1. Boolean in C++
CSCE 121

2. Boolean Values Logically C++ True False
Represented by an integer in the background
false is 0
true is literal 1 by default
Any non-zero value is truthy

3. Where it is a problem
Some functions that are expected to be Boolean actually return an int.
int isalnum ( int c );
Check if character is alphanumeric (a decimal digit or an uppercase or lowercase letter).
What some students in the past have done
char c = ‘z’;
if (isalnum(c) == true) {
// do something }
Does not always work
Only works for uppercase values

4. Solution Don’t compare Boolean functions with true or false.
Just use the Boolean without comparing it.
What you should do
char c = ‘z’;
if (isalnum(c)) {
// do something }
Always works
isalnum’s return value tells you what kind of char it is:
1: A-Z
2: a-z
4: 0-9