Conitional execution of instructions. If the condition is fulfilled, then the instructions between THEN and ENDIF or THEN and ELSE are executed.
In the second form the instructions between ELSE and ENDIF are executed, if the condition is not fulfilled.

A condition is any boolean (logical) expression.

Example:

IF a>b THEN ? "A is greater than B" ELSE ? "A is smaller or equal to B" ENDIF IF a % 2=0 THEN PRINT "A is even": ENDIF

In the form IF <instruction> GOTO <label> with fulfilled condition a jump to the label is executed. This is a short form for the instructions:

IF <condition> THEN GOTO <label>: ENDIF