Using true and false in C

Question

As far as I can see there are 3 ways to use booleans in c

1. with the bool type, from then using true and false
2. defining using preprocessor #defin

Answer 1

Whichever of the three you go with, compare your variables against FALSE, or false.

Historically it is a bad idea to compare anything to true (1) in c or c++. Only false is guaranteed to be zero (0). True is any other value.   Many compiler vendors have these definitions somewhere in their headers.  

#define TRUE 1
#define FALSE 0

This has led too many people down the garden path.   Many library functions besides chartype return nonzero values not equal to 1 on success. There is a great deal of legacy code out there with the same behavior.