Question

Write a microprogramming for this operation using one - address, two - address, and three - address? Y = (A * B) -(CD)

I need the answer as soon as possible

Answer 1

One Address Instructions –
This use a implied ACCUMULATOR register for data manipulation.One operand is in accumulator and other is in register or memory location.Implied means that the CPU already know that one operand is in accumulator so there is no need to specify it.

Expression: Y = (A*B)-(CD)
AC is accumulator
M[ ] is any memory location
M[T] is temporary location

LOAD A // AC = M[A]

MUL B // AC = AC * M[B]

STORE T1 // M[T1] = AC

LOAD C // AC = M[C]

MUL D // AC = AC * M[D]

STORE T2 // M[T2] = AC

LOAD T1 // AC = M[T1]

SUB T2 // AC = AC - M[T2]

STORE Y // M[Y] = AC

Two Address Instructions –
This is common in commercial computers.Here two address can be specified in the instruction.Unlike earlier in one address instruction the result was stored in accumulator here result cab be stored at different location rather than just accumulator, but require more number of bit to represent address.

Here destination address can also contain operand.

Expression: Y = (A*B)-(CD)
R1, R2 are registers
M[] is any memory location

MOV R1, A // R1 = M[A]

MUL R1, B // R1 = R1 * M[B]

MOV R2, C // R2 = C

MUL R2, D // R2 = R2 * D

SUB R1, R2 // R1 = R1 - R2

MOV Y, R1 // M[Y] = R1

Three Address Instructions –
This has three address field to specify a register or a memory location. Program created are much short in size but number of bits per instruction increase. These instructions make creation of program much easier but it does not mean that program will run much faster because now instruction only contain more information but each micro operation (changing content of register, loading address in address bus etc.) will be performed in one cycle only.

Expression: Y = (A*B)-(CD)
R1, R2 are registers
M[] is any memory location

MUL R1, A, B // R1 = M[A] * M[B]

MUL R2, C, D // R2 = M[C] * M[D]

SUB Y, R1, R2 // M[Y] = R1 - R2