Practical C Programming, 3rd Edition

The ? and : operators work much the same as if/then/else . Unlike if / then/else , the ?: operators can be used inside of an expression. The general form of ?: is:

( expression ) ? expr1 : expr2 ;

For example, the following assigns to amount_owed the value of the balance or zero, depending on the amount of the balance:

amount_owed = (balance < 0) ? 0 : balance;

The following macro returns the minimum of its two arguments:

#define min(x, y) ((x) < (y) ? (x) : (y))