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GCSE Computing > 3.4 Computer Systems > Flashcards

3.4 Computer Systems Flashcards

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1
Q

Definitions of hardware and software:

What is the relationship between them?

A

Hardware: physical stuff that make up the computer system
(CPU, motherboard, monitor, printer)

Software: programs a computer system runs
(Application software, system software)

Work together to process data/complete tasks

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2
Q

Name the 3 logic gates and their shapes:

A 
NOT = triangle
AND = semi-circle
OR = rocket
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3
Q

What is system software?
Vs
What is application software?

A

System Software: software designed to run and maintain a computer system
(OS = Operating System, Utility software)

Application software: programs that help the user perform specific tasks
(Word processors, web browsers, games)

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4
Q

Main functions of Operating systems (OS):

A

manages hardware and runs software

Main functions:

  • communicate with input/output devices via device drivers
  • provide platform for applications to run on & a user interface
  • control memory management & allocation
  • organise CPU & its processing tasks
  • deal with file management & disk management
  • manage system security & user accounts
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5
Q

Explain the Von Neumann Architecture:

What does each part do?

A
  • describes a system where CPU runs programs stored in memory
  • programs consist of instructions/data stored in memory addresses
  • CU controls flow of data & keeps track of memory address of instruction for next cycle
  • memory holds program instructions/data
  • ALU gets data from CU and registers, performs operation on it & sends output back to registers
  • registers hold any data/instructions/memory addresses about to be used by CPU, specific registers for different tasks
  • input/output device
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6
Q

What are the major components of a CPU? (Central Processing Unit):

A
  • Arithmetic Logic Unit
  • Control Unit
  • Clock
  • Bus
  • Cache
  • registers
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7
Q

What does the arithmetic logic unit (ALU) do?

A
  • complete simple addition/subtraction
  • compares sizes of numbers
  • can do multiplication/division using repeated addition/subtraction
  • performs logic operations and binary shifts
  • registers used to store immediate results if calculations
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8
Q

What does the Control Unit (CU) do?

A
  • manages fetching, decoding and execution of program instructions (fetch-decode-execute cycle)
  • controls flow of data inside CPU (to registers, ALU, cache)
  • controls flow of data outside CPU (to main memory, input/output devices)
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9
Q

What does the clock do?

A
  • sends out an electrical signal/pulses that continually cycles between 1 and 0, usually at constant rate
  • signal used to synchronise when instructions will be carried out
  • clock speed = no. of clock cycles executed by CPU per second
  • measured in GHz
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10
Q

What are Buses, what do they do?

A
  • collection of wires used to transmit data between components of CPU, and to other parts of computer system
  • processor may have separate buses for carrying data, instructions and memory addresses
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11
Q

What is Cache? What does it do?

A
  • very fast memory in CPU
  • stores regularly used data so CPU can access it quickly
  • very low capacity & expensive
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12
Q

What are registers? What do they do?

A

Registers are small amounts of high speed memory contained within the CPU. They are used by the processor to store small amounts of data that are needed during processing

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13
Q

5 most common registers: (in vonn Neumann)

A
  • program counter
  • memory address register (MAR)
  • memory data register (MDR)
  • current instruction register (CIR)
  • accumulator (ACC)
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14
Q

What affects the performance of the CPU?

A
  • clock speed
  • no. of processor cores
  • cache size
  • cache type
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15
Q

What does clock speed do?

What is the affect of clock speed on the CPU?

A
  • determines the no. of instructions a single core processor can carry out per second
  • some CPUs can be ‘overclocked’ to make them run at a higher clock speed than factory set rate. But CPUs can overheat, causing crashes or permanent damage) so high performance cooling systems often needed
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16
Q

What is the affect of No. of processor cores on the CPU?

A
  • more cores a CPU has = more instructions it can carry out at once = faster process of data
    (Each core processes data independently of the rest)
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17
Q

What is the effect of cache size on the CPU

A
  • larger CPU cache gives CPU faster access to more data it needs to process
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18
Q

What is the effect of cache type on the CPU?

A
  • there are three levels of cache memory
  • higher level = holds more but slower
  • cache speed based on how far it is from CPU (L1 is on CPU, L3 is on motherboard)
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19
Q

What are embedded systems?
What are the properties of embedded systems?
Give some examples

A

= computer built into a device, dedicated systems

  • RAM and ROM on same chip as CPU to reduce space/cost
  • more ROM than RAM
  • norm no secondary storage
  • ROM stores all programs
  • control systems (monitor and control memory)

Eg. Dishwasher, calculator, microwaves, washing machines

20
Q

What are Non-embedded systems?
What is the memory type on them?
Give some examples

A

= general purpose (not dedicated)

  • RAM and ROM on motherboard
  • more RAM than ROM

Eg. Mobile phones, computers

21
Q

What are the advantages of embedded systems over non-embedded systems?

A
  • more efficient
  • easier to design
  • cheaper to produce
    (Dedicated to certain tasks)
22
Q

What is cloud storage?

A

Service where files can be uploaded via the internet to a remote server
(Usually stored on HDDs/SSDs)

23
Q

Advantages of cloud storage (compared to local storage)?

A
  • Users can access from any device
  • files can be shared/made public
  • easy to increase amount of storage available
  • no expensive hardware/IT staff needed
  • host provides security and backups for you
  • can be cheap if not much storage needed
24
Q

Disadvantages of cloud storage (compared to local storage)

A
  • need connection to internet
  • upload/download speed depends on bandwidth
  • depends on host for security & backups
  • can be vulnerable to hackers
  • unclear ownership of data
  • subscription fees for long term storage may be expensive
25
Q

Describe RAM (random access memory)

A

= main memory of computer

  • volatile (temporary) = needs power to retain data
  • data files/programs stored here when used
  • computer boots -> OS copied from secondary storage to RAM
  • when files transferred -> secondary storage to RAM
  • slower than CPU, faster than secondary storage
26
Q

Describe ROM (read only memory)

A
  • ROM chips use flash memory = non-volatile (not temporary)
  • only read, not written to
  • has instructions to boot up computer (BIOS - Basic Input Output System)
  • more small chip in motherboard
  • power on -> CPU reads instructions from ROM (CPU self checks & sets up computer)
  • can update BIOS
27
Q

What is the Main memory (primary storage)?

A
  • memory areas CPU can access directly
    Eg. CPU registers (MAR, MDR), cache, RAM, ROM
  • mostly volatile(except ROM)
  • fastest read/write speeds
28
Q

What is Secondary storage?

A
  • where all data stored when not in use
  • non-volatile
  • much slower than main memory (primary)

Eg. Magnetic hard drives, SSDs, CDs, SD cards

29
Q

Types of secondary storage:

A
  • solid state
  • optical
  • magnetic
30
Q

Explain the operation of Magnetic storage (HDDs = Hard Disk Drives)

A
  • HDDs = traditional internal storage in PCs/laptops
  • made up of stack of magnetised metal disks spinning at rate between 5400 and 15000 revolutions per minute
  • data stored magnetically in small areas(sectors) within circular tracks
  • read/write heads on moving arm used to access sectors on disks
31
Q

Other types of magnetic storage

A
  • magnetic tape

- floppy disks

32
Q

Advantages of magnetic storage (HDDs)

A
  • cheaper than SDD
  • higher capacity than SDD
  • longer read/write life (SDDs deteriorate after written certain no. of times
  • portable HDDs popular for backing up/transporting large amounts of data
  • long lasting
  • reliable
33
Q

Disadvantages of magnetic storage (HDDs):

A
  • noisy
  • not shock proof, can be damaged by large impacts
  • not as fast as SDD
  • contains moving parts = fragile
34
Q

Explain the operation of Solid state storage (SDDs - Solid State Drives/USB)

A
  • SDDs used for internal storage, no moving parts
  • most use a type of flash memory
  • uses semiconductor chips to store data.
35
Q

Advantages of Solid state storage (SDDs)

A
  • faster read/write times than HDD
  • quicker times for booting up/opening programs/files
  • don’t need defragmenting
  • shock-proof
  • silent
36
Q

Disadvantages of solid state storage (SDDs)

A
  • more expensive

- SDDs can only be written certain no. of times before they start to deteriorate = shorter read/write life

37
Q

Other types of flash storage:

A

-

38
Q

Explain the operation of optical discs/storage:(CDs, DVDs, Blu-Ray)

A
  • data stored as microscopic indentations on shiny surface of disc
  • data read by shining laser beam on surface and detecting changes in position of reflected beam

Comes in 3 forms

  • read-only
  • write-once
  • rewritable
39
Q

Advantages of Optical discs(CDs, DVDs, Blu-Ray)

A
  • very cheap (per GB)
  • portable
  • quite robust so wont be damages by water/shocks (but easily scratched)
40
Q

Average read/write speed of different types of secondary storage
(Fastest -> slowest)

A 
SDD
HDD
Magnetic tape
Memory/SD card
Optical disc
41
Q

Disadvantages of optical discs (CDs, DVDs, Blu-Ray)

A
  • streaming/downloading is easier nowadays
  • can’t compete with flash storage devices due to:
  • low capacity per disc
  • very slow read/write speeds
  • poor reliability of RW discs
42
Q 
Average cost (per GB) of different types of secondary storage
(Most expensive -> cheapest)
A 
SDD
Memory card
HDD
Optical disc
Magnetic tape
43
Q

Average capacity of different types of secondary storage

Highest -> lowest

A 
Magnetic tape
HDD
SDD
Memory card
Optical disc
44
Q

Fetch-decode-execute cycle

A

CPU read instructions stored in main memory and executes them:
Fetch:
- control unit reads memory address of next CPU instruction
- instruction stored copied from main memory to one of registers
-
Decode:
- instruction decoded by control unit
Execute:
- instruction is carried out
Eg. Data may be read from/written to main memory, calculation/logic operation (ALU), change address in CU, halt program

45
Q

Flash memory:

A
  • non-volatile memory
  • stores data in electric circuits by trapping electrons
  • used in USB sticks/SD cards/SSDs
46
Q

How much data can __ hold?

  • CDs
  • DVDs
  • Blu-Rays
A
  • CDs = 700 MB
  • DVDs = 4.7 GB
  • Blu-Rays = 25GB

GCSE Computing (8 decks)

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