com/czSzCvtL7fd3/?ref=app

Answer 2

you have to put else before second if statement to be checked at loop in my understanding