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Computer Science > Hardware > Flashcards

Hardware Flashcards

1
Q

Name the hardware elements of a computer

A

Input Devices, Processor, Output Devices, RAM Cache Memory, RAM, ROM, External/Backing store

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2
Q

What is RAM?

A

RAM (Random Access Memory) is memory which holds program instructions (e.g. word processor, games) and data (the document being edited, the score of a game etc.)

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3
Q

What happens to RAM when power is removed?

A

RAM is volatile meaning data will be lost if power is removed.

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4
Q

What happens to programs in RAM to be executed?

A

They are first loaded from backing store (e.g. disk) before being ran. This is because RAM is much faster (and more expensive)

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5
Q

Name one of the programs held in RAM

A

Operating System

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6
Q

What does ROM do?

A

ROM holds a simple operating system (BIOS) ‘burnt’ onto the chip at the time of manufacture.

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7
Q

What does the BIOS do?

A

BIOS (basic input output system) is a simple operating system burnt onto ROM at the time of manufacture.

The BIOS runs a ‘bootstrap loader’ that looks for another operating system (e.g. Windows, Linux) to load into RAM from backing store.

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8
Q

What happens to ROM when power is removed?

A

ROM is non-volatile so data will remain when power is removed

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9
Q

Draw the Von Neumann architecture with names on each component.

A

Check if correct slide 4

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10
Q

What is the CPU and what does it do?

A

The CPU is the Central Processing Unit.

It controls the transmission of data to and from main memory. Processes the data in memory. Controls the transfer of data between input, output and main memory.

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11
Q

Name the components of a CPU and what each of them do.

A

Control Unit - Fetches each instruction in sequence from memory, decodes and synchronises it before executing it by sending control signals to other parts of the computer.

Arithmetic Logic Unit (ALU) - Carries out the processing and manipulation of data which normally consists of arithmetic operations (addition, multiplication, etc.) or logical comparisons (AND, OR, XOR, etc.)

General Purpose Registers - Temporary memory locations within the CPU. Used when a program instruction is being carried out to hold temporary values.

Instruction Set - all the program commands available within a particular CPU.

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12
Q

Name all the Special Registers and what they do

A

MAR (Memory Address Register) - Holds the address of the memory location currently being accessed.

MDR (Memory Data Register) - Holds the data read from (or to be written to) memory

PC (Program Counter) - The address of the next program instruction to be read from memory.

CIR (Current Instruction Register) - The instruction most recently fetched from memory.

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13
Q

What is a bus?

A

Buses are collections of wires inside the computer which transmit information between the components and also to input/output devices. There are three different bus types.

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14
Q

Name the three different buses and what they do

A

Address bus - Used to specify the address in memory where data will be read from or written to.

Data bus - This is used to transfer data from memory into the CPU (e.g. a program instruction or an item of data) or from CPU back to memory.

Control Bus - Used to send control signals between parts of the computer. One key example is it specifies whether the data is being written to or read from memory.

slides 8 and 9 for examples of read/write of the buses.

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15
Q

Give examples of an input device

A

Keyboards, touch screen, voice input, biometrics, mouse, joystick, pen/stylus input, touchpad.

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16
Q

Give examples of an output device

A

Monitors, printers, sound, voice, control (e.g. switching on heating, opening curtains)

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17
Q

What are the advantages of speech recognition (speech input)?

A
  • No need to type
  • Faster input as most people can speak faster than they can type
  • Useful for some people with disabilities
  • Useful when hands are occupied doing another task
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18
Q

What are the disadvantages of speech recognition (speech input)?

A
  • Background noise can cause problems
  • People overhear what you are saying
  • Can make a noisy work environment
  • May take time for the system to learn the users accent
  • Could misunderstand people with colds, speech impediments etc.
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19
Q

What are the advantages of Speech Synthesis (speech Output)?

A
  • Computer able to read documents, books etc.
  • Useful for partially sighted/blind people or people who cannot read
  • Could be used to learn pronunciation of words
  • Information warnings (e.g. lift doors closing)
  • No need to look at screen (useful for Satnav)
20
Q

What are the Disadvantages of Speech Synthesis (speech Output)?

A
  • Can often be quicker to read yourself

- The computer generated voice could sound unnatural and could emphasise certain words wrong.

21
Q

What are the advantages of Handwriting Recognition?

A
  • Many people can write faster than they can type
  • No need to learn to type
  • Useful when there is limited space for a keyboard e.g. handheld devices
22
Q

What are the disadvantages of Handwriting Recognition?

A
  • Not always 100% accurate
  • Some handwriting is very difficult to interpret
  • The pen interface may feel unnatural e.g. slippy surface
23
Q

What interfaces can be used for people with disabilities?

A 
Depending on the disability:
Speech Recognition;
Foot controlled keyboard/mouse;
Head/eye movement detector;
Oversized keyboard;
Head stalk to press keys;
Braille key overlays;
Screen readers (speech synthesis);
Large/clear fonts;
Clear colour contrasts;
Braille output.
24
Q

Name all of the registers/devices that are going to be used in the Fetch execute cycle

A

Program Counter (PC) - an incrementing counter that keeps track of the memory address of which instruction is to be executed next…

Memory Address Register (MAR) - the address in main memory that is currently being read or written

Memory Data Register (MDR) - a two-way register that holds data fetched from memory (and ready for the CPU to process) or data waiting to be stored in memory

Current Instruction register (CIR) - a temporary holding ground for the instruction that has just been fetched from memory

Control Unit (CU) - decodes the program instruction in the CIR, selecting machine resources such as a data source register and a particular arithmetic operation, and coordinates activation of those resources

Arithmetic logic unit (ALU) - performs mathematical and logical operations

25
Q

Summarise the fetch decode execute cycle.

A
  1. PC holds the address of the first program instruction
    Fetch
  2. Copy value in PC intro the MAR
  3. Control Bus is set to Read
  4. The data (instruction) in the address specified in the MAR is fetched into MDR
  5. As the MDR holds an instruction it is copied into the CIR
  6. The PC is incremented (has 1 added to it)
    Decode
  7. The instruction is decoded by the control unit so it knows which instruction it needs to execute
    Execute
  8. The instruction/command is executed
  9. Go back to step 2

Try fetch decode cycle on slide 30

26
Q

What is RAM Cache Memory?

A

Cache is small, extremely fast memory

Placed near or on the processor.

Data and instructions that are used regularly are stored in cache and retrieved by the processor when necessary.

When the cache is full least recently used data is discarded.

Caching systems will try to predict the next instructions to be accessed and pre-fetch them into the cache.

Algorithms try to avoid a cache miss (when data has to be fetched from main memory rather than cache).

Cache memory attempts to solve the “Von Neumann Bottleneck”. CPUs are so fast that data from RAM can’t be fetched quickly enough to keep them occupied. Cache memory helps with this by providing data more quickly.

27
Q

How does cache work?

A

Data being read from RAM is copied into the cache - it records the address the data came from, the data itself and a timestamp of when it was accessed.

28
Q

What does disk cache do?

A

This works in a similar way to RAM cache by keeping copies of blocks of data in RAM so that recently accessed blocks can be read more quickly again from RAM rather than having to read from the slower hard disk.

As RAM is so much faster than Disk, there is no need to use special more expensive cache memory for a disk cache.

29
Q

What is a problem with the Von Neumann architecture?

A

The program instructions and data are accessed via the same data and address buses.

That’s why modern processors use a modified Harvard architecture which has separate instruction and data buses.

30
Q

What is parallel processing?

A

Parallel processing is the use of more than one processor (CPU) or processor core to perform a single task (execute a program).

31
Q

When is parallel processing useful?

A

Parallel processing is useful where large/complex calculations are being carried out e.g. image processing, weather forecasting etc.

32
Q

What is a compiler

A

A compiler converts the whole program into machine code before it is run.

33
Q

What is assembly language?

A

It is an alternative to machine language. Instead of using binary numbers for instructions, assembly language uses short words that are known as mnemonics.

34
Q

Name the basic assembly language commands and what they do

A
  • LOAD R, X: Load
  • STOR R, X: Store
  • ADD: Add
  • SUB: Subtract
  • JUMP: Program jumps to address X
  • COMP: Compares registers

BLE X: jumps to address x based on the previous comparison if less than or equal

BNE X: Program jumps to address X based on the previous comparison if not equal.

35
Q

Relocatable Code

A

Programs that can be run from any memory location

36
Q

What is a linker?

A

another program that will replace the labels with the appropriate memory addresses

37
Q

Why would programmers not use assembly language?

A
  • machine dependant. (meaning that if it is written for one computer it might not work on another)
  • long and tedious to write.
  • code very difficult to maintain
38
Q

why do programmers use assembly language?

A
  • Ideal when execution speed is critical (e.g. boot strap loader)
  • More efficient than high level language programs
  • Requires less time for translation into machine code as assembly language is a 1 to 1 match to machine code
39
Q

What is disk fragmentation?

A

When all but the smallest files are saved to (mechanical) hard-disk they will usually take up a number of disk blocks

Fragmentation occurs when the file system cannot or will not allocate enough contiguous space to store a complete file as a unit, but instead puts parts of it in gaps between existing files.

Usually those gaps exist because they formerly held a file that the operating system has subsequently deleted.

It will be slower to open a fragmented file as the read/write head on the disk drive has to move to load each part from a different track and mechanical movement slows the operation down.

40
Q

What is disk fragmentation?

A

When all but the smallest files are saved to (mechanical) hard-disk they will usually take up a number of disk blocks

Fragmentation occurs when the file system cannot or will not allocate enough contiguous (next to eachother) space to store a complete file as a unit, but instead puts parts of it in gaps between existing files.

Usually those gaps exist because they formerly held a file that the operating system has subsequently deleted.

It will be slower to open a fragmented file as the read/write head on the disk drive has to move to load each part from a different track and mechanical movement slows the operation down.

41
Q

What is disk defragmentation?

A

-When necessary an operating system will automatically run a defragmentation routine which moves the blocks around to make sure that the files take up a contiguous (next to eachother) set of blocks.

slide 66 for before and after defragmentation

42
Q

What are the two traditional types of cache memory?

A

RAM cache and disk cache

43
Q

What is RAM cache?

A

RAM cache is memory between the CPU and main memory where sections of data and/or programs are stored

44
Q

What is disc cache

A

Disc cache is a section of main memory between the cpu and disc where data recently read from disc or about to be written to disc is temporarily stored (before being transferred to RAM)

45
Q

What is amdahls law

A

Parallel processing time = time using a single processor system(fraction of processing which must be linear + fraction which can be run in parallel / number of processors)

Computer Science (6 decks)

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