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IF...END IF Statement Details
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Syntax 1: Block Form
IF condition-1 THEN
[statementblock-1]
[ELSEIF condition-2 THEN
[statementblock-2]] ...
[ELSE
[statementblock-n]]
END IF
Syntax 2: Single-Line Form
IF condition THEN statements [ELSE statements]
Usage Notes
■ Use the object form of the IF statement to set up processing tasks
specific to a particular control type. See: ◄IF TYPEOF Statement►
■ The single-line form of the IF statement is best for short,
straightforward tests where only one action is taken.
■ The block form of this statement provides several advantages:
• Adds structure and flexibility by allowing conditional branches across
several lines
• Tests more complex conditions
• Allows you to use longer statements and structures
• Allows program structure to be guided by logic rather than by the
number of statements that fit on a line
• Makes programs easier to read, maintain, and debug
■ In executing a block-form IF, Visual Basic tests the first Boolean
expression (condition-1):
• If the Boolean expression is True (nonzero), the statements following
THEN are executed.
• If the first Boolean expression is False (zero), Visual Basic begins
evaluating each ELSEIF condition in turn.
■ When Visual Basic finds a true condition, the statements following the
associated THEN are executed. If none of the ELSEIF conditions is true,
the statements following the ELSE are executed. After the statements
following a THEN or ELSE are executed, the program continues with the
statement following the END IF.
■ The ELSE and ELSEIF blocks are optional. You can have as many ELSEIF
clauses as you want in a block IF. Any of the statement blocks can
contain nested block IF statements.
■ Visual Basic looks at what appears after the THEN keyword to determine
whether an IF statement is a block IF. If anything besides a comment
appears after THEN, the statement is treated as a single-line IF
statement.
■ A block IF statement must be the first statement on a line. The ELSE,
ELSEIF, and END IF parts of the statement can have only a line number
or line label in front of them. The block must end with an END IF
statement.
■ Statement blocks can include GOTO linenumber or GOTO linelabel
directives. Note: GOTO is optional with a line number, but is required
with a line label.
■ The single-line form is never required. Any program using single-line
IF...END IF statements can be written using block form.
■ You can have multiple statements with a single condition, but the
statements must be on the same line and separated by colons:
IF A > 10 THEN A = A + 1: B = B + A: LOCATE 10,22: PRINT B,A