UNIX QUESTION AND ANSWER
Here's a breakdown of
the UNIX and Shell Programming question paper, along with some potential
answers:
Section A (MCQs/Fill in
the blanks/Very short answer questions)
· (a) A
shell variable cannot start with a number or a special symbol other than an underscore.
· (b) The
first line of a shell script starts with a hash (#).
· (c) The
shell metacharacters $# and $* represent
the number of arguments passed to the script and the list of all arguments,
respectively.
· (d) Two
ways to identify if a file is ordinary or a directory are:
o
Using the ls -l command to see the
file type (e.g., - for regular file, d for
directory).
o
Using the file command to get
detailed information about the file type.
· (e) UNIX
is written in C.
· (f) The
three modes of operation in vi are command mode, insert mode, and visual mode.
Other editors available under UNIX include emacs, nano, and pico.
· (g) To
list all filenames starting with 'a', 'b', or 'k', you can use the
command ls [abk]*.
· (h) . represents
the current directory, and .. represents the
parent directory.
· (i) To
remove all empty directories in the path dir1/dir2/dir3/dir4, you
can use the command rm -r dir1/dir2/dir3/dir4.
· (j) To
make a variable unchangeable in a shell script, use the readonly command.
For example, readonly myvar.
Section B (Short Answer
Questions)
· (a) Explain
UNIX file system.
· (b) How
to view current permissions of a file or directory:
o
ls -l to see permissions in human-readable format.
o
chmod 777: Sets all permissions (read, write,
execute) for owner, group, and others.
o
chmod 755: Sets read, write, and execute
permissions for owner, read and execute for group and others.
o
chmod +x: Adds execute permission for all
users.
· (c) The
UNIX system variables mentioned signify:
o
HOME: Home directory of the user.
o
PS1: Primary prompt string.
o
PATH: Search path for commands.
o
TERM: Terminal type.
o
MAILCHECK: Interval to check for mail.
· (d) The
output of the shell script will be: set Only God is in a position to look
down upon someone. echo $0 $10 $11 $
Here's a breakdown of
the UNIX and Shell Programming question paper, along with some potential
answers:
Section A (MCQs/Fill in
the blanks/Very short answer questions)
· (a) Which
command is used to display and create the file?
o
Answer: (ii) vi
· (b) What
are the 3 modes of operation of vi?
o
Answer: Command mode, insert mode, and visual mode.
· (c) Which
command is used with the filename 'note' to remove the executable permission
from user and assign the read permission to the group and others?
o
Answer: (i) chmod u-x,go+r note
· (d) What
do the terms UID, PID, and PPID stand for? For a particular process which is
currently executing, how can you obtain these values?
o
Answer: UID = User ID, PID = Process ID, PPID = Parent
Process ID. You can use the ps command to get
these values.
· (e) Which
of the following is not a filter?
o
Answer: (ii) cal
Section B (Short Answer
Questions)
· (a) Explain
UNIX file system.
· (b) How
to view current permissions of a file or directory:
o
ls -l to see permissions in human-readable format.
o
chmod 777: Sets all permissions (read, write,
execute) for owner, group, and others.
o
chmod 755: Sets read, write, and execute
permissions for owner, read and execute for group and others.
o
chmod +x: Adds execute permission for all
users.
· (c) The
UNIX system variables mentioned signify:
o
HOME: Home directory of the user.
o
PS1: Primary prompt string.
o
PATH: Search path for commands.
o
TERM: Terminal type.
o
MAILCHECK: Interval to check for mail.
· (d) The
output of the shell script will be: set Only God is in a position to look
down upon someone. echo $0 $10 $11 $
Section C (Long Answer
Questions)
· (a) Explain
UNIX architecture and types of shells.
· (b) Define
shell scripts, their advantages, disadvantages, and types.
· (c) Differentiate
between System Call and Library Call.
· (d) Write
a shell script to calculate the area of a rectangle and triangle.
SECTION A
1. (a) Which
command is used to extract specific columns from a file? Answer: cut
2. (b) Describe
the stages that the client and server go through to establish a connection and also
explain the following system calls: Answer:
· Socket: Creates
a socket descriptor to represent the endpoint for communication.
· Bind: Assigns
an IP address and port number to the socket descriptor.
· Listen: Causes
the socket to listen for incoming connections.
· Accept: Accepts
a connection request from a client.
· Connect: Initiates
a connection to a server.
3. (c) Define
independent and cooperative process in UNIX? Answer:
· Independent
Process: A process that runs independently of other processes.
It has its own memory space and resources.
· Cooperative
Process: A process that shares resources and communicates with
other processes. It can be interrupted by the operating system to allow other
processes to run.
4. (d) While
executing the shell script either the LOGNAME or the UID is supplied at the
command prompt. Write the shell script to find how many terminals has this user
logged in. Answer:
#!/bin/bash
if [ "$1" = "" ]; then
echo "Please
provide LOGNAME or UID as argument"
exit 1
fi
if [ "$1" -gt 0 ]; then
who | grep
"$1" | wc -l
else
who | grep
"$1" | wc -l
fi
5. (e) What
do you mean by Daemon? How will you kill a Daemon? Answer:
· Daemon: A
background process that runs continuously, typically providing a service.
· Killing
a Daemon: Use the kill command with the
process ID (PID) of the daemon. You can find the PID using the ps command.
6. (f) What
would be the output of the following statements?
set who am i
echo $
Answer:
who am i
7. (g) For
the command line arguments dog parrot cuckoo write
the shell script which prints each argument in a separate line. Answer:
#!/bin/bash
for argument in "$@"; do
echo
"$argument"
done
Operating
system
SECTION B
1. Attempt any TWO of
the following questions:
a. Explain critical
section problem. Write down requirements for solution to critical section
problem:
·
Critical Section Problem: A
situation where multiple processes access a shared resource simultaneously,
leading to unpredictable results.
·
Requirements for Solution:
o
Mutual Exclusion: Only
one process can access the critical section at a time.
o
Progress: If
no process is in the critical section, a process that wants to enter should be
allowed to do so.
o
Bounded Waiting: There
should be a limit on the number of times a process can be prevented from
entering the critical section.
b. Explain in detail the
implementation of Paging. Differentiate between internal and external
fragmentation:
·
Paging: A
memory management technique that divides physical memory into fixed-sized
blocks called frames and logical memory into fixed-sized blocks called pages.
·
Internal Fragmentation: When
a process is allocated a frame, there may be some unused space within that
frame.
·
External Fragmentation: When
there is enough free memory to allocate a process, but it is not contiguous,
leading to wasted memory.
c. Differentiate between
long, medium, and short-term process scheduling:
·
Long-Term Scheduling (Job Scheduling): Determines
which processes are admitted into the system.
·
Medium-Term Scheduling (Swapping): Decides
which processes to swap out of memory to make room for other processes.
·
Short-Term Scheduling (CPU
Scheduling): Selects the next process to be executed by the CPU.
d. List names of five
operating systems (OS). Discuss any two OS in detail with examples:
·
Windows: A
popular operating system for personal computers.
·
Linux: An
open-source operating system known for its flexibility and security.
·
macOS: An
operating system developed by Apple for its Macintosh computers.
·
Android: A
mobile operating system based on Linux.
·
iOS: A mobile operating
system developed by Apple for its iPhones and iPads.
2. Attempt any ONE of
the following questions:
a. What is the Banker's
algorithm? Consider the following scenario of a system:
·
Banker's Algorithm: A
resource allocation algorithm that prevents deadlocks by ensuring that
processes request and release resources in a safe manner.
b. How can a critical
section problem be related to a real-life scenario? Illustrate with an example:
·
Real-life scenario: Two
people trying to use the same restroom at the same time.
·
Critical section problem: Both
people trying to access the restroom at the same time, leading to a conflict.
3. Attempt any ONE of
the following questions:
a. What are the
necessary conditions for having deadlock in the system? Explain in detail:
·
Mutual Exclusion: Only
one process can use a resource at a time.
·
Hold and Wait: A
process holds a resource and waits for another resource.
·
No Preemption: A
resource cannot be forcibly taken away from a process.
·
Circular Wait: A
circular chain of processes exists, where each process is waiting for a
resource held by the next process in the chain.
b. Explain memory
management. Why paging is used?
·
Memory Management: The
process of allocating and deallocating memory to processes.
·
Paging is used to:
o
Overcome the limitations of contiguous memory allocation.
o
Improve memory utilization.
o
Simplify memory management.
SECTION C
4. Attempt any ONE of
the following questions:
a. Write short notes on:
·
Disk Structure: The
organization of data on a disk, including tracks, sectors, and cylinders.
·
Disk Reliability: The
ability of a disk to store data reliably over time, despite physical failures.
b. How does the
operating system function as a resource manager?
·
CPU Scheduling: Allocating
CPU time to processes.
·
Memory Management: Allocating
memory to processes.
·
I/O Device Management: Managing
I/O devices and their access.
·
File System Management: Organizing
and managing files on storage devices.
5. Attempt any ONE of
the following questions:
a. What is a semaphore?
Write down different types of semaphore:
·
Semaphore: A
synchronization mechanism used to control access to shared resources.
·
Types of Semaphore:
o
Binary Semaphore: Can
have a value of 0 or 1.
o
Counting Semaphore: Can
have a non-negative integer value.
COMPUTER
ORGANIZATION AND ARCHITECTURE
1. (c)
Write an assembly code statement to evaluate the arithmetic statement:
X = (A + B)'(C + D)
Using
a general register computer with 3 address instruction:
ADD R1, A, B // R1 =
A + B
NOT R1 // R1 =
(A + B)'
ADD R2, C, D // R2 =
C + D
AND X, R1, R2 // X = (A + B)'(C + D)
Using
an accumulator (AC) type computer with one address instruction:
LOAD A //
Load A into accumulator
ADD B // Add
B to accumulator
NOT A //
Negate the accumulator
LOAD C //
Load C into accumulator
ADD D // Add
D to accumulator
AND A // AND
the accumulator with the previous result
Using
a stack organized computer with 0 address instruction:
PUSH A
PUSH B
ADD
NOT
PUSH C
PUSH D
ADD
AND
1. (d)
Explain SIMD interconnection network in detail.
A
Single Instruction, Multiple Data (SIMD) interconnection network is a type of
parallel processing architecture where multiple processors execute the same
instruction on different data elements simultaneously. It is commonly used in
vector and array processors.
There
are various types of SIMD interconnection networks, including:
·
Linear Array: Processors
are connected in a linear chain.
·
Ring: Processors
are connected in a circular fashion.
·
Mesh: Processors
are arranged in a two-dimensional grid.
·
Hypercube: Processors
are connected in a multidimensional hypercube.
SECTION
C
2. (a)
Discuss the architecture of 8085 microprocessor in detail.
The
8085 microprocessor is an 8-bit microprocessor that has a 16-bit address bus
and an 8-bit data bus. It has various registers, including the accumulator, the
program counter, the stack pointer, and general-purpose registers. The 8085
also has an instruction set that includes instructions for arithmetic, logical,
and control operations.
2. (b)
What is Virtual Memory? An address space is specified by 24 bits and
corresponding memory space by 16 bits.
·
How many words are there in the
address space? 2^24 = 16,777,216 words
·
How many words are there in the memory
space? 2^16 = 65,536 words
·
If a page consists of 4K words, how
many pages and blocks are there in the system?Number
of pages = 16,777,216 / 4096 = 4096 pages Number of blocks = 65,536 / 4096 = 16
blocks
3. (a)
Find X[K] if x(n) = {2, -5, j, -1} using FFT.
You
can use the Fast Fourier Transform (FFT) algorithm to calculate the Discrete
Fourier Transform (DFT) of the given sequence.
3. (b)
What is a controlled inverter, explain?
A
controlled inverter is a type of inverter that can be turned on or off by an
external control signal. It is often used in digital circuits to implement
logic gates and other functions.
SECTION
C
5. (a)
What is Direct Memory Access (DMA)? Explain its working with proper diagram.
Direct
Memory Access (DMA) is a technique that allows certain hardware subsystems to
access main system memory independently of the CPU. This offloads the CPU from
the task of transferring data between memory and I/O devices, improving overall
system performance.
Diagram:
Working:
1.
DMA Request: The
I/O device sends a DMA request to the DMA controller.
2.
DMA Controller Acquisition: The
DMA controller requests bus access from the CPU.
3.
Bus Acquisition: The
CPU relinquishes control of the bus to the DMA controller.
4.
Data Transfer: The
DMA controller transfers data directly between the I/O device and memory,
without involving the CPU.
5.
DMA Completion: Once
the data transfer is complete, the DMA controller sends an interrupt to the CPU
to signal completion.
5. (b)
Find MAL, if the collision vector is given as 11010100
MAL
(Minimum Address Length) is the minimum number of bits
required to represent all the addresses in a memory system. In this case, the
collision vector indicates that there are 8 memory modules. To address each
module uniquely, we need at least 3 bits (2^3 = 8). Therefore, the MAL is 3.
6. (a)
What is pipelining? Consider the execution of a program of 25000 instructions
in a linear pipeline processor with a clock rate of 50 MHz. Assume that the
instruction pipeline has 5 stages and that one instruction is issued per clock
cycle. Calculate:
·
Speedup Factor
·
Efficiency
·
Throughput
Pipelining is
a technique used in computer architecture to improve instruction throughput by
overlapping the execution of multiple instructions.
·
Speedup Factor: Speedup
Factor = (Ideal execution time without pipelining) / (Actual execution time
with pipelining) Ideal execution time = 25000 instructions * 1 clock
cycle/instruction = 25000 clock cycles Actual execution time = (Initial
pipeline latency + Number of instructions) / Clock rate Initial pipeline
latency = 5 stages * 1 clock cycle/stage = 5 clock cycles Actual execution time
= (5 + 25000) / 50 MHz = 500.1 microseconds Speedup Factor = 25000 / 500.1 =
49.99
·
Efficiency: Efficiency
= (Instruction execution rate) / (Maximum possible instruction execution rate)
Instruction execution rate = 25000 instructions / 500.1 microseconds = 50,000
instructions/second Maximum possible instruction execution rate = Clock rate =
50 MHz = 50,000,000 instructions/second Efficiency = 50,000 / 50,000,000 =
0.001 or 0.1%
·
Throughput: Throughput
= Number of instructions executed per unit time Throughput = 50,000
instructions/second
6. (b)
Draw and explain the working of serial adder and subtractor.
A
serial adder adds two binary numbers bit by bit, starting from the least
significant bit (LSB). A serial subtractor subtracts two binary numbers bit by
bit, starting from the LSB. Both use a full adder circuit, which takes three
inputs (two bits to be added and a carry-in) and produces two outputs (sum and
carry-out).
7. (a)
Write short notes on:
·
Vector Processing: Vector
processing is a type of parallel processing where a single instruction operates
on multiple data elements simultaneously.
·
SIMD Array Processor: A
Single Instruction, Multiple Data (SIMD) array processor is a type of parallel
computer architecture where multiple processors execute the same instruction on
different data elements simultaneously.
7. (b)
What is cache coherence, and why is it important in shared memory
multi-processor systems? How can the problem be resolved?
Cache
coherence is the consistency of data across multiple caches in a shared memory
multi-processor system. It is important to maintain cache coherence to ensure
that all processors have access to the most up-to-date data.
The
problem of cache coherence arises when different processors have different
copies of the same data in their caches, and one processor modifies the data
without updating the other caches. This can lead to inconsistencies and
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Here
are the answers to the questions in the image:
SECTION
A
1.
Attempt ALL parts of the following questions:
a) Define
Register in brief.
A
register is a high-speed storage location within a computer's CPU that holds
data temporarily. It is used to store instructions, data, addresses, or
intermediate results during program execution.
b)
Explain Half Adder in short.
A half
adder is a digital circuit that adds two single-bit binary numbers. It has two
inputs (A and B) and two outputs (Sum and Carry). The Sum output represents the
sum of the two input bits, and the Carry output represents the carry-over bit.
c)
Discuss RTL.
RTL
(Register Transfer Language) is a hardware description language used to
describe the behavior of digital circuits at the register transfer level. It
allows for the specification of how data is transferred between registers and
how operations are performed on that data.
d)
What do you mean by Instruction format?
An
instruction format defines the structure of an instruction in a computer's
instruction set architecture. It specifies the different fields within an
instruction, such as the opcode (operation code), operands, and addressing
mode.
e)
What type of operations can be performed in a stack? Explain with an example.
A
stack is a data structure that follows the Last-In-First-Out (LIFO) principle.
Common operations performed on a stack include:
·
Push: Adding
an element to the top of the stack.
·
Pop: Removing the top
element from the stack.
Example:
Consider a stack of plates. When you add a plate, you place it on the top of
the stack. When you remove a plate, you take it from the top.
f)
Discuss any three types of memory used in a computer system.
Three
common types of memory used in a computer system are:
·
RAM (Random Access Memory): Volatile
memory used to store data and instructions currently being used by the CPU.
·
ROM (Read-Only Memory): Non-volatile
memory used to store permanent instructions and data, such as the BIOS.
·
Cache Memory: High-speed
memory that stores frequently accessed data to improve system performance.
·
g)
Enlist five Input/Output operations in a computer system.
Five
common input/output operations are:
·
Keyboard input
·
Mouse input
·
Monitor output
·
Printer output
·
Disk drive input/output
h)
Elaborate interrupt cycle.
An
interrupt cycle is a sequence of events that occurs when a device interrupts
the CPU to request service. The interrupt cycle typically involves the
following steps:
1.
Interrupt request: The
device sends an interrupt signal to the CPU.
2.
Interrupt acknowledgment: The
CPU acknowledges the interrupt and saves the current program counter value.
3.
Interrupt service routine (ISR): The
CPU jumps to the ISR associated with the interrupting device.
4.
ISR execution: The
ISR handles the interrupt and performs the necessary actions.
5.
Return from interrupt: The
ISR returns control to the interrupted program.
6.
i)
Discuss the use of Associative Memory?
Associative
memory is a type of memory that allows data to be accessed based on its content
rather than its address. It is used in applications such as cache memory,
translation lookaside buffers (TLBs), and content-addressable memory (CAM).
j)
Enlist six types of Addressing Modes.
Six
common addressing modes are:
·
Immediate addressing: The
operand is directly included in the instruction.
·
Direct addressing: The
operand's address is directly specified in the instruction.
·
Indirect addressing: The
address of the operand is stored in a memory location, and the instruction
specifies the address of this memory location.
·
Register addressing: The
operand is stored in a register.
·
Register indirect addressing: The
address of the operand is stored in a register.
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