Systems Software

Question 1

What function does an OS provide?

Answer 1

user interface
memory management
interrupt handling
processor scheduling

Question 2

How paging and segmentation are similar

Answer 2

Both allows programs to run despite insufficient memory
both stored on disk
both transferred into memory when needed

Question 3

Paging features

Answer 3

fixed size
are made to fit sections of memory
are physical divisions

Question 4

Segment features(opposite of paging)

Answer 4

Different size
complete sections of programs
are logical divisions

Question 5

Problems with segments and paging

Answer 5

If psychical memory is running low virtual memory has to be used.If more time is spent moving pages/segments in and out of the memory to the disk(thrashing) than actually processing the instructions,the computer will be very slow

Question 6

Types of interupts

Answer 6

Software

Hardware

Question 7

Aims of scedhuling

Answer 7

To provide an acceptable response time to all users
To maximise the time the CPU is usefully engaged
To ensure fairness on a mutli-user system

Question 8

Scheduling;What is Round robin?

Answer 8

Each job is allocated a time slice (by FIFO) during which it can use the CPU’S resources
If the job has not been completed by the end of its time slice, the next job is allocated a time slice

Question 9

Scheduling; What is Shortest remaining time?

Answer 9

The time to completion is estimated as each new job arrives
The job with the shortest remaining time to completion is executed,meaning that a shorter new job can take over from the current process

Question 10

Scheduling;What is Shortest job first?

Answer 10

Also known as ‘Shortest process next’
As with shortest remaining time the total execution time of each job is estimated by the user
The waiting job with the smallest total execution time is executed when the current job completes

Question 11

Scheduling;What are Multi-level feedback queues?

Answer 11

Multiple queues are created with different priority levels
If a job uses too much CPU time its is moved to a lower priority queue
Processes can also be moved to a higher priority queue f they have waited a long time

Question 12

What is paging

Answer 12

Available memory is divided into fixed chunks called pages.Each page has an address. A process loaded into RAM is allowed sufficient pages(they may not be next to each other)

Question 13

What is first come first served?

Answer 13

The first job to arrives is executed until it completes

Question 14

What is a distributed OS

Answer 14

Allows multiple computers to work together on a single task

Question 15

What is a embedded OS

Answer 15

Designed to run on embedded systems rather then general purpose computers. An embedded system is a computer that forms a part of a device such as a washing machine,vending machine or car’s engine management system

Question 16

What is a multi-tasking OS

Answer 16

Can run multiple programs simultaneously

Question 17

What is a multi-user OS

Answer 17

Allows multiple users to use a system and its resources simultaneously. It is the simultaneous aspect that is important.An operating system that allows multiple use accounts but only one person to use the system at a time is not classed as a multi-user operating system

Question 18

What is a Real time OS

Answer 18

Designed to carry out actions within a guaranteed amount of time even when left running for long periods.Usually the expected response time is within a small fraction of a section

Question 19

What is BIOS

Answer 19

Stands for’Basic Input Output System’
The fundamental purpose of the BIOS in modern PCs is to initialise and test the system hardware components and to load the OS(or the key parts of it) from the hard disk into RAM. BIOS was historically used to provide an abstraction layer which allowed a consistent way for application programs and the OS to interact with input-output systems(not used after loaded)

Question 20

Where is BIOS stored

Answer 20

BIOS is the program stored in EPROM(Erasable Programmable Read-Only Memory)

Question 21

What are virtual machines

Answer 21

A virtual machine can be defined as any instance where software is used to take on the function of the machine, including executing intermediate code or running an operating system within another to emulate different hardware

Question 22

What are device drivers

Answer 22

Operating systems are expected to communicate with a wide variety of devices, each with different models and manufacturers.It would be impossible for the makers of operating systems to program them to handle all existing and future devices.This is why we need device drivers.A device driver is a piece of software, usually supplied within a device that tells the OS how it can communicate with the device
Example :Printer