Test: Arithmetic Logic Units - Electronics and Communication Engineering (ECE) MCQ

The basic building blocks of the arithmetic unit in digital computers are adders. Since a parallel adder is constructed with a number of full-adder circuits connected in cascade. By controlling the data inputs to the parallel adder, it is possible to obtain different types of arithmetic operations.

In a combinational circuit, the output at any time depends only on the input values at that time and not on past or intermediate values.

Combinational circuits are the ones which do not depend on previous inputs and depends only on the present values. The given arrangement A, B, E, C, D is the right sequence for the designing of the combinational circuits.

The design of an ALU is based on combinational logic. Because the unit has a regular pattern, it can be broken into identical stages connected in cascade through carries.

If the two numbers include a sign bit in the highest order position, the bit conditions of interest are the sign of the result, a zero indication and an overflow condition.

In an ALU, status bit conditions are sometimes called condition code bits or flag bits. It is so called because they tend to represent the status of the respect flags after any operation.

If the two numbers are unsigned, the bit conditions of interest are the output carry and a possible zero result.

Since the logic gates NOR and NAND are known as universal logic gates, therefore it can be used to design all the three basic gates AND, OR and NOT. Thus, it means that any operations can be obtained by implementation of these gates.

In a sequential circuit, the output at any time depends on the present input values as well as past output values. It also depends on clock pulses depending on whether it’s synchronous or asynchronous sequential circuits.

A digital system consists of two types of circuits and these are a combinational and sequential logic circuit. Combinational circuits are the ones which do not depend on previous inputs while Sequential circuits depend on past inputs.