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Behaviotal Modeling part 4

[ Team LiB ] 7.4 Conditional Statements Conditional statements are used for making decisions based upon certain conditions. These conditions are used to decide whether or not a statement should be executed. Keywords if and else are used for conditional statements. | Team LiB 7.4 Conditional Statements Conditional statements are used for making decisions based upon certain conditions. These conditions are used to decide whether or not a statement should be executed. Keywords if and else are used for conditional statements. There are three types of conditional statements. Usage of conditional statements is shown below. For formal syntax see Appendix D Formal Syntax Definition. Type 1 conditional statement. No else statement. Statement executes or does not execute. if expression true_statement Type 2 conditional statement. One else statement Either true_statement or false_statement is evaluated if expression true_statement else false_statement Type 3 conditional statement. Nested if-else-if. Choice of multiple statements. Only one is executed. if expression1 true_statement1 else if expression2 true_statement2 else if expression3 true_statement3 else default_statement The expression is evaluated. If it is true 1 or a non-zero value the true_statement is executed. However if it is false zero or ambiguous x the false_statement is executed. The expression can contain any operators mentioned in Table 6-1 on page 96. Each true_statement or false_statement can be a single statement or a block of multiple statements. A block must be grouped typically by using keywords begin and end. A single statement need not be grouped. Example 7-18 Conditional Statement Examples Type 1 statements if lock buffer data if enable out in Type 2 statements if number_queued MAX_Q_DEPTH begin data_queue data number_queued number_queued 1 end else display Queue Full. Try again Type 3 statements Execute statements based on ALU control signal. if alu_control 0 y x z else if alu_control 1 y x - z else if alu_control 2 y x z else display Invalid ALU control signal Team LiB Team LiB 7.5 Multiway Branching In type 3 conditional statement in Section 7.4 Conditional Statements there were many alternatives from which one was chosen. The nested if-else-if can become .