Question

Condition expression such as those involving && and ||, do they always evaluate to 0 or 1? Or for true condition, numbers other than 1 are possible? I am asking because I want to assign a variable like this.

int a = cond1 && cond2;

I was wondering if I should do the following instead.

int a = (cond1 && cond2)? 1:0;

Answer 1

The logical operators (&&, ||, and !) all evaluate to either 1 or 0.

C99 §6.5.13/3:

The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it yields 0. The result has type int.

C99 §6.5.14/3:

The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it yields 0. The result has type int.

C99 6.5.3.3/5:

The result of the logical negation operator ! is 0 if the value of its operand compares unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int.
The expression !E is equivalent to (0==E).