Yes, although the rule for interpretation of integral values as boolean values by C states that 0 is false and any other value is true (a), the results of comparison operators is always 1 or 0.
So the expression (a == b) will never give you 42, for example.
The relevant bits of the standard (C11) are all under 6.5 Expressions:
6.5.8/6: Each of the operators < (less than), > (greater than), <= (less than or equal to), and >= (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is false.
6.5.9/3: The == (equal to) and != (not equal to) operators are analogous to the relational operators except for their lower precedence. Each of the operators yields 1 if the specified relation is true and 0 if it is false.
6.5.13/3: The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it yields 0.
6.5.14/3: The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it yields 0.
That covers all the ones you explicitly mentioned in your question. The only other boolean operation I can think of (off the top of my head) is the logical NOT operator ! which is also covered:
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.
(a): See C11 sections dealing with if, while, do and for, which all contain language along the lines of something happen if/while "the expression compares unequal to zero". Specifically:
6.8.4.1/2: In both forms [of the if statement, one with and one without an else clause], the first substatement is executed if the expression compares unequal to 0. In the else form, the second substatement is executed if the expression compares equal to 0.
6.8.5/4: An iteration statement [while, do and for] causes a statement called the loop body to be executed repeatedly until the controlling expression compares equal to 0.
