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
2
Q
what does the CIR do
A
register that hold the instruction currently being executed
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
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
5
Q
what does the ALU do
A
performs all the mathematical calculations and logical operations in the CPU
6
Q
what does the MDR do
A
holds the memory location of the data that needs to be accessed
7
Q
what does the program counter do
A
processor register that indicates where a computer is in its program sequence
8
Q
what do the buses do
A
connects all the internal components of a computer, such as CPU and memory, to the motherboard
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
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
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
12
Q
what is the instruction set
A
all the program commands available within a particular CPU
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
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
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
16
Q
examples of input devices
A
- keyboards
- touch screen
- voice input
- biometrics
- mouse
17
Q
examples of output devices
A
- monitors
- printers
- sound
- voice
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
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
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
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
voice input for control systems
allows the user to activate or control a wide range of home automation
- eg alexa
26
how is voice input used for dictation system
- users can write words by speaking them aloud
example - speaking to google in the search bar
27
what is a voice print recognition
creates a digital model of unique vocal characteristics and then compares those features to the voice presented
28
describe the fde cycle
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
the registers and devices that are going to be used in the fde cycle and what their role/purpose is
- 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
characteristics/advantages of RAM cache memory
- 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
how does cache work
- 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
describe 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
- 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
advantages of internet/web cache
- 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
advantage of harvard architecture
- 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
what are the advantages of 64 bit computers, increasing memory and using multicore processors
- 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
what is parallel processing
- 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
drawbacks of parallel processing
- 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
what is assembly language converted into machine code using
assembler
39
why do programmers use assembly language
- 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
disadvantages of assembly language
- 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
overview of external backing store
- 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
mechanical storage
- 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
solid state drives
- 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
what is word size
- 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
what is a hybrid drive
a storage drive that combines the large storage capacity of an HDD with the faster read/write speed of an SSD
46
what is the cheapest back store in order
- 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
what is the fastest backing store
- 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
describe disk fragmentation
- 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
what is data defragmentation
- 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
how does USB connect
- 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
how does bluetooth connect
- communicate using short range ultra-high frequency radio waves (electromagnetic waves with frequencies around 2.4 GH)
comp sci
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