1.3.6 Operating Systems

Question 1

State 5 functions of an operating system

Answer 1

• Provides a user interface for applications
• Opens, closes and installs software
• Manages the hardware and peripherals
• Manages memory e.g. loading programs into RAM
• Manages processor time allocation
• Manages interrupts and error handling
• Manages file handling e.g. organising, saving and deleting
• Manages security e.g. logging on and passwords
• Manages user accounts

Question 2

Why do we need an Operating System?

Answer 2

• Allows a user to communicate with the computer using hardware
• Provides the user with a user interface for interaction with the computer
• Allows for multitasking and handles interrupts

Question 3

What is Virtual Memory

Answer 3

• When RAM is full a section of the hard disk is used to allow more programs to be loaded.
• It is much slower than RAM.

Question 4

What is a device driver?

Answer 4

• A piece of software that allows peripheral devices to communicate with the OS
• Translates signals to/from peripherals to something the OS can understand

Question 5

What is spooling?

Answer 5

• Simultaneous Peripheral Operations On-Line
• Data are temporarily held in a buffer waiting for an output device to access it e.g. printer

Question 6

What is memory management?

Answer 6

Operating system assigns blocks of memory to programs running in a computer

Question 7

What is scheduling?

Answer 7

Operating system determines the order in which the programs should use the CPU and how much time is allocated to each one

Question 8

What is polling?

Answer 8

• Operating system regularly checks each peripheral device in turn to discover whether it needs the attention of the operating system.
• Less efficient CPU use than interrupts

Question 9

What is a Disk defragmenter?

Answer 9

• Moves part of files around so all parts are stored together
• Free memory space is collected together

Question 10

What is a buffer

Answer 10

Temporary memory which stores data until it is ready to be used.

Question 11

What is an interrupt?

Answer 11

Interrupts are signals sent to the CPU or operating system
They can be sent from a device (e.g. printer - run out of paper) or software (e.g. email client, email arrived)
The signal is used to request processor time
It enables multitasking to be carried out on a computer

Question 12

Explain how an interrupt is generated and handled when a key is pressed on a keyboard

Answer 12

• A key is pressed that presses a switch
• The key press completes a circuit
• The location of the keypress is calculated
• The location of the keypress is used to look up the binary ASCII value
• The binary ASCII value is then sent to a buffer to wait to be processed
• An interrupt is then sent to the processor to let it know there has been a key press
• The binary ASCII value is then processed by the CPU
• The CPU then returns to the previous process.

Question 13

What is multitasking?

Answer 13

When multiple tasks share the processor

Question 14

What is multiprogramming?

Answer 14

Running more than one program at a time