Test Papers / Previous Question Papers of IGNOU CS01 Computer Fundamentals December 2005

PGDCA / MCA (I Yr) / BCA
Term-End Examination

December, 2005

CS01 : Computer Fundamentals

Time: 3 hours
Maximum Marks: 75

1. (a) Express (- 19,750) in 2's complement notation (16-bit). (2)

(b) Make the logic diagram of a A-bit serial shift register using J-K flipflops. Show the steps to shift the binary number 1001, through this shift register. (7)

(c) Why does DMA have priority over the CPU when both request a memory transfer ? (3)

(d) Wriie an 8086 assembly language program to 'multiply a two-digit unpacked BCD number with a single-digit BCD number. (6)

(e) Explain the sequence of micro-operations including parallelism (if any), for the "execute cycle" of the ''subroutine call" and "return instructions". (6)

(f) Explain the problems that prevent a RISC pipeline from achieving maximum speed. How can these problems be handled ? (6)

2. (a) A digital computer has memory unit of 64 K x 16 and cache memory of 1 K words. The cache uses direct mapping with a block size of 4 words.
(i) How many bits will there be in tag, index, block and word fields of the address format of cache?
(ii) How many blocks can cache accommodate? (5)

(b) Consider the following hexadecimal values stored in the memory :

What would the value of the operand be if the instruction is
(i) LOAD INDIRECT 0100?
(ii) LOAD 0500 ? (2)

(c) What is the purpose of an index register ? Explain this with the help of an example. How is it related to the auto-increment mode of addressing ? (3)

(d) In the following computations, a and b are external inputs and z is the final output, x and y are intermediate results.
x<-a*a, y<-b*b, z<-(x+y)/(x-y)
Draw the data flow graph for this code. (5)

3. (a) Draw the logic diagram, using AND, OR, NOT gates, for a function that takes four binary input values, outputs 1 if zero, two or all the four input values are 1, and outputs 0 otherwise. (5)

(b) What are the various read/write conflicts in a multiprocessor system ? How are they overcome ? (4)

(c) Write a program to evaluate the following expression using an evaluation-stack architecture machine. (6)
A * B + C - D / E + F
Assume that the machine contains instructions for PUSH, POP, MULTIPLY, DIVIDE, ADD and SUBTRACT.

4. (a) Write a program in 8086 assembly language that counts the number of occurrences of a given letter in a string. You can assume that the string is stored inthe data segment and is terminated by a $ chatacter.The letter that is to be searched for in a string is stored in AL register. The result of the computation above should be stored in DX register. (8)

(b) Determine the number of steps required to evaluate the arithmetic expression : (4)
S = A[1] ⊗ b[1] + A[2]*B[2] + A[3]*B[3] + A[4] ⊗ B[4]
in the following computer systems :
(i) An SISD system with general purpose registers, (ii) An MIMD system with four processors.

(c) Explain the concept of associative memory. (3)

5. (a) Write an 8086 assembly language program for performing the following operations : (3)
(i) Switch on heater if temperature goes below 10ºC.
(ii) Switch off heater if temperature goes above 50ºC.
Assume suitable variables.

(b) Explain the various head mechanisms of hard disk. (3)

(c) With the help of a diagram explain the general structure of an I/O rnodule or interface. (4)

(d) List the differences between (5)
(i) CRT and LCD display
(ii) Laser printer and Dot matrix printer