如果条件在turbo C ++上

Question

I'm having a problem regarding with if statement in C++ this statement is in do-while loop.

gotoxy(27,22);cout<<"Do you want to continue [Y]?";
    sub=getche();
    if(sub!='y' || sub!='Y')
    {

        gotoxy(27,24);cout<<"INVALID ANSWER!!";
        gotoxy(27,26);cout<<"Closing Program....";
        delay(3000);
        exit(1);
    }else
    {
        sub=ans;
    }
}while(tolower(ans)=='y');

whenever I input y on the variable sub the code on if statement is still executing.. please someone tells me where is the error.. Thanks!

Answer 1

The boolean expression of (sub!='y' || sub!='Y') will always evaluate to true

This line:

if(sub!='y' || sub!='Y')

Needs to be this:

if ( (sub != 'y') && (sub != 'Y') )

Answer 2

Your code if(sub!='y' || sub!='Y') will be true ,no matter what you enter because either sub!='y' or sub!='Y' will evaluate to true. Hence Use && instead of || .