Csc 205 introduction to operating system

Question 1

What is an os

Answer 1

Is a software component of a computer system responsible for the management and coordination of activities and resource sharing of the computer system

Question 2

Show the diagram that shows the relationship between os and the computer system

Question 3

Function of os

Answer 3

1)Memory management- it is responsible for the management and allocation of the computer primary memory
2)Device management - it is responsible for managing the computer input and output devices including the transfer of data between the devices and the cpu
3)File management - it is responsible for the organization storing and retrieving of data stored in secondary storage devices like flash drive and hard disks
4) User interface - it is responsible for the provision of a friendly user interface to allow the user to interact with the computer system efficiently
5) Security - it is responsible for protecting the computer from unauthorized access and ensuring data security and integrity
6) Processor management- it is responsible for the management and scheduling of the processor to ensure efficient utilization

Question 4

Goals of an os

Answer 4

. Efficiency
. Reliability
. Extensibility
. Convenience
. Resource allocation
. Security

Question 5

What are the primary structures of OS

Answer 5

1) monolithic structure
2)layered structure
3) micro kernel structure
3) modular structure

Question 6

What is monolithic structure

Answer 6

In this structure the entire os is part of a single code base within the kernel

Question 7

Characteristics of monolithic structures

Answer 7

1) it had high performance
2) it is less modular

Question 8

What is the layered structure

Answer 8

It is a is structure in which the os is divided into multiple layers where each layers have specific tasks and only interacts with its adjacent layer

Question 9

The characteristic of layered structure

Answer 9

Enhances modularity

Question 10

What is micro kernel structure

Answer 10

Only the most essential os structure like basic memory management and inter process communication are kept In the kernel or nucleus, other services like file management and device drivers are run in the user space

Question 11

Characteristics of micro kernel

Answer 11

1) improves stability and security as system failure in the user space does not crash the entire os
2) more IPC required

Question 12

What is modular structure

Answer 12

Allows for the loading and unloading of os structures called modules, in this the os is divided into distinct undefended modules that performs a specific function or service .

Question 13

Where can modules be found

Answer 13

They can be found organized around the core kernel

Question 14

Characteristics of modular structures

Answer 14

1) flexible and efficient
2) it is popular among systems that require flexibility and upgradability

Question 15

Define the os kernel with diagram

Answer 15

Kernel is the core component of the computer os that serves as a bridge between the computer software ware and hardware, managing systems resources and the communication between hardware and software components

Question 16

Function of the kernel

Answer 16

1) it provides the lowest level abstraction layer for computer resources like memory, cpu and I/o devices
2) it provides features for low level scheduling process, Interprocess communication etc
3) it provides method for synchronization
4) it provides running program with a method to make request to access these facilities

Question 17

List and explain the types of kernel

Answer 17

1) monolithic kernel - all the os are combined and stored within a single block code within the kernel
2) micro kernel - only important is structure like interprocess communication and basic memory management are stored in the kernel
3) hybrid kernel - combine elements of monolithic and micro kernel retaining high performance while isolating certain services for modularity

Question 18

Types of os

Answer 18

1) batch
2) network
3) real time
4) distributed
5) time sharing
6) mobile

Question 19

What is a process

Answer 19

A process is simply a program execution or an instance of a program being executed

Question 20

Draw a diagram of the process life cycle

Question 21

List and explain the process state (process life cycle)

Answer 21

1) new/ start - this is the initial state where the process is created
2) ready - the process is waiting to be assigned to a processor
3) running - once it as been assigned to the processor it takes it moves to the running stage and executes its instructions
4) waiting - the process moves to this stage if it has to wait for a resource to be available
5) termination-once the process is done with execution it moves to the termination stage so it’s lobe can be removed from the computer main momory

Question 21

What is a pcb

Answer 21

A process control block contains many pieces of information associated with a specific process

Question 21

list and explain the content of basic pcb with diagram

Answer 21

components of pcb
1)process state- current state of the process
2)program counter- indicates the address of he next instruction to be executed
3) CPU register- used to store the process during execution
4) memory management information- information may include value of base and limit registered, the page tables or the segment table depending on the memory system used
5) io status information- contains list of io devices allocated to the process ,list of open files etc

Question 22

Steps involved in process creation

Answer 22

Initialization, program Loading, memory allocation, setting up process control block, assigning process ID, set up execution context, parent-child relationship, execution, user and kernel mode transition

Question 23

Steps involved in process termination

Answer 23

Exit system call, closing files and releasing resources , Termination status, Process state change, parents process notification, resource reamation , process, table updates, child - process Clean up, Finalization

Question 24

Differences between monolithic and micro kernel structures

Answer 24

Monolithic system services run in the kernel
Less modular
Higher performance
Higher security risk

Micro kernel system
Few services run in the kernel while others run in the user space
Enhances modularity
Lower performance
Lower security risk

Question 25

what is process scheduling

Answer 25

the operating system process scheduling is a crucial part of the computer system that involves managing and determining the order in which processes are executed by the CPU

Question 26

what is the cpu

Answer 26

central component of the computer system responsible for the executing of instructions of a computer program

Question 27

explain briefly process scheduling queues

Answer 27

Process are maintained in queue based on process state. the os maintains individual queues for each process state , and the pcb of all processes in the same state are placed in the same queue . When a process changes states it is unliked from it current queue and placed in the new state queue

Question 28

list and explain the important queue maintained by the os

Answer 28

1] job queue - hold all the processes in the system . when a process enters the system it is moved to this queue
2] ready queue - holds a set of all processes in the systems main memory, ready and waiting to execute
3] device queue- keeps a list of processes waiting for a parti ocular I/o device

Question 28

what are schedulers

Answer 28

schedulers are special system software that handles process scheduling in different ways

Question 29

types of schedulers and explain

Answer 29

1] longterm/ job scheduler - selects processes from a pools and loads then into memory for executions

2] short term/ cpu scheduler - selects among processes ready to execute and assigns a cpu to them

3] medium term scheduler - removes suspended processes to make space for more process, the suspended process is then move to external storage devices . this process is called swapping

Question 30

what is context switching

Answer 30

this involves switching the cpu to another process by saving the state of the old process and loading the saved state of the new process

Question 31

list the types of scheduling algorithm employed by the os

Answer 31

1] first-come, first- served - it is non preemptive. processes are scheduled in the order they arrive
2] shortest-jobs first - it is non preemptive and is the best way to shorten waiting time
3] priority scheduling - each process is assigned a priority and the process with the highest priority are scheduled first
4] round robin- it assigns equal time slices to each process in a circular order handing all process without priority
5] multilevel queue scheduling - processes are divided into priority levels, each queue may have its scheduling algorithm. the process move between queues based on its behaviour and priority
6] multilevel feedback que scheduling - similar to mlc but process can move dynamically between queues based on its behaviour and resource requirement
7] real-time scheduling- designed for systems with real time requirement, where tasks must be completed within a specified time