MCS-012 Computer Organisation and Assembly Solved Assignment 2018-2019

Course Code : MCS-012
Course Title : Computer Organisation and Assembly
Language Programming
Assignment Number : BCA(2)/012/Assignment/2018-19
Maximum Marks : 100
Weightage : 25%
Last Dates for Submission : 15th October, 2018 (For July, 2018 Session)
15st April, 2019 (For January, 2019 Session)

There are four questions in this assignment, which carries 80 marks. Rest 20
marks are for viva voce. You may use illustrations and diagrams to enhance the
explanations. Please go through the guidelines regarding assignments given in
the Programme Guide for the format of presentation. Answer to each part of the
question should be confined to about 300 words. Make suitable assumption, if
any.

Question 1 (Covers Block 1)
(a) What are fixed point numbers in a computer system? Why are negative fixed point
numbers represented in complement form? Give examples of fixed point numbers
(positive as well as negative) assuming the size of the notation to be 8 bits
(including sign bit).
Perform the following arithmetic operations using signed 2’s complement 8 bit
representation. (Please note that the numbers given below are in decimal notation)
i) Add –30 and –98
ii) Subtract –79 from 45
Please indicate overflow if it is occurs. Explain how have you identified the
overflow? (2 Marks)
(b) Perform the following conversion of numbers:
i) Decimal (56789123)10 to binary and hexadecimal
ii) Hexadecimal (ABCDEF0)H into Octal.
iii) ASCII string “Subject: Computer %$ Sc.” into UTF 8 string
iv) Octal (345123)O into Decimal
(2 Mark)
(c) Design a circuit for the following function:
F(A, B, C, D) = Σ (2,3,4, 5, 10, 11, 12, 13)
Draw the truth table. Use the Karnaugh’s map to design the circuit and draw it
using AND, OR and NOT gates. (4 Marks)
(d) What is the need of a parity bit? Explain with the help of an example. How many
parity bits are needed to detect and correct a single bit error in a 8-bit data?
Explain the process of correction of Single bit error with the help of an example
which is not from your Unit. (4 Marks)
(e) Design a two bit down counter (a sequential circuit). The counter states are 11,
10, 01, 00, 11, 10, 01, 00, 11…You should show the state table, state diagram, the
k-map for circuit design and logic diagram of the resultant design using D flipflop
or J-K flip flop. (4 Marks)
(f) What is floating point number? What is the difference between Single precision
and double precision floating point numbers? What is a representation for Zero in
IEEE 754 single precision standard. Represent (-23456.05)10 and (0.00025)10 in
IEEE 754 single precision format. (4 Marks)
Question 2 (Covers Block 2)
(a) A RAM has 1M rows each having 16 cells:
(i) How many data input and data output lines does this RAM needs? Explain your
answer.
(ii) What is the capacity of RAM in bytes.
(iii) How many address lines are needed for this RAM? Give reason in support of
your answer. (2 Marks)
(b) A computer has 1 MB RAM and has a word size of 16 bits. It has cache memory
having 8 blocks having a block size of 32 bits. Show how the main memory
address 0001 1001 1110 1101 0001 will be mapped to cache address, if
(i) Direct cache mapping is used
(ii) Associative cache mapping is used
(iii)Two way set associative cache mapping is used.
(4 Marks)
(c) What is the need of DMA in a Computer? How is DMA different than that of
Interrupt driven I/O technique? Assume that a new computer supports few bytes
of input from multiple user’s, which of the three I/O techniques is most suitable
for this computer? Justify your answer. (4 Marks)
(d) Assume that a disk has 1000 tracks with each track having 64 sectors and each
sector is of size 512 K. A file having the name bcamca.txt is of size 16 M. Assume
that disk has four free continuous clusters of 8 sectors each. How can this file be
given the space on the disk? Also show the content of FAT after the space
allocation to this file. You may make suitable assumptions. You may assume the
cluster size as 2 sectors, if needed. (4 Marks)
(e) Explain the following giving their uses and advantages/disadvantages.
(Word limit for answer of each part is 50 words ONLY) (6 Marks)
(i) Memory Interleaving
(ii) RAID
(iii) IDE interface
(iv) CAV and CLV in the context of disks
(v) Passive and Active matrix display
(vi) Advantages and disadvantages of Ink-jet printers
Question 3 (Covers Block 3)
(a) A computer has a single core processor having 8 General purpose registers and 8
additional special purpose registers. The machine has 64 KB RAM. The size of
each register and memory word is 16 bits each. An instruction of the machine is of
fixed length and is equal to two memory words. Each instruction of the machine
has two operands – one memory operand and second register operand. Memory
operand uses direct addressing; however, register operand can use either register
direct or register indirect addressing. (Please note that if register operand uses
indirect addressing, then stated register contains the address of the operand in the
memory.) An instruction of a machine consists of operation code bits, One
addressing mode bit and one register operand and one memory operand. The
addressing mode bit specifies addressing mode as:
Addressing mode bit Register Operand Memory Operand
0 Indirect Direct
1 Direct Direct
Five of the special purpose registers perform the task as Program Counter (PC),
Accumulator (AC), Memory Address Register (MAR), Data Register (DR) and
Flag registers (FR). The size of Integer operands on the machine may be assumed
to be of equal to size of accumulator register. In order to execute instructions the
machine has an Instruction Register (IR) of size 32 bits as each instruction is of
this size. Perform the following tasks for the machine.
(i) Design suitable instruction formats for the machine. Specify the size of
different fields that are needed in the instruction format. Also indicate how
many different operations can be coded for this machine. Give reasons in
support of your answer. (3 Marks)
(ii) Put some valid values in certain registers and memory locations and
demonstrate examples of different addressing modes of this machine. (1 Mark)
(iii)Assuming that the instructions are first fetched to Instruction Register (IR) and
memory operands is brought to DR register; indirect operand is brought to
AC; and result of operation is stored in the AC register; write and explain the
sequence of micro-operations that are required for fetch cycle and execute
cycle of an instruction which performs addition of two operands having
addressing mode bits as 0. Please note that one of the operand is Indirect
Register Operand and the second is a direct memory operand. Make and state
suitable assumptions, if any. (6 Marks)
(b) Assume that you have a machine as shown in section 3.2.2 of Block 3 having the
micro-operations as given in Figure 10 on page 62 of Block 3. Consider that R1
and R2 both are 8 bit registers and contains 01111011 and 10000100 respectively.
What will be the values of select inputs, carry-in input and result of operation
(including carry out bit) if the following micro-operations are performed? (For
each micro-operation you may assume the initial value of R1 and R2 as given
above) (2 Marks)
(i) Subtract R2 from R1with borrow
(ii) Exclusive OR of R1 and R2
(iii)Shift Left R1 twice
(iv)Increment R1
(c) Explain the structure of Control Unit with the help of block diagram. What is the
role of control signals in instruction execution? (3 Marks)
(d) Explain the reasons of reducing complexity in a RISC machine. What are the
advantages of using large register file in RISC? How RISC machine’s instruction
pipelining different from other machine’s instruction pipelining? (2 Marks)
(e) A RISC machine has 128 registers out of which 32 registers are reserved for the
Global variables and 32 for Instruction related tasks. This machine has been
designed to have 8 registers for storing two input parameters, two output
parameters and four local variables for function call. Explain with the help of a
diagram, how the overlapped register window can be implemented in this machine
for function/procedure calls. You must explain how the parameters will be passed
when a function calls another function. How many levels of calls such a machine
can support? (3 Marks)
Question 4 (Covers Block 4)
(a) Write a program using 8086 assembly Language (with proper comments) that
accepts four characters entered using the keyboard. It checks if all these
characters are decimal digits. If all of them are decimal digits, then program
calculates the equivalent hexadecimal value of the four digit number that has been
input. The program then displays this hexadecimal number on the screen. Make
suitable assumptions, if any. (7 Marks)
(b) Write a program using 8086 assembly Language (with proper comments) that
passes AL register value as parameter to a near procedure named DIVZERO,
which checks if this passed AL value is zero or not. In case this value is ZERO
program is terminated, otherwise same value is returned in AL register. Make
suitable assumptions, if any. (7 Marks)
(c) Explain the following in the context of 8086 Microprocessor (6 Marks)
(i) The supported memory in 8086 is 1 MB whereas instruction offset is only 16
bits
(ii) Processing of Interrupts using IVT
(iii) Indirect addressing modes of 8086 microprocessor