### 19.3 `if-else` Statement ¶

An `if`-`else` statement computes an expression to decide which of two nested statements to execute. It looks like this:

    if (condition)
      if-true-substatement
    else
      if-false-substatement

The first thing this does is compute the value of condition. If that is true (nonzero), then it executes the statement if-true-substatement. If the value of condition is false (zero), then it executes the statement if-false-substatement instead.

This is a complex statement because it contains components if-true-substatement and if-else-substatement that are nested statements. Each must be one and only one statement. The way to put multiple statements in such a component is to group them into a block (see Blocks).