Must Know!

Question 0

What does the control unit do?

Answer 0

It is a part of the CPU that is responsible for:

• It decides which instructions to carry out next and fetches it
• It decodes instructions to work out what needs to be done to execute the
• It informs other parts of the CPU, what needs to be done in order for the instruction to be executed. It does this through sending control signals
• it synchronises the actions of the processor using its internal clock

Question 1

Trace tables

Answer 1

When constructing one:
-Each variable must have a column

• Each mode of selection must be accompanied by a Boolean value,
  e. g. If a => 0. This would have the column a => 0 and each row would have a Boolean value.

-Also each loop must have its own column. A count controlled loop must have integers in it’s rows. The other loops would have Boolean values in the rows as they are condition controlled

Question 2

What does the memory unit do?

Answer 2

It stores everything that the computer is gong to use and the data needed for the CPU to carry out instructions

Question 3

What does RAM do?

Answer 3

The RAM is the volatile memory within the memory unit of the CPU

-It’s job is to store program’s that are being used by the computer

Question 4

What is ROM and what does it do?

Answer 4

ROM is the nonvolatile memory of the memory unit in the CPU

• the memory cannot be altered. It tends to be of a small capacity as it doesn’t have to hold large amounts of data
• It consists of program’s that’s allow the computer to start, such as the boot strap loader

Question 5

How do CDs and DVDs work?

Answer 5

A laser reflects on the CD or DVD and the reflection is read on a pitted surface , this is how information is read from an optical disc

Question 6

What does RW mean (optical disks)?

Answer 6

It mean that the contents of the CD or DVD can be erased or rewritten

-this can be used to store back up records that need to be updated on a regular basis

Question 7

What does ROM mean (Optical disks)?

Answer 7

This means that the contents of a CD or DVD be altered

• Manufacturers have tended to use CD ROMs to distribute software and for large data files, such as encyclopaedias
• Data rich systems are more likely to be DVDs than CDs as they provide greater storage capacity

Question 8

What does R mean (optical disks)?

Answer 8

It indicates read only and these discs only allow data to be written once, and then it cannot be altered. Although the disc may be written many times until the capacity is full

-This may be a more appropriate storage media for archive as it eliminates the possibility of content being accidental erased

Question 9

What is a DVD RAM disc?

Answer 9

This is very much like the disc RW but data are stored in a different way, which means:

• the surface can be written to far more often than the surface of a DVD RW
• Access and reading time is much faster
• Reading and writing can take place simultaneously

Question 10

What is a Blu-ray Disc?

Answer 10

This is an optical storage media which has a much larger storage capacity than any other optical storage media, while at the same time being able to provide high speed data transfers

Question 11

What is a buffer?

Answer 11

This is a small amount of fast memory used as a temporary store.

• The processor can send data to the buffer, or receive data from the buffer very quickly.
• If there is more data than will fit the in the buffer, an interrupt is sent to the processor
• Every device has a buffer

Question 12

Hat is an interrupt?

Answer 12

This is an electronic signal sent to the processor, requesting the CPUs attention.

-any hardware device can send an interrupt

Question 13

What is the keyboards job?

Answer 13

To use keys to generate different character codes that the computer recognises and is within the character set

• Keyboards are the most common form of input device to a system because they are universally available and understood
• Natural or ergonomic keyboards have been developed to with a curve to make keyboards more comfortable to use

Question 14

What is a concept keyboard?

Answer 14

This is a touch sensitive keyboard, which has keys as part of a continuous surface which has pressure sensitive areas.

• The concept keyboards are programmed so that the individual keys represent things within an application software, such as the concept keys used in fast food restaurants to input orders
• This keyboard is less prone to damage and is well suited to a greasy environment

Question 15

What is a MIDI keyboard?

Answer 15

This is a musical instrument digital interface keyboard. It is normally arranged like a piano keyboard

Question 16

What does a mouse do?

Answer 16

A mouse is designed to be used as a pointer on a screen. It is helpful as it mimics the human action of pointing.

• It serves two purposes, to provide an analogue input from physical movement and a digital input from the mouse button
• There are also other variations that have been developed, such as track balls and touch pads that serve the same purpose

Question 17

What does a bar code reader do?

Answer 17

This is a scanner that reads laser light reflections from dark and light lines of varying thickness. The pair of lines make up a code that can be converted into a number

• When a barcode is scanned, the level of reflected lines light is captured as an electronic signal and converted to a digital reading
• Barcodes can be easily misread, therefore the check digit is there to ensure that the barcode has been read properly

Question 18

What does an optical character reader do?

Answer 18

This is a device that can read and distinguish the different characters in a given character set. This is done by reading and comparing the shape of the characters to that of the ones in the character set

Question 19

What is an optical mark reader?

Answer 19

This is a device that can recognise the presence of a mark on a sheet of paper. It’s position is scanned and converted to a digital reading

Question 20

What is the main advantage of both OCR and OMR ?

Answer 20

Data can be input to a computer system without having to be transcribed, thereby reducing the number of errors at the data capture stage

Question 21

What is a scanner?

Answer 21

This is a device that converts a document into pixels. The largest the number of pixels, or the smaller each individual pixel, the better the definition of the final picture

Question 22

What is a graphic tablet?

Answer 22

This is a flat glass surface on which the user can draw with a special pen. The tablet works by sensing where the pen is pointing and converts the movements of the pen to a digital reading that is interpreted by the software

Question 23

What are the uses of a microphone?

Answer 23

A micro phone can can be used to input sound into a computer. The sound can be used to provide an audio commentary for a slides how or they can be converted to text.

• An advantage of speaking into the computer is that input is more intuitive than typing at a standard keyboard
• Software on a computer can convert the audio of the spoken word into digital form for use in a word processor.
• The disadvantage is that the software used to translate the spoken word into text can be unreliable

Question 24

Why might a screen require more resolution?

Answer 24

Screens are categorised by the number of pixels displayed. This is known as screen resolution and the more pixels there are, the better the screen resolution

-A computer system running a modern games software needs high definition colour to produce a satisfactory picture. A high screen resolution is required for this

Question 25

What is a touch screen?

Answer 25

This is a screen device that acts as both an input device and an output device. It can output sound or output through displaying options. It can sense where the users pointing and can report the position the processor

-Touch screens are particularly useful in situations where a keyboard isn’t appropriate

Question 26

What is a printer?

Answer 26

This is a device that provides the user with a permanent, printed output from the system, also known as a hard copy

Question 27

What is a dot matrix printer?

Answer 27

This is a type of printer, it is slow by modern standards and the output is of poor quality. The output is produced by using a pin head made up of a matrix pin

-A carbon strip lies between the print head and the paper. Characters are produced by striking pins against the carbon strip

Question 28

What is an inkjet printer?

Answer 28

This is a printer that produces hard copy’s by spraying coloured ink onto the paper. The print head travels across the page a line at a time, in a similar way to the dot matrix printer.

• The ink reservoir is heated and it vaporises droplets of ink, which then forces small ink blobs into the paper
• Reasonable cost

Question 29

What is a laser printer?

Answer 29

This is a type of printer which produces very high quality output at high speeds and relatively low costs.

-It’s typical applications are:
An office environment in which the laser printer is used for general office administration

A school network where several network users have access to a shared printer

Question 30

How does a laser printer work?

Answer 30

• A print drum is negatively charged. The printer generates a bitmap image of the page and a laser beam shone onto the rotating drum.
• The laser creates an electro static charge which attracts negatively charged toner from the laser toner cartridge. The toner is fused onto the paper page with a heated roller

Question 31

How do plotters work?

Answer 31

The paper is placed on the flat surface and a set of pens move above it under control of the software. Plotters are used for applications that draw lines and geometric designs rather than characters.

-They tend to be used for drawing blue prints

Question 32

What factors must be taken into account when choosing a peripheral device?

Answer 32

• What people are going to use the application, age or class. Their ability with the computer systems and understanding of the software. If they have physical disabilities
• Under what circumstances will the system be used? If the input and output devices are to be used in the open air, then the environment will dictate the restrictions
• What software is being used? This dictates the type of input required and the type of output that is produced. It also has an influence on the peripherals that are suitable for the input and output

Question 33

What is pilot running?

Answer 33

this is when key parts of the new system are run alongside the old system until it is considered that they have been fully tested.

Question 34

What is parallel running?

Answer 34

Until the system can be considered fault free, the old and new sips stem are run side by side, both doing the same processing.

• It allows results to be compared to ensure that there are no problems with the new system. It is thought of as the safer option
• It is expensive as they need to run everything twice

Question 35

What is direct changeover?

Answer 35

This is when the old system is removed and the live new system replaces it completely and immediately

Question 36

What is phased implementation?

Answer 36

This is when parts a system are replaced while the other remain covered by the old system. This allows some testing and staff training to take place