AS2- Hardware, Compression and Digitisation Flashcards
What is the Control Unit
Sends control signals too other parts of CPU and computer system e.g. RAM, ALV AND I/O devices
What does the Decoder do
Decoder will decode (understand) the instructions given to CPU
Co-ordinate the movement of data and instructions between CPU, RAM and devices
What is the ALU
Arithmetic and Logical Unit
Carries out mathematical functions/ processors
e.g. Addition comparisons etc.
Carries out logical function such as Boolean and shifting
What is the purpose of the Clock
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
What is the Programme Counter p.c.
Points at the next instruction to be processed
.. In RAM
Increments after each instruction is fetched into CIR
… or overwritten when branching or jumping
What is the Memory Address Register Mar
Points at the location in RAM where data is being lead from or written to.
What is the Current Instruction Register CIR
Adds the instruction that is currently being processed
What is the Memory Data Register MDR
Holds the data that has just been read in or about to be written out.
What is a Control Bus
The control units puts control signal onto the control bus i.e. control bus carries control signals
e.g. Read, Written, etc…
What is the Address Bus
The location in RAM of data or instruction that is currently being accessed (read/written) (Address on PC or MAR)
What is the Data Bus
Carries the actual data that is being transferred between CPU / Memory / Device
Explain what the term Fetch means
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
Explain what the term Data Fetch means
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.
Explain what the term Decode means
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
Explain what the term Execute means
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
What does WIMP stand for and explain
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
What is Command Line
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
What is a form dialogue
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
Why do we compress files
It reduces file size, which reduces data
saves on storage
Faster upload and download speed
What is zipping
Uses L2W compression
,,,,Looks for patterns in the data
…. replaces the patterns with single characters
Describe and Explain GIF
Graphic Interleave Format 8 bit format = max 256 colours, Animated Version … Small file size … Limited Quality … Suitable for Clipart type images
Describe and explain JPEG
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.
Describe and explain Bitmap
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
Describe and explain .bmp
Up to 32 bit per pixel
4.3 billion colours
Each pixel has an individual colour definition
.. No compression
