7/27/2019 COA Assign 1 Feb 11

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Computer Organization and Architecture

3rd semester, E&C engineering dept.

First and second assignment

1. Write short notes on the history of computers stating the key concepts that were

developed in all the generations.

2. Explain stack based computing machine using a neat block diagram showing the basic

structure. List example instructions for the above machine. Explain how it can be used

for computing the following expression, )/)((*)( EDCBAY += showing the stack

contents while it is getting executed.

Note: The instruction sequence Push A, Push B and Div will push the resulting

value of the operation B/A onto the stack. The instruction sequence Push A, Push B and

Sub will push the resulting value of the operation B-A onto the stack.

3. Write 3-address, 2-address, 1-address and 0-address machine instructions for evaluating

the following expressions. Assume that the instructions support memory operandswherever applicable.

a. ))/((*)( HFGEDCBAY +++=

b. )/)/(()(* ONMLKJIZ ++=

Note: The instruction sequence Push A, Push B and Div will push the resulting

value of the operation B/A onto the stack. The instruction sequence Push A, Push B and

Sub will push the resulting value of the operation B-A onto the stack.

4. Write 3-address and 2-address instructions for the given expression having a restriction

that the destination operand must be a register. Write another version for the same

without using any registers. Compare all the 4 sequence of instructions with respect to

the following parameters.a. Number of instructions b. program size ( bytes )

c. Number of distinct registers d. number of memory accesses for operands))/(*/()( GFEDCBAY ++=

Assume that the memory address is of 16 bits, register address is of 3 bits and

opcode is of 8 bits in length. Write your comments for the comparative analysis.

5. Encode the following instructions using Huffman encoding technique, given are the

instructions and their frequency of usage. Find the average number of bits needed for

instruction encoding.

Instruction Frequency of usage

MOV 0.14

CALL 0.13

RET 0.13

ADD 0.09

AND 0.07

CMP 0.06

JMP 0.02

MUL 0.09

DIV 0.04SUB 0.03

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7/27/2019 COA Assign 1 Feb 11

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SHR 0.04

SAR 0.06

SAL 0.01

JNZ 0.08

HLT 0.01

6. In a computer instruction format, there are 12 bits for coding the instructions supported

by the processor. If 4 bits are used for specifying the address, then give a design using

expanding opcode technique which will support the following requirements. Twelve 2-

address instructions, thirty two 1-address instructions and four 0-address instructions.

7. Explain with a neat diagram and flowchart a 16 by 16 barrel shifter.

8. Write appropriate instructions for the following operations. Assume register length as 8

bits.

a. Clearing bits B7, B3 and B0 of register R0.b. Setting bits B6, B2 and B1 of register R1.

c. Complementing all the 8 bits of register R2.

d. Complementing MSB and LSB of register R3.

9. Represent the following numbers in 2s complement using 4 bits and perform the

following operations. Indicate carry, overflow, sign and zero flag bits for every

operation.

a. 2+4

b. -2+2

c. 4+5

d. -6-1

e. -5-7

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