June, 2001: CS-64: Question Paper >>> Introduction to Computer Organisation

BACHELOR IN COMPUTER APPLICATIONS

Term-End Examination

June, 2001

 CS-64: INTRODUCTION TO COMPUTER ORGANISATION

Time : 3 Hours

Max. Marks : 75

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Note : There are six questions in this paper. Question one is compulsory and carries 30 marks. Answer any three questions from the rest.

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1. (a) Perform the following arithmetic operations using 8 bit registers. Use binary signed 1's complement notation. Indicate overflow/underflow, if any.

(i) 29 + (— 49)

(ii) 27 — 101

(iii) — 28 + (—1OO)

(iv) 68 + (—75)

(b) Simplify the following Boolean function in sum-of-product from using tour variable Karnaughs map. Draw the resulting logic diagram.

F (A. B. C, D) = ∑(0, 5, 6, 7, 8, 9, 10, 11, 12, 15)

Please note that the symbol ∑ signifies the minterms whose decimal equivalent is listed in the parentheses. Produce a value 1 in the K map for the function.

(c) Describe the need of a multiplexer in a system. How is a multiplexer different from a decoder? Draw the logic diagram of a 2 x 1 multiplexer and 2 x 4 decoder.

(d) Write a program in 8086 assembly language to find whether a tour digit packed BCD number is divisible by either 3 or 5.

(e) How can you input integers, characters and strings through keyboard for an assembly language (8086 assembly language) program? Explain with an example.

(f) What is a micro-operation? Is it related to a micro-instruction? What is a horizontal micro-instruction? What are the advantages of horizontal micro-instruction over vertical micro-instruction? Describe the term micro-program.

2. (a) “ROM although is permanent memory, yet is a combinational circuit." Justify the above statement by giving example of 2 word — 4 bit ROM. How is a cell of ROM different than that of RAM?

(b) Write a program in 8086 assembly language to find frequency of capital alphabets in a long string. Make suitable assumptions, if any.

(c) What is a zero address instruction? How can such instructions be executed? Describe a machine organisation which can have most of its instructions as zero address instructions.

3. (a) What is the need of an Input/output processor? Suggest a method by which an Input/output processor can be connected to slow devices. Can an Input/output processor be replaced by a DMA module? Justify your answer.

(b) Design a combinational circuit for a decision function, which takes four input bit values and generates a value 1 if two or more bit values are 1; otherwise the function outputs a zero value. Draw the resulting logic diagram.

(c) What are the displacement addressing modes? Explain with the help of an example each. Suggest the addressing modes that can be used in 8086 to handle arrays efficiently. Explain by giving an example.

4. (a) Draw the logic circuit for one stage of full adder: Draw the block diagram for adding two tour bit numbers.

(b) Write a program in 8086 assembly language to add two four digit unpacked BCD numbers.

(c) Design a floating point number format for the following requirements;

Base: 2

Mantissa: Normalized, should be large enough to hold 4 significant decimal digits.

Exponent: Biased exponent in the range of 1- 25

Precision: Single

Make suitable assumptions if any.

5. (a) What is parity bit ? How is it used in Single Error Correction Code? How do you determine the size of SEC code for a giver bit of data?

(b) Compare and contrast the following.

(i) Associative memories versus interleaved memories.

(ii) 2D chip organisation versus 2% D chip organisation.

(iii) DRAM versus SRAM.

(c) What is arbitration? Describe the method of polling arbitration. Compare and contrast Polling arbitration mechanism to that of Daisy chaining and Independent requesting.

6. Write short notes on the following:

(a) Mapping of Cache blocks

(b) Wilkes control

(c) Selective set, Selective clear and Mask operations

(d) Fetch cycle of an instruction

(e) Peripheral processors and Co-processors