If n is an integer then: if ( n )
means "if n is non-zero"
if ( !n )
means "if n is zero"
When necessary, 0 translates to false, anything non-zero to true.
The construct can also be used for testing the condition of iostreams etc. as well.
Is that what you are asking? Your question (as imbedded in the title of your thread and not in the body of your post) is not clear. Maybe you should post the code leading to your question.