### 19.2 `if` Statement ¶

An `if` statement computes an expression to decide whether to execute the following statement or not. It looks like this:

    if (condition)
      execute-if-true

The first thing this does is compute the value of condition. If that is true (nonzero), then it executes the statement execute-if-true. If the value of condition is false (zero), it doesn’t execute execute-if-true; instead, it does nothing.

This is a complex statement because it contains a component execute-if-true that is a nested statement. It must be one and only one statement. The way to put multiple statements there is to group them into a block (see Blocks).