AS2- Hardware, Compression and Digitisation

Question 1

What is the Control Unit

Answer 1

Sends control signals too other parts of CPU and computer system e.g. RAM, ALV AND I/O devices

Question 2

What does the Decoder do

Answer 2

Decoder will decode (understand) the instructions given to CPU
Co-ordinate the movement of data and instructions between CPU, RAM and devices

Question 3

What is the ALU

Answer 3

Arithmetic and Logical Unit
Carries out mathematical functions/ processors
e.g. Addition comparisons etc.
Carries out logical function such as Boolean and shifting

Question 4

What is the purpose of the Clock

Answer 4

Sends timing signals to the control units and ACU and other parts of CPU (“Like a Metronome”)
Its used to co-ordinate the actions of these components
…i.e. do things at the same time
… Synchronised

Question 5

What is the Programme Counter p.c.

Answer 5

Points at the next instruction to be processed
.. In RAM
Increments after each instruction is fetched into CIR
… or overwritten when branching or jumping

Question 6

What is the Memory Address Register Mar

Answer 6

Points at the location in RAM where data is being lead from or written to.

Question 7

What is the Current Instruction Register CIR

Answer 7

Adds the instruction that is currently being processed

Question 8

What is the Memory Data Register MDR

Answer 8

Holds the data that has just been read in or about to be written out.

Question 9

What is a Control Bus

Answer 9

The control units puts control signal onto the control bus i.e. control bus carries control signals
e.g. Read, Written, etc…

Question 10

What is the Address Bus

Answer 10

The location in RAM of data or instruction that is currently being accessed (read/written) (Address on PC or MAR)

Question 11

What is the Data Bus

Answer 11

Carries the actual data that is being transferred between CPU / Memory / Device

Question 12

Explain what the term Fetch means

Answer 12

Instructions + data fetched from memory and brought to cpu for processing
P.C. (Points at location of next instruction) address carried on address bus
Control bus will carry a read command (fetch) and the instruction is transferred to the CIR inside the CPU
CIR inside the CPU. Along the data bus.
PC is then incremented

Question 13

Explain what the term Data Fetch means

Answer 13

MAR (Points at location of data to be fetched) address carried on Address Bus
Control bus will carry read command fetch and the data is transferred to the MDR inside the CPU, along the data bus.

Question 14

Explain what the term Decode means

Answer 14

The CPU needs to understand the instruction in the CIR
There is a special part of the C.V.
Called the Decoder, which looks at the instruction in the CIR and decides which circuits on the CPU will carry out the instruction

Question 15

Explain what the term Execute means

Answer 15

After the instruction is decoded, the CV now understands what needs to be done. The control unit will then carry out the instruction itself or pass the instruction to the ALU if it is an arithmetic or logical task

Question 16

What does WIMP stand for and explain

Answer 16

Windows-
Containers for each application or open file.
Multiple windows/ containers open simultaneously
Word, system-explorer, internet explorer
Icons-
Pictorial representation of an item/object within the computer system
e.g. File, application, tool
Click right click to form operations such as open…
Menus-
List of options
Usually as drop down or pop up lists
Can be selected by a pointer or navigation buttons
Instigate functionality/ tools e.g. file - save - edit etc.
Pointers-
Used to track mouse position on screen
Used to select menu options and icons
Can give additional feedback to the user e.g. Finger pointer for hyperlink

Question 17

What is Command Line

Answer 17

The user must input text commands to interface at cursor
Commands must follow a very specific structure (syntax)
Commands must be ‘known’ to system in order to function
Prompt will let user know there location in fill structure
Pipeline more instructions
Powerful instructions compared to WIMP

Question 18

What is a form dialogue

Answer 18

It is a pop up box with information for the end user. It can have different options to progress e.g error messages with options to close, go back etc
User completes an action through an action through a series of dialogue boxes, when user inputs data or selects options at each stage e.g. wizard

Question 19

Why do we compress files

Answer 19

It reduces file size, which reduces data
saves on storage
Faster upload and download speed

Question 20

What is zipping

Answer 20

Uses L2W compression
,,,,Looks for patterns in the data
…. replaces the patterns with single characters

Question 21

Describe and Explain GIF

Answer 21

Graphic Interleave Format
8 bit format = max 256 colours, Animated Version
… Small file size
… Limited Quality
… Suitable for Clipart type images

Question 22

Describe and explain JPEG

Answer 22

Joint Photographic Expert Group
24 bits for colour = 16.7 million
… Larger than GIF
Uses run length compression to reduce file size by declaring some colour once when in a row of pixels
They make use of the fact that the human eye cannot detect small differences in colour
…. Group similar colours together into 1 colour
…. Increase the number/size of pixel colour runs.
Vary on the grouping sizes to further reduce the file size.

Question 23

Describe and explain Bitmap

Answer 23

Grid of pixels e.g. 640 x 480
Each pixel is assigned a colour
… Make up the image
. bmp, JPEG, GIF are all bitmap types

Question 24

Describe and explain .bmp

Answer 24

Up to 32 bit per pixel
4.3 billion colours
Each pixel has an individual colour definition
.. No compression

Question 25

Describe and explain lossless

Answer 25

-Reduction in file size
-But the original data can be fully recovered
… No data loss
… No loss in quality

Question 26

Describe and explain Lossy

Answer 26

There is a loss of data
Reduction in quality
Balanced against the larger reduction in file size and purpose of file

Question 27

How can sound be digitised

Answer 27

Regular readings are taken on the amplitude of the sound waves ….. turned into binary numbers
…..Called sampling
….. Higher sample rates = More readings = More data to be stored = Larger file size = Higher quality

Question 28

Describe and Explain Bit Depth

Answer 28

Number of bits used to represent each sample value
…. scale on y axis
Larger scale, the more accurate each sample value can be
Larger scale = More bits per same = More data = Larger File = Better quality

Question 29

Explain WAV format

Answer 29

Sound wave file
Take regular samples of amplitude of wave
Stored as values
Vary bit depth

Question 30

Describe and Explain mpeg

Answer 30

Moving pictures expert group
Layer 3 aka mp3
Removes any sounds that are too raw or to high pitch for human ears to detect
Looks for repetition in sound file
Stores repeated sound once only

Question 31

What is a mpeg video format

Answer 31

It is a container file
It stores multiple files inside 1 container
Multiple pictures (illusion of moving pictures)
Sound file (mp3)
Other code for synchronising

It uses delta compression which applies to the series of images
… doesn’t necessarily load full image each time
… Only overlay the parts of the image that are different from image before
i.e. small images are stored = less data
Regular full images for refresh

Question 32

How is text imputed into a computer system

Answer 32

Hardware:
Keyboard 
Mouse on screen
Touchscreen 
Button press
…. stream of bits
…. represents ASCII characters

Question 33

What is Digitisation

Answer 33

Process of turning real world analogue values in discrete binary numbers for storage processing
… ADT hardware analogue to digital converter
Binary numbers = Digital
Digitisation is needed as computers are digital devices and can only work on digital data

Question 34

How is sound digitise by using hardware

Answer 34

Microphone - Turn sound waves into voltage

Soundboard : Turns voltage into a set of binary values

Question 35

How are images digitised

Answer 35

Digital Camera
Light enters camera
Lens focus light on 'sensor'
… Array of individual light sensors detect colour light
… One sensor per pixel