The sequential constructs refer to the VHDL language constructs that execute in sequence. The different sequential constructs are : Wait statement If statement Case statement Loop statement Null statement Next statement Assertion statement Report statement Procedure call statement Return statement we now discuss all these sequential statements in the  following paragraph : IF statement: The IF statement used to transfer the control of the program to another set of sequential statement based on the value of the condition in the expression that evaluates to BOOLEAN value. The syntax of the IF statement is: Format-1 Format-2 Format-3 IF expression then Statement(s); ELSE Statement(s) END IF IF expression then Statement(s); ELSIF expression then Statement(s) -- END IF IF expression then IF expression then IF expression then Statement(s); ELSE Statement(s) End if; End if; End if; The following example illustrates the use of if