C Pocket Reference

Relational Operators and Logical Operators

Every comparison is an expression of type int that yields the value 1 or 0. The value 1 means “true” and 0 means “false.” Comparisons use the relational operators listed in Table 1-11.

Table 1-11. The relational operators

Operator	Meaning	Example	Result: 1 (true) or 0 (false)
<	less than	x < y	1 if x is less than y
<=	less than or equal to	x <= y	1 if x is less than or equal to y
>	greater than	x > y	1 if x is greater than y
>=	greater than or equal to	x >= y	1 if x is greater than or equal to y
==	equal to	x == y	1 if x is equal to y
!=	not equal to	x != y	1 if x is not equal to y. In all other cases, the expression yields 0.

The following operands are permissible for all relational operators:

• Two operands with real arithmetic types. The usual arithmetic conversions may be performed on the operands.

• Two pointers to objects of the same type.

The equality operators == and != can also be used to compare complex numbers. Furthermore, the operands may also be pointers to functions of the same type. A pointer may also be compared with NULL or with a pointer to void. For example:

int cmp, *p1, *p2;
. . .
cmp = p1 < p2; // if p1 is less than p2, then cmp = 1; 
               // otherwise cmp = 0.