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comp sci > 2.1 hardware > Flashcards

2.1 hardware Flashcards

1
Q

what are the components of the CPU

A
  • current instruction register
  • registers
  • control unit
  • arithmetic logic unit
  • memory data register
  • memory address register
  • program counter
  • buses
  • cache memory
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2
Q

what does the CIR do

A

register that hold the instruction currently being executed

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3
Q

what do the registers do

A

they are a small amount of fast access storage and are normally used for a specific purpose where data or control information is temporarily stored

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4
Q

what does the control unit do

A
  • directs the flow of instructions
  • coordinates the other parts of the CPU
  • generates clock ticks or controls the clock
  • to manage the execution of instructions
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5
Q

what does the ALU do

A

performs all the mathematical calculations and logical operations in the CPU

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6
Q

what does the MDR do

A

holds the memory location of the data that needs to be accessed

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7
Q

what does the program counter do

A

processor register that indicates where a computer is in its program sequence

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8
Q

what do the buses do

A

connects all the internal components of a computer, such as CPU and memory, to the motherboard

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9
Q

what does the address bus do

A

used to specify the address in memory where data will be read from or written to

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10
Q

what does the data bus do

A

this is used to transfer data from memory into the CPU or from the CPU back to memory

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11
Q

what does the control bus do

A

used to send control signals between parts of the computer

for example, it specifics whether the data is being written to or read from memory

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12
Q

what is the instruction set

A

all the program commands available within a particular CPU

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13
Q

what are the general purpose registers

A
  • used when a program instruction is being carried out to hold temporary values
  • may be used to hold the details of the instruction being carried out, an address to be accessed etc
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14
Q

RAM memory

A
  • random access memory - volatile ( data is lost if power is removed)
  • can hold program instructions and data
  • programs to be executed and first loaded from backing store before being run - this is because Ram 🐏 is much faster
  • one of these programs held in ram is the operating system
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15
Q

ROM memory

A
  • read only memory - no volatile (data remains when power is turned off)
  • holds a simple os (BIOS) burnt onto the chip at the time of manufacture
  • the BIOS runs a ‘bootstrap loader’ that looks for another os to load into RAM from backing store
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16
Q

examples of input devices

A
  • keyboards
  • touch screen
  • voice input
  • biometrics
  • mouse
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17
Q

examples of output devices

A
  • monitors
  • printers
  • sound
  • voice
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18
Q

advantages of speech recognition (speech input)

A
  • no need to be able to type
  • faster input
  • use over telephones
  • very useful for some disabled people
  • useful when using hands for driving
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19
Q

disadvantages of speech recognition (speech input)

A
  • keywords may become confused with input text ( eg, full stop, new paragraph)
  • background noise can cause problems
  • others may overhear what you are saying
  • can make for a noisy working environment
  • ambiguity
  • may not recognise proper nouns (names) or slang words
  • can be a slow input
  • accents
  • colds, speech impediments etc
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20
Q

advantages of speech synthesis (speech output)

A
  • computer able to read documents/e-books/emails
  • very useful for blind or partially sighted or people who cannot read
  • could be used via a telephone (eg. booking a cinema)
  • could be used to help learn how to pronounce foreign words
  • error information warnings (eg. lift doors closing)
  • no need to look at a screen, could be telling you information when eyes are occupied
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21
Q

disadvantages of speech synthesis (speech output)

A
  • can often be quicker to read it yourself
  • voice often sounds unnatural at the parts of words are joined together, lacks emphasis on particular words in sentences
22
Q

advantages of handwriting recognition

A
  • many people can write faster than they can type
  • no need to learn to type
  • feel more natural to some people
  • useful where not enough space for a key board (eg. on a handheld device)
23
Q

disadvantages of handwriting recognition

A
  • not always 100% accurate
  • some hand writing is very difficult to interpret
  • using the pen interface can sometimes feel unnatural
24
Q

interfaces for users with disabilities

A
  • 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
25
Q

voice input for control systems

A

allows the user to activate or control a wide range of home automation
- eg alexa

26
Q

how is voice input used for dictation system

A
  • users can write words by speaking them aloud
    example - speaking to google in the search bar
27
Q

what is a voice print recognition

A

creates a digital model of unique vocal characteristics and then compares those features to the voice presented

28
Q

describe the fde cycle

A

fetch:
- the program counter holds the address of the first item to be fetched in RAM
- the control unit moves this address into the MAR
- the address is sent from the MAR along the address bus to main memory
- the instruction at that address if found and returned along the data bus to the MDR
- at the same, the program counter is incremented by 1 to show that the address of the next instruction to be fetched
- the control unit loads the program instruction to the CIR from the MDR

decode:
- the instruction is decoded by the control unit so it knows which instruction to execute

execute:
- the instruction/command is executed

29
Q

the registers and devices that are going to be used in the fde cycle and what their role/purpose is

A
  • pc: an incrementing counter that keeps track of the memory address of which instruction is to be executed next
  • mar: the address in main memory that is currently being read from or written to
  • 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
  • cir: a temporary holding ground for the instruction that has just been fetched from memory
  • cu: decodes the program instruction in the cir, selecting machine resources such as data source register and a particular arithmetic operation, and coordinates activation of those resources
  • alu: performs mathematical and logical operations
30
Q

characteristics/advantages of RAM cache memory

A
  • small and 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 cache is full, the 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)
  • 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.
31
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 when it was accessed
  • therefore, if a memory location needs to be read by the CPU, it will get it from the cache if it is there rather than RAM which will be much faster
  • as large sections of program instructions are in loops, it is very common for the same address to be accessed multiple times, therefore, cache can make programs run faster
32
Q

describe disc cache

A
  • 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
  • keeps blocks of data in ram so that recently accessed blocks can be read more quickly again from ram than having to read from the slower hard disk
  • as ram is so much faster than disc, there is no need to use special more expensive memory for a disc cache
33
Q

advantages of internet/web cache

A
  • view previously viewed page to speed up viewing (as they are read from disc which is usually quicker than downloading them again)
  • storing ‘pre-fetched’ pages
  • storing pages in anticipation of not having internet access in future so pages can still be viewed
34
Q

advantage of harvard architecture

A
  • has separate instruction and data buses
  • this means that program instructions being fetched at the same time as the previous instruction being executed is reading/writing data in memory
  • this helps to increase processing speed
35
Q

what are the advantages of 64 bit computers, increasing memory and using multicore processors

A
  • a 64 bit system can access 2^64 memory addresses and is required to handle any amount of memory greater than 4GB
  • 64-bit multicore processors allow an increased number of calculations per second, which will make the system run faster and operate more efficiently
  • a 64 bit helps with multitasking, where users can easily switch between applications without noticeable delays
36
Q

what is parallel processing

A
  • the use of more than one processor or processor core to perform a single task so that many multiple calculations can be carried out simultaneously
  • programmers can take advantage of parallel processing to allow different lines of code to be carried out simultaneously across multiple processors or cores
  • particularly useful where large/complex calculations are being carried out (weather forecasting etc)
  • different parts of the program can be run at the same time and are identified by the programmer and allowed to run in their own thread
37
Q

drawbacks of parallel processing

A
  • difficult to write computer programs so that different portions can be run at the same time without interfering with each other
  • due to its complexity, the potential benefits of parallel processing are rarely fulfilled
  • there are always parts of a program where the parallel tasks come together and the code can only be executed by one processor
38
Q

what is assembly language converted into machine code using

A

assembler

39
Q

why do programmers use assembly language

A
  • ideal when the execution speed is critical (eg. boot strap loader)
  • more efficient than high level language programs
  • require less time for translation into machine code
  • generally results in smaller executable programs
40
Q

disadvantages of assembly language

A
  • is machine dependent: a program written for one computer might not run on other computers with different hardware configuration
  • it is long and tedious to write initially
  • your code can be fairly difficult to understand and modify (eg. maintain)
41
Q

overview of external backing store

A
  • forms of non volatile storage
  • stores data to be used time and time again often over long periods
  • usually slower and cheaper than RAM
  • can be sometimes used to backup data to keep it safe
  • examples: files, programs, documents, photos, music
42
Q

mechanical storage

A
  • tend to be slower access speeds but are also cheaper, in the case of hard disks they can have very large amounts of storage

hard disks:
- more likely to be damaged if dropped due to moving parts
- generally have a long life span
- will sometimes require defragmentation

  • CDROM/ DVD/ BLURAY have small capacities
  • magnetic tape has larger capacity, they are still sometimes used for backup purposes because they are cheap and store a lot of data
  • they are relatively fast when writing data but slow for recovering but can be easily stored in a safe or transferred for offsite backup
43
Q

solid state drives

A
  • solid state and flash memory is faster but more expensive than hard disk
  • SSD are direct replacements for hard-drives but use more expensive flash memory, they tend to be less reliable over time but are increasingly used in modern computers to improve speed
  • made up of NAND flash which is shock resistant
  • no moving parts so tend to be more power efficient
  • tend to be lightter, quieter (near silent), use less power and run cooler than traditional hard drives
  • do not require defragmentation
44
Q

what is word size

A
  • the number of bits that the processor can deal with in a single operation
  • not a fixed measure and depends on the processor being used
  • eg. a 64 bit PC has a word size of 64 bits (8 bytes)
45
Q

what is a hybrid drive

A

a storage drive that combines the large storage capacity of an HDD with the faster read/write speed of an SSD

46
Q

what is the cheapest back store in order

A
  • hard disk
  • SSD
  • flash memory
  • hard disk is by far the cheapest, the drives are reliable but are more likely to be damaged if dropped
  • SSDs are replacements for hard drives but are more expensive, they are less likely to be damaged and are silent
47
Q

what is the fastest backing store

A
  • SSD
    -flash memory
  • HHD
  • flash memory are small and can be carried around easily, sent through the post etc, their speed is limited by the USB port speed, though newer USB 4 drives and later are faster
48
Q

describe disk fragmentation

A
  • when all but the smallest files are saved to 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 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 os 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
49
Q

what is data defragmentation

A
  • when necessary, an os will automatically run a defragmentation routine which moves the blocks around to make sure that the files take up a contiguous set of blocks
  • SSD drives do not require defragmentation as there are no mechanical read/write heads to move, therefore, fragmentation does not slow down the operation
50
Q

how does USB connect

A
  • the types of cables and connectors used to connect these many types of external devices to computers
  • eg. USB ports and cables are used to connect hardware such as printers, scanners, keyboards, mice and flash drives
51
Q

how does bluetooth connect

A
  • communicate using short range ultra-high frequency radio waves (electromagnetic waves with frequencies around 2.4 GH)

comp sci (11 decks)

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