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Computer Science > Unit 4 Computer Systems > Flashcards

Unit 4 Computer Systems Flashcards

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1
Q

Binary logic - AND Gate

A
  • If both inputs are 1 (True) then the output is 1 (True)
  • Otherwise the output is 0 (False)
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2
Q

Binary logic - OR Gate

A
  • If either input is 1 (True) then the output is 1 (True)
  • Otherwise the output is 0 (False)
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3
Q

Binary logic - NOT Gate

A
  • If the input is 1 (True) then the output is 0 (False)
  • If the input is 0 (False) then the output is 1 (True)
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4
Q

Binary logic - XOR Gate

A
  • If just one input is 1 (True) then the output is 1 (True)
  • Otherwise the output is 0 (False)
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5
Q

What does a dot symbol placed at the end of any logic gate mean?

A

Acts as both the gate and a NOT gate combined.

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6
Q

Explain the definition of hardware.

A

The physical components that make up a computer system.

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7
Q

Explain the definition of software.

A
  • Software is the non-physical programs that are stored by and run on a computer system
  • Software makes use of physical hardware components and devices as the way of: taking inputs from users, outputting information to users, storing information
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8
Q

What is an operating system?

A

A group of programs that is essential for managing the computer’s resources. They are responsible for managing: processor(s), memory, input/output devices, applications, security

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9
Q

Explain the term multi-tasking.

A

Where an operating system manages many tasks happening at the same time

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10
Q

What are interrupts?

A
  • Signals sent to the CPU by external devices to indicate an event that needs immediate attention
  • They tell the CPU to suspend its current activities and execute appropriate instructions
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11
Q

What is the difference between hardware and software interrupts and give examples?

A
  • Hardware interrupts are generated by hardware devices e.g. printer run out of paper
  • Software interrupts are generated by programs e.g. a divide by zero error will cause an error message to be displayed
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12
Q

Describe the process of memory management.

A
  • To run a program, a computer must copy the program from storage into main memory
  • Data used by the program is copied into main memory
  • The operating system keeps a record of where each program and its data is located
  • The operating system will make sure not to overwrite existing programs and data
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13
Q

Give some examples of peripheral devices.

A

Mice, keyboard, printers, displays, digital cameras, and graphics tablets

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14
Q

What is a device driver?

A
  • A program that controls peripheral devices.
  • Each device communicates with the OS via its own driver
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15
Q

Explain the process of operating system application management.

A
  • The operating system (OS) provides graphical user interface (GUI) features such as windows, maximize, minimize, resize
  • When an application is opened the OS will copy the program into RAM and allocate an area of RAM for the program to use
  • When an application is closed the operating system will make sure that it is removed from RAM
  • The operating system may also be responsible for installing and updating applications
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16
Q

What security features do operating systems often contain?

A
  • User management with usernames and passwords
  • Access rights to files, programs and services
  • Encryption of hard drives and removable media
  • Memory protection : prevention of programs being able to view or overwrite other programs stored in the RAM
  • Security updates are automatically downloaded and installed
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17
Q

What is utility software?

A

Small programs that perform extra functionality and housekeeping tasks that keep computers running efficiently

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18
Q

What is encryption software?

A

Used to encode text so that it cannot be understood without knowing the key to decode it

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19
Q

How do you know if a connection to a website is encrypted?

A

Web browsers usually show a padlock for sites that are using HTTPS (Hypertext Transfer Protocol Secure)

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20
Q

Describe 4 uses of encryption software utilities.

A
  • Encrypt entire hard disks so that the data cannot be understood if the computer is stolen
  • Encrypt files and folders on a portable disk such as USB removable storage
  • Encrypt communication with websites
  • Encrypt data in an organisation’s database, especially sensitive data such as passwords
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21
Q

What is disk defragmentation?

A
  • When you save a large file it may not fit on the disk in consecutive memory locations
  • The file is referred to as ‘fragmented’
  • Defragmenting the hard disk reorganises files so they are stored together
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22
Q

Types of memory and storage that are used in computer systems

A
  • CPU registers
  • Cache
  • RAM
  • ROM
  • Secondary storage
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23
Q

Function of the clock

A

Controls the timing of the processor. It switches between 0 and 1 several million times per second and synchronises all CPU operations

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24
Q

What is a high level programming language?

A

A language that is closer to natural language, such as speaking English

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25
Q

What is a low level programming language?

A

A programming language that is close to the language that machines understand

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26
Q

What is RAM often referred to as?

A

Main memory, primary memory, primary storage

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27
Q

Why is RAM called Random Access Memory?

A

The name comes from the ability of the CPU to access any part of the memory in the same amount of time

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28
Q

What does RAM normally store at any one time?

A
  • The operating system (or part currently in use)
  • The software currently in use
  • The data which the software is using
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29
Q

Properties of RAM

A
  • It can be read from and written to
  • Access to RAM is much faster than a hard drive
  • RAM is volatile, loses data if the power is off
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30
Q

What is the difference between storage and memory?

A
  • Storage permanently keeps the data that is currently being used, so if the computer were to turn off data in storage is not lost.
  • Memory stores data currently being used temporarily as it is volatile, so if the computer turned off, data stored in memory would be lost forever.
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31
Q

Function of a compiler

A

Translates a high-level language into machine code

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32
Q

Function of an interpreter

A

Another type of program that translates a high-level language into machine code

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33
Q

Function of an assembler

A

Translates assembly code to machine code

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34
Q

What is the purpose of the CPU?

A

To fetch and execute instructions stored in memory

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35
Q

Describe Von Neumann architecture.

A
  • Program instructions and the data the programs are using are both stored in the same memory
  • The CPU accesses both instructions and data from the same RAM
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36
Q

What are the two major components of the CPU, and what is the purpose of each?

A

Arithmetic-Logic Unit (ALU) - carries out arithmetic and logic instructions
Control Unit - coordinates the CPU activities

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37
Q

Function of registers

A

A special fast memory location in the CPU. Stores small amounts of data, results of calculations, and instructions that the CPU is operating on

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38
Q

Function of the Control Unit

A

Coordinates and controls all the activities taking place within the CPU
- It decodes instructions and executes them
- It receives signals from the system clock
- It directs the timing and control of other parts of the CPU

39
Q

Describe the three buses that make up the system bus.

A

ADDRESS BUS - stores the address of the memory or device controller to be read from or written to
DATA BUS - carries data throughout the computer system
CONTROL BUS - uses control signals to control all activities within the CPU

40
Q

Purpose of the cache

A

Stores recently used data and instructions in memory that is faster to access than RAM

41
Q

What affects CPU performance and how does it affect it?

A

CLOCK SPEED - the faster the clock speed, the faster the instructions are processed
CACHE SIZE - the bigger the cache, the less time a processor has to wait for instructions to be fetched
NO. OF CORES - the more cores a CPU has, the greater the number of instructions it can process in a given space of time

42
Q

What is secondary storage?

A

Storage that is not directly accessible to the CPU. It is non-volatile.

43
Q

What is data rate?

A

The rate at which data can be accessed.

44
Q

Examples of non-volatile storage

A

USB stick, SD card, Blu-ray, CD/DVD, Hard Disk Drive (HDD), Solid State Drive (SSD)

45
Q

Uses of secondary storage

A
  • Programs and data are stored on hard drive
  • Blu-rays may be used to distribute films
  • Memory sticks may be used to transport data from one place to another
  • Magnetic tape or external hard drives may be used for backup
  • SD cards can be used for additional storage on camera and smartphones, this is used for music, video and photos
46
Q

Storage methods - solid state

A

Data is recorded onto solid memory chips without any moving parts

47
Q

Storage methods - optical

A

Lasers read and write data using light

48
Q

Storage methods - magnetic

A

Mechanical parts move over the disks surface to read and write data magnetically, or a drive head reads a magnetic tape

49
Q

Advantages of magnetic storage

A
  • They are a very cheap form of storage compared to solid state drives
  • They have a very large storage capacity, up to 6TB or more
  • Relatively fast write speed
50
Q

Disadvantages of magnetic storage

A
  • Lots of mechanical parts
  • Issues with durability, fragile
  • Sealed unit due to disk head and platter precision
  • Not very portable
51
Q

Uses of magnetic storage

A
  • Personal computers
  • Storage of large quantities of data
52
Q

Capacity of magnetic storage

A

500GB - 12TB or greater

53
Q

Advantages of optical storage

A
  • Cheap
  • Very easily portable
  • Takes up little space physically
54
Q

Disadvantages of optical storage

A
  • Less storage capacity compared to other types
  • Easily damaged/scratched
  • Requires a CD reader
  • Slow write speeds
55
Q

Uses of optical storage

A
  • Songs
  • Videos and other multi-media storage
  • Backup and archiving of data
56
Q

Capacity of optical storage

A

CD-ROM - up to 720 MB
DVD - up to 8.4 GB (dual layered disk)
Blu-Ray - up to 50 GB (dual layered disk)

57
Q

Basic features of optical storage

A
  • Data is stored as pits and lands burnt or pressed into a spiral track circulating outwards from the centre.
  • A laser beam passes over the pits and lands, the level of reflection is measured
  • From this signal, 0s and 1s can be derived
58
Q

Basic features of magnetic disks

A
  • Disk contains concentric circles called tracks
  • Each track is divided into sectors
  • Disk heads mounted on mechanical arms read and write the data

A disk with a solid platter is a ‘hard’ disk. Soft plastic disks are known as ‘floppy’ disks.

59
Q

Why are the capacities of these discs different given they are all the same physical size?

A
  • A CD has bigger pits and lands as red light has a larger wavelength
  • The smaller Blu-ray pits and lands allow it to store more data
60
Q

Basic features of Solid State Drives (SSD)

A
  • Solid-state drives use non-volatile flash memory to store information
  • Large electric current used to force electrons through a barrier and trap them on the other side
  • They remain on the other side until ‘flashed’ with a new current, hence the name
  • Trapped (charged) electron = 0 not trapped = 1
61
Q

Advantages of SSDs

A
  • Highly durable
  • No moving parts
  • Very fast read/write speed
  • No noisy fan or drive arm
  • Faster start up times
62
Q

Disadvantages of SSDs

A
  • More expensive than magnetic disks
  • Similar storage capacity as magnetic disks
63
Q

Uses of SSDs

A
  • Higher end computers
  • Laptops
  • Smartphones and tablets
64
Q

What is the capacity of a storage device?

A

How much data can be stored.

65
Q

What is the speed of a storage device?

A

The rate (usually in MB/s) at which data can be read or written

66
Q

What is the portability of storage devices?

A

How easy it is to carry/transport

67
Q

What is the durability of storage devices?

A

How easily damaged it is

68
Q

What is the reliability of storage devices?

A

How likely it is to lose the data

69
Q

What is the cost of storage devices?

A

Price per unit of storage

70
Q

Cloud storage

A
  • Refers to saving data in an off-site storage system maintained by a third party e.g. Dropbox, Google Drive or Amazon Web Services
  • Data is saved to servers at a remote location
  • These servers can use magnetic and/or solid-state storage
  • The data is accessed via the Internet
71
Q

Advantages of cloud storage

A
  • Easy to use, most companies offer apps for desktop and mobile devices to manage their data
  • Companies offer a high data storage capacity
  • Convenient to use, users can access data from anywhere with an Internet connection
  • Backups are carried out by the cloud provider so save the need for local backups
  • The data storage capacity can be increased easily as users need more
72
Q

Disadvantages of cloud storage

A
  • The data cannot be accessed without an Internet connection
  • A company needs to trust that the security of the cloud service is enough to stop a data breach, they won’t be directly able to control the security of the data
  • Uploading and downloading data could take a long time and is dependant on the available bandwidth of the user’s connection
73
Q

Parts of a hard disk

A
  • Magnetic platter contains data
  • Drive read/write head reads data on the drive
  • Actuator moves the read/write arm
  • Drive spindle rotates
74
Q

Logic circuit

A

A method of showing Boolean logic in a diagram using a set of symbols called logic gates

75
Q

what is application software?

A

Any program that is designed to enable the end user to perform a task

76
Q

System software

A

Provides a platform to run programs which maintain the computer system

77
Q

Primary storage

A

The memory in which the computer can store data or instructions that are currently in use. The two main types of primary storage is:
- Random Access Memory (RAM)
- Read Only Memory (ROM)

78
Q

Embedded system

A

A computer system which is built into another device to support its operation

79
Q

What does it mean for a language to be portable?

A

It can run on different types hardware

80
Q

Advantages of using low-level languages

A
  • Need less translation, and often lead to faster code which is useful for computers with low specifications such as embedded systems
  • Provide exact control over the CPU
81
Q

Compiler vs Interpreter

A

Compiler
- Translates a high-level language program in one go to produce source code
- A compiled program executes faster as it is already in machine code
- Produces an executable file so the original code does not need to be compiled again
- No need for the compiler to be present when the object code is run

Translater
- Translates and executes one line of a high-level language program at a time
- Takes more time to execute as each instruction is translated before it is excepted
- Original code will be interpreted or translated every time it is run
- The interpreter must be installed to run the program

82
Q

Fetch-Decode-Execute Cycle

A

The CPU operates by repeating three operations:
- FETCH, causes the next instruction to be fetched from main memory
- DECODE, decodes the instruction to work out what the instruction is
- EXECUTE, the instruction is executed
This process is then repeated

83
Q

Embedded systems usually avoid using hard disks in favour of flash memory. Why is that?

A

Moving parts a less reliable then solid state components which are also more robust

84
Q

System bus

A

The collection of wires or buses connecting the system components

85
Q

Advantages of an interpreter

A
  • Interpreters will stop as soon as they encounter an error, this is useful for debugging
  • Interpreted languages are ‘portable’, this means that they can be used on many different types of CPU as long as there is an interpreter available for the platform
86
Q

Disadvantages of an interpreter

A
  • Running an interpreted program is slower than running a compiled program because each line needs to be translated every time the software is run
  • Interpreters do not produce a compiled program file, the process must be repeated each time the program is run
87
Q

Data compression software

A
  • Utilities such as WinZip enable users to compress and decompress files or folders
  • This reduces the amount of storage space needed on a disk
  • If sending files, it reduces the amount of data that is sent
  • Compression may allow attachments to be sent via email that would otherwise have been larger than a file-size limit
  • More data can be stored on backup media
88
Q

What type of storage device are you most likely to find in a mobile phone?

A

Solid state, as there are no moving parts it’s a lot more durable and less prone to damage e.g. phone being dropped

89
Q

Why does a computer need secondary storage?

A
  • Secondary storage is a permanent store of programs and data
  • They cannot be held permanent in the RAM because it is volatile and relatively small
  • They can be held in ROM for embedded devices, but ROM cannot be updated as it is read only
90
Q

Why does increasing the clock speed of a CPU increase performance?

A

More instructions can be fetched, decoded and executed in the same amount of time

91
Q

Give three reasons why some programmers still use low-level languages

A
  • They may need to have greater control over the program in order to make a program with lower memory use
  • They may need to have greater control over what the CPU does in order to make the program run quicker
  • They may be trying to maintain old code or hardware
92
Q

Explain why programmers might prefer to use an assembly language over machine code

A

Assembly languages are more readable for humans than machine code so can be programmed and edited more easily

93
Q

State two reasons why computers have more RAM than cache memory

A
  • RAM stores the operating system and software currently in use so more is needed for a larger storage capacity
  • Cache is more expensive than RAM
94
Q

Explain why solid-state storage is not fitted to every new computer

A
  • Solid-state storage is expensive
  • Has relative lower storage capacity than magnetic storage

Computer Science (9 decks)

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