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297: Mainline

The evaluation of && and || expressions is complicated by the fact that certain subexpressions may not be evaluated at all.

In && expressions, the left-side operand is evaluated first: If the value of the left-side operand is 0, the right-side operand is ignored completely, and the value of the && expression is 0.

If both operands evaluate to some integer other than 0, the value of the && expression is 1.

In || expressions, the left-side operand also is evaluated first: If the left-side operand evaluates to some integer other than 0, nothing else is done, and the value of the || expression is 1; if both operands evaluate to 0, the value of the || expression is 0.