| if, else | Keywords

Keyword Index

Conditional statement.

Keyword `if` is used for conditional execution. The basic form of `if` uses the following syntax:

    if (expression)
       statement1

Alternatively, `if` may be used together with `else`, using the following syntax:

    if (expression)
       statement1
    else
       statement2

If expression is nonzero when evaluated, then statement1 is executed. In the second case, statement2 is executed if the expression is 0.
An optional `else` can follow an `if` statement, but no statements can come between an `if` statement and an `else`. Of course, both statement1 and statement2 may be compound statements (i.e. a sequence of statements enclosed in braces). Here will be given some legal examples:

    if (count < 50) count++;

    if (x < y) z = x;
    else z = y;

    if (x < y)
      {
        printf ("x is smaller");
        return x;
      }
    else
      {
        printf ("x is greater")
        return y;
      }

The #if and #else preprocessor statements look similar to the `if` and `else` statements, but have very different effects. They control which source file lines are compiled and which are ignored.