Functions of an Operating system

Question 1

what is an Operating system ?

Answer 1

an O/S is a system software that manages computer hardware , software resources and provides common programs

Question 2

What does the Operating system provide ?

Answer 2

-User interface
-Memory management
-Interrupt Handling
-Processor scheduling

Question 3

What does user interface do and Memory management ?

Answer 3

user interface hides the complexity of the hardware from the user by providing a user interface .

Memory Management manages the allocation of RAM to the different Programs

Question 4

What are the two types of Memory Management ?

Answer 4

Paging and Segmentation

Question 5

what is paging and segmentation ?

Answer 5

Paging - Available memory is divided into fixed sizes.

Segmentation - Memory is divided into segments which can be different lengths.

Question 6

what are interrupts ? and an ADV and Dis-ADV ?**

Answer 6

An interrupt is a signal that is sent from the software to the O/S

Question 7

explain the process of interrupts using stack ?

Answer 7

When an interrupt is detected the processor stops fetching instructions and instead pushes the Current contents of its registers onto a Stack .

Question 8

what is interuupt priority ?

Answer 8

interrupts have different priorities and will be processed in order of priority .

if a higher priority interrupt occurs whilst an interrupt is being processed, the original interrupts will be pushed onto a STACK

Question 9

what are the types of Processor scheduling methods ?

Answer 9

Round robin
First come First serve (FCFS)
Shortest Job First
Shortest time Remaining (STR)

Question 10

Name the types of operating systems ?

Answer 10

Multi-use
Distrubuted
Multi-tasking system
Mobile O/S

Question 11

what is a mobile O/S ?

Answer 11

a smart phone is a computer with a multi-tasking O/S

Question 12

what is a distributed O/S ?

Answer 12

can co-ordinate the processing of a single job across multiple computers

Question 13

what is real time operating system ?

Answer 13

this is O/S that operates in real time , this is often used in safety crucial environments .

Question 14

what is open software and closed software ?

Answer 14

Open source- this allows anyone to access its source code
- the software is licence but free to use

closed source - this does not allow anyone to access its source code.
-users must pay the person/ company the copyright for a license to use the software

Question 15

what does processor scheduling and interrupt handling do ?

Answer 15

• processor scheduling allows multi-tasking and ensures a fair share of CPU time.
• interrupt handling changes what is being processed by the CPU on a priority basis.

Question 16

what is a paging table ?

Answer 16

a paging table keeps track of the logical and physical locations of memory where each block is held in memory.

Question 17

explain how it is possible for a single processor to appear to be multi-tasking?

Answer 17

• by using processor scheduling this allocated the use of ram which gives the illusion that it is multitasking

Question 18

what is the aim of scheduling algorithms in a multi-tasking system ?

Answer 18

• To provide an acceptable response time to all users
• to ensure fairness on a multi-user system

Question 19

what is a bytecode?

Answer 19

a byte code is an intermediate code between high level and machine code . A byte code interpreter translates the bytecode to machine code

Question 20

what is meant by a virtual machine ?

and how does a virtual machine protect us from potential viruses ?

Answer 20

• software implementation emulating the behaviour of particular hardware.
• a virtual machine will pick up suspicious code(virus) found and will not pass it into the machine to be processed

Question 21

what is the difference between systems software and applications software?

Answer 21

• system software is needed so that the system can operate and function properly whereas the application software is needed to provide the user with applications

Question 22

what is the complier?
what is the assembler ?

Answer 22

-The compiler translates from high level language to machine code.( the whole program at once )
-assembler translates assembly language to machine code( line by line)

Question 23

what is lexical analysis?

what is syntax analysis?

what is a symbol table ?

Answer 23

• lexical analysis is removing unnecessary white space and comments.
• syntax analysis is checking if code is against rules of language.
• A symbol table stores key words and data types .

Question 24

what is BIOS ?

Answer 24

This stands for basic input output system
-This is responsible for loading the O/S when the computer is not on.

This bios loads the O/S from the ROM and send to RAM

Question 25

what is a device driver ?

Answer 25

A device driver is software that will translate computer instructions to another hardware device .
e.g a laptop sending instructions to a Printer
-This is a software that tells the O/S how to communicate with a device.

Question 26

what is virtual machine ?

Answer 26

A virtual machine is a program that has the same functionality as a physical computer e.g( Java code)

Question 27

what does the utillity Software consit of:

Answer 27

-antivirus
-disk fragmentation
-Backup
-Compression

Question 28

explain how developers could use virtual machines?

Answer 28

developers can use virtual machines as information/guidance to improve a system . virtual machines emulate software therefore they could use this emulation and discover any faults in order to improve .

Question 29

what is the difference between a queue daa structure and a stack data structure ?

Answer 29

A queue is First In First Out (FIFO), whereas a stack is Last In First Out (LIFO)

Question 30

explain how a system appears to be multi-tasking ?

Answer 30

• processor scheduling- this is allows multi-tasking and fair share of CPU time .

Question 31

what does by reference mean , and passing by value?

Answer 31

• passing by reference means that the functions receiveds the memory location of the variable
  -passing by value means that the function receives a copy of the variable