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GCSE Revision Flashcards > GCSE Computer Science - OCR J277 > Flashcards

GCSE Computer Science - OCR J277 Flashcards

FLASHCARDS MADE MYSELF WITH AID OF SOURCE BOOK: COMPUTER SCIENCE GCSE (9-1) FOR OCR J277 STUDENT BOOK BY DAVID WALLER

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1
Q

What does CPU stand for?

A

Central Processing Unit

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2
Q

What is the purpose of the CPU?

A

The CPU is responsible for executing the instructions given to it in a program. It is the component of the computer that controls the other devices, executes the instructions and processes the data.

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3
Q

What was the name of the first computer?

A

ENIAC

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4
Q

Where does data processing take place?

A

CPU

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5
Q

What is Von Neumann architecture?

A

The way the CPU is designed and executes the program instructions. It is a ‘stored program’ computer where both the program and the data are stored in the memory.

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6
Q

What year did John von Neumann propose his ‘stored program’ computer design?

A

1945

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7
Q

What problem did Von Neumann architecture solve in 1945?

A

Prior to 1945, computers had to be rebuilt for each new program that was needed.

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8
Q

What does ‘execute’ mean in a computer science context?

A

To run a computer program or process.

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9
Q

What is the bus in Von Neumann architecture?

A

A bundle of wires carrying data from one component to another or a number of tracks on a printed circuit board (PCB) fulfilling the same function.

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10
Q

What does PCB stand for?

A

Printed Circuit Board

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11
Q

What does RAM stand for?

A

Random Access Memory

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12
Q

What is RAM?

A

Memory that can be used by computer programs to store data and instructions, but all of its data is lost when the computer is switched off.

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13
Q

What is a collection of wires that carry signals or communications between the various components of a computer system called?

A

A bus

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14
Q

What does the control bus connect?

A

The control unit (CU) with the other components of the CPU and devices in the computer system.

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15
Q

What does the control unit use the control bus for?

A

To send instructions to other components of the computer.

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16
Q

What is the data bus used for?

A

The transfer of data between the CPU and the RAM and the address bus for the CPU to access memory locations in the main memory.

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17
Q

What happens before the fetch-decode-execute cycle starts?

A

The program instructions are copied from a storage device such as a hard disk drive or DVD to the primary storage or RAM.

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18
Q

What is the fetch-decode-execute cycle?

A

The way in which the Von Neumann architecture executes the program instructions.

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19
Q

What happens during the fetch part of the fetch-decode-execute cycle?

A

Instructions and data are moved from the RAM to the CPU.

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20
Q

What happens during the decode part of the fetch-decode-execute cycle?

A

The control unit (CU) decodes or interprets the instructions and decides what action to perform.

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21
Q

What happens during the execute part of the fetch-decode-execute cycle?

A

The decoded instructions are now carried out by the control unit (CU). If a calculation needs to performed then it instructs to ALU (Arithmetic Logic Unit).

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22
Q

What does ALU stand for?

A

Arithmetic Logic Unit

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23
Q

What is the function of the ALU?

A

To perform arithmetic and logical operations. It carries out activities such as:
1. addition and subtraction
2. multiplication and division
3. logical tests using logic gates (Boolean logic)
4. comparisons, such as whether one number is greater than another

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24
Q

What does CU stand for?

A

Control Unit

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25
Q

What are control signals?

A

Electrical signals that are sent out to all of the devices to check their status and give them instructions.

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26
Q

What is a register?

A

A storage location that is inside the CPU itself and stores the instructions and data that are currently being used in the fetch-decode-execute cycle.

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27
Q

What is the purpose of the CU?

A

The CU coordinates the actions of the computer and controls the fetch-decode-execute cycle by sending out control signals to the other parts of the CPU such as the ALU and registers. It also sends signals to other components of the computer system such as the input and output devices. The 2 main elements of the CU are the clock and the decoder.

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28
Q

What are the 2 main elements of the CU?

A

The clock and the decoder.

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29
Q

What is clock speed measured in?

A

Cycles per second

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30
Q

What is the rate of one Hertz?

A

One cycle per second

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31
Q

What is the rate of one megahertz (MHz)?

A

One million cycles per second

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32
Q

What is the rate of one gigahertz (GHz)?

A

One billion cycles per second

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33
Q

What are the common rates (in GHz) in most home computers?

A

Rates of between one and three GHZ

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34
Q

Why does the clock in the CU send out pulses?

A

Pulses are sent out to the other components to coordinate their activities and ensure instructions are carried out and completed.

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35
Q

What controls the timing of the pulses sent out by the CU’s clock?

A

A vibrating quartz crystal

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36
Q

How many instructions can be carried out with each pulse of the clock?

A

One

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37
Q

How does the clock speed impact the CPU speed?

A

The higher the clock speed, the faster the CPU will be able to carry out the program instructions.

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38
Q

What is the function of the decoder in the CU?

A

The decoder is the part of the CU that decodes the program instructions to work out what they mean and decide what actions should be taken. It then sends control signals to the other components to carry them out.

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39
Q

True or false: Registers can be accessed faster then RAM.

A

True

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40
Q

What is the function of registers?

A

Registers are storage locations within the CPU. The function of these registers is to store instructions and data that are currently being used in the fetch-decode-execute cycle.

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41
Q

What are general purpose registers used for?

A

The quick storage of data items.

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42
Q

Name the 4 main registers which are not general purpose registers as they serve specific functions:

A
  1. the accumulator (A or ACC)
  2. the program counter (PC)
  3. the memory address register (MAR)
  4. the memory data register (MDR) or memory buffer register (MBR)
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43
Q

What are storage locations in Von Neumann architecture?

A

Places in RAM where a single piece of data can be kept until they are needed.

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44
Q

What does the CPU consist of?

A
  1. control unit (CU)
  2. arithmetic and logic unit (ALU)
  3. registers
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45
Q

How does the CPU control the activities of the CPU?

A

By sending out control signals.

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46
Q

What is the function of the ALU?

A

To carry out arithmetic and logic operations.

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47
Q

What are registers?

A

Registers are the memory stores within the CPU, which can be accessed faster than RAM.

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48
Q

What is overclocking?

A

The process of increasing the clock speed to a higher level than that recommended by the manufacturer.

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49
Q

What are the risks of overclocking?

A

Overclocking causes an increase in heat and can result in instability and permanent damage to the processor.

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50
Q

What is a heat sink?

A

A metal device, glued to the CPU chip with thermally conducting paste, to transfer the heat away from the chip.

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51
Q

What does clock speed control?

A

The rate at which instructions are processed.

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52
Q

How does clock speed impact the rate of processing?

A

The faster the clock speed, the faster the rate of processing.

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53
Q

What is the problem with microprocessors with clock speeds of 9 GHz?

A

They require cooling by liquid nitrogen.

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54
Q

What are the limitations of increasing clock speed to increase processing speed?

A
  1. Microprocessors with clock speeds of 9 GHz require cooling by liquid nitrogen.
  2. The microprocessor generates a large amount of heat and this heat increases with clock speed. Although heat is dissipated by a fan and heat sink to prevent it from malfunctioning (and eventually melting) there are limits to the rate of cooling.
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55
Q

When do bottlenecks occur?

A

Bottlenecks occur when one component cannot work as fast as other components and so hinders progress.

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56
Q

True or false: It is far quicker to fetch instructions from RAM than from a hard disk drive.

A

True. However, (while it is quicker to fetch the instructions) the RAM is still far slower than the CPU and then the instructions still need to be transferred through the data bus. This is why cache needed to be created as a solution.

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57
Q

Why is the speed of processing limited by RAM?

A

RAM supplies the instructions regardless of how much clock speed is increased or how many cores are used. This is why cache needed to be created as a solution.

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58
Q

What is cache?

A

Memory used to store recently used data and data likely to be frequently used so that they can be accessed more quickly.

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59
Q

What is the difference between data and instruction caches?

A

Data caches have to be read and written to but instruction caches just have to be read by the CPU.

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60
Q

Where are caches located?

A

On the processor chip.

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61
Q

Which level of cache is the fastest?

A

There are 3 levels of cache. Level 1 is both the fastest and the smallest.

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62
Q

Which level of cache is the smallest?

A

Level 1

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63
Q

Which level of cache is the slowest?

A

There are 3 levels of cache. Level 3 is the slowest.

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64
Q

Which year did manufacturers introduce multi-core processors?

A

2006

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65
Q

Why does a multi-core processor have a faster processing speed?

A

A multi-core processor has more than one CPU.

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66
Q

What is a processor with one core called?

A

Single-core processor

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67
Q

What is a processor with two cores called?

A

Dual-core processor

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68
Q

What is a processor with four cores called?

A

Quad-core processor

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69
Q

What is a processor with 5 cores called?

A

Penta-core processor

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70
Q

What is a processor with 8 cores called?

A

Octa-core processor

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71
Q

What is a processor with 10 cores called?

A

Deca-core processor

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72
Q

What is parallel processing? HINT: OPPOSITE OF MULTI-TASKING

A

When the processor cores work on different parts of the same program.

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73
Q

What is multitasking? HINT: OPPOSITE OF PARALLEL PROCESSING

A

When the processor cores work on different programs at the same time.

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74
Q

What are the advantages of multi-core processors over single core processors?

A
  1. the cores can work together on the same program; this is called parallel programming
  2. the cores can work on different programs at the same time; this is called multi-tasking
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75
Q

Why can clock speed not be increased indefinitely?

A

Because of the extra heat that is generated.

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76
Q

What is a multi-core processor?

A

A processor with multiple CPUs.

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77
Q

What limits the processing speed of the CPU?

A

The CPU’s processing speed is limited by the speed that data can be supplied by the slower RAM.

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78
Q

What does cache memory store?

A

Regularly used items of data so that they can be accessed more quickly.

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79
Q

What happens when RAM is full? (Where will the operating system store data?)

A

When RAM is full, the operating system will store data on an area of the hard disk drive known as virtual memory.

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80
Q

What is an embedded system?

A

A computer system built within a larger device to carry out specific tasks. They are generally limited to a certain number of tasks, unlike general purpose computer systems such as laptops and desktops.

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81
Q

Give an example of an embedded system:

A
  1. washing machines
  2. dishwashers
  3. microwaves
  4. digital cameras
    etc.
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82
Q

True or false: all the components in an embedded system, including the microprocessor, memory and input and output devices are on a single printed circuit board. The memory contains the program and the board is merely a component built into a larger device hence the name ‘embedded’.

A

True.

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83
Q

Why are the programs in an embedded system often written in an assembly language, rather than a higher level programming language?

A

So that the hardware components can be more easily controlled.

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84
Q

What is an embedded system?

A

A computer system built into a larger device that carries out a limited number of functions. All of the components (memory, microprocessor, input/output devices) are stored on a single PCB, with the memory containing the program.

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85
Q

What is a PCB?

A

A PCB (Printed Circuit Board) is the base that supports the wiring and electronic components that are soldered to it or fit into sockets on the board.

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86
Q

What is hardware?

A

The physical components making up the computer, and its peripheral devices.

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87
Q

What is primary storage?

A

Storage that can be accessed directly by the CPU, usually referred to as ‘memory’.

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88
Q

What is secondary storage?

A

Permanent storage for data that does not need to be frequently accessed.

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89
Q

Why is RAM used by the CPU?

A

It takes a long time to fetch data and program instructions from the hard drive. Therefore, they are stored in RAM, a temporary store of data, so that the information can be retrieved quickly by the CPU when required for the program it is running.

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90
Q

Why does each byte of date have an address?

A

So that the CPU knows where to store and retrieve the instructions and data.

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91
Q

Why is RAM said to be ‘Random Access’?

A

Because each memory location can be accessed in any order if the ‘address’ of that location is specified. This speeds up data retrieval as the CPU can go to any location and does not have to start each time at the first location and go through them in order until it finds the correct one. This is called serial access.

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92
Q

What is serial access? HINT: RANDOM ACCESS MEMORY

A

When the CPU has to search each memory location by starting at the first location and and going through them in order until it finds the correct one.

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93
Q

What does it mean to say RAM is volatile?

A

RAM is said to volatile because if there is no electrical power then the RAM will lose all of its data.

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94
Q

What are the different types of RAM?

A

DRAM and SRAM

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95
Q

What does DRAM stand for?

A

Dynamic RAM

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96
Q

What does SRAM stand for?

A

Static RAM

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97
Q

Why is DRAM used as the main memory store, despite being slower than SRAM?

A

Because it is cheaper.

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98
Q

True or false: DRAM is slower than SRAM.

A

True. Despite DRAM being slower than SRAM it is still used as the main memory store because it is cheaper.

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99
Q

How large is a byte?

A

8 bits

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100
Q

What is an address?

A

A number assigned to the storage location so that it can be accessed.

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101
Q

What does volatile mean?

A

Data is permanently lost when the power is switched off.

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102
Q

What does BIOS stand for?

A

Basic Input/Output System

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103
Q

What is the function of the BIOS?

A

The BIOS system controls the computer when it is first switched on. It tests the system hardware and loads the operating system. It is specially written for each motherboard and performs any other operations that are needed by that particular motherboard.

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104
Q

What does ROM stand for?

A

Read-Only Memory

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105
Q

What is ROM? HINT: THINK IN TERMS OF HARDWARE

A

ROM is an integrated circuit on a chip. It is programmed with specific data to perform a particular function then it is manufactured.

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106
Q

List the functions of the BIOS:

A
  1. the BIOS controls what happens when the computer is first switched on
  2. the BIOS checks the hardware devices to ensure there are no errors
  3. the BIOS loads basic software so that it can communicate with these hardware devices. It then locates and passes control to the operating system.
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107
Q

What does it really mean to say that ROM is ‘Read-Only’?

A

The data can be read but it cannot be changed; the computer cannot write to the chip, unlike RAM.

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108
Q

ROM is non-volatile. What does non-volatile mean?

A

ROM is non-volatile as the data is not lost when the power is turned off.

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109
Q

What does RAM act as?

A

A temporary store of program instructions and data.

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110
Q

What is RAM made up of?

A

RAM consists of billions of memory locations with unique addresses which can be accessed in any order.

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111
Q

What is ROM used to store?

A

Basic information and instructions that a computer needs when it is starting up (booting).

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112
Q

What are applications?

A

Programs that are called up by the systems software and which perform specific tasks.

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113
Q

When could RAM become full?

A

When the computer is running the operating system and several applications.

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114
Q

Explain the 4 steps of the computer calling in virtual memory and swapping in and out data stored in RAM.

A
  1. a process running on the computer may need to store data in the physical memory.
  2. if there is no free memory, the memory manager will ‘swap out’ some of the data stored in RAM to the swap area on the hard disk drive and ‘swap in’ the requested data into the now free area.
  3. usually the least recently used stored data is swapped out.
  4. if data is swapped out and then is needed again, it is swapped back in, from the swap area, at the expense of the data.
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115
Q

True or false: the size of the area on the hard disk drive to be used for virtual memory can be set by the user.

A

True

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116
Q

What are the three main disadvantages of virtual memory?

A
  1. the read/write speed of a hard drive is much slower than RAM, as the technology of a hard drive is not geared towards accessing multiple small pieces of data at a time.
  2. if the system has to rely too heavily on virtual memory, there will be a significant performance drop.
  3. often the operating system has to constantly swap information back and forth between RAM and the hard disk drive, which operates all of the time. You can hear the disk drive operating continuously. This is called ‘disk thrashing’ and significantly slows down the execution of programs.
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117
Q

What is virtual memory?

A

Virtual memory is the use of secondary storage as additional primary memory.

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118
Q

What is disk thrashing?

A

Often the operating system has to constantly swap information back and forth between RAM and the hard disk drive, which operates all of the time. You can hear the hard disk drive operating continuously. This is called ‘disk thrashing’ and significantly slows down the execution of the programs.

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119
Q

Why will inserting more RAM significantly improve the performance of a computer?

A

The more RAM a computer has then the less virtual memory will be needed. Virtual memory has a much slower read/write speed as the technology of a hard drive is not geared towards accessing multiple small pieces of data at a time.

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120
Q

What is execution?

A

When a program or part of a program is run by the computer.

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121
Q

What are secondary storage devices?

A

Devices that store information but which do not lose the data when they are switched off; usually not on the main circuit (motherboard).

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122
Q

What is optical storage?

A

Storing data using optical devices such as CDs and DVDs.

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123
Q

What is solid state storage?

A

Storing data using devices such as flash memory. This is sometimes called ‘electrical’ storage.

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124
Q

What are the three types of secondary storage?

A
  1. magnetic storage
  2. optical storage
  3. solid state storage
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125
Q

What are the three types of secondary storage?

A
  1. magnetic storage
  2. optical storage
  3. solid state storage
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126
Q

Why do we use secondary storage devices?

A

Because RAM is volatile, data must be stored on devices called secondary storage devices so that the data is not lost when the power is turned off.

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127
Q

How does optical storage work?

A

Optical storage uses light from lasers to read and write data on discs. To write data to a disk, a laser beam encodes data onto a disk via burning pits onto the disk’s surface in a spiral track.

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128
Q

How much data can a CD typically store?

A

CDs typically store 700MB.

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129
Q

How much data can a DVD typically store?

A

DVDs typically store 4.7 GB.

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130
Q

What does CD stand for?

A

Compact Disk

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131
Q

What does DVD stand for?

A

Digital Versatile Disk

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132
Q

How much data can a Blu-ray disk typically store?

A

128 GB

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133
Q

Give two advantages of optical storage:

A
  1. cheap
  2. easy to transport from one site to another
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134
Q

Give five disadvantages of optical storage devices:

A
  1. less storage space than hard disk drives
  2. slow access speeds
  3. stored data degrades over time
  4. risk of disk scratching
  5. data cannot be written over unlike with hard disk drives
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135
Q

Give three examples of magnetic storage devices:

A
  1. hard disk drives
  2. magnetic tape
  3. floppy disk drives
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136
Q

What do hard disk drives consist of and how do they work? HINT: THINK HARDWARE

A

Hard disk drives consist of stacks of non-removable disks coated with magnetic materials. The disks spin and read-write heads move across them. Electro-magnets in the read-write heads read and write the data.

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137
Q

What is magnetic storage?

A

Storing data using magnetic media such as a hard disk drive.

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138
Q

When is magnetic storage most suitable?

A

Hard disk drives are suitable for the storage and backup of large amounts of data that do not need to be transported.

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139
Q

When is optical storage most suitable?

A

Optical disks are most suitable for distributing program files and images, and backing up data which can then be stored at another site.

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140
Q

Give two disadvantages of magnetic storage:

A
  1. not very portable
  2. susceptible to physical knocks that may cause the read-write heads to hit the disks and corrupt data
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141
Q

Give four advantages of magnetic storage:

A
  1. very fast access speeds
  2. random access: data can be read instantly from any part of the disc
  3. low cost
  4. can store large amounts of data; hard disk drives that store terabytes of data are common in most home computers
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142
Q

What does SSD stand for?

A

Solid State Drive

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143
Q

What does SD card stand for?

A

Secure Digital card

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144
Q

Give five examples of solid state storage:

A
  1. SSDs
  2. SD cards
  3. Micro SD cards
  4. SDXC (extended capacity) cards
  5. USB drives
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145
Q

How much data can an SD card typically store?

A

4 - 32 GB

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146
Q

How much data can a Micro SD card typically store?

A

4 - 32 GB

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147
Q

How much data can an SDXC (extended capacity SD card) store?

A

2 TB

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148
Q

How much data can a USB drive typically store?

A

256 GB - 1 TB

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149
Q

When is solid state memory most commonly used?

A

Data storage in cameras, mobile phones and embedded devices. It is also increasingly used as the main secondary storage device in computers, especially in laptops as SSDs.

150
Q

What is the main secondary storage device used by the MacBook Air?

A

SSD

151
Q

When are solid state drives most suitable?

A

Solid state memory devices are ideal for transporting data as they are light and have no moving parts which could be damaged.

152
Q

Give four advantages of solid state storage:

A
  1. very fast access speed; much faster than optical discs
  2. portable - small and light
  3. quiet
  4. has no moving parts that could be damaged if the device was knocked or dropped and therefore there is less chance of losing data
153
Q

Give three disadvantages of solid state storage:

A
  1. more expensive than a HDD or optical disc
  2. less storage capacity than a HDD
  3. limited number of erase/write cycles, up to 100000 for high quality SSDs and so it cannot be used indefinitely
154
Q

Analyse magnetic storage devices in terms of capacity, speed, portability, durability, reliability and cost:

A
  1. capacity - very large
  2. speed - fast
  3. portability - not very portable as physical knocks may cause the read-write heads to hit the discs and corrupt the data
  4. durability - very durable
  5. reliability - very reliable
  6. cost - very low
155
Q

Analyse optical storage devices in terms of capacity, speed, portability, durability, reliability and cost:

A
  1. capacity - low
  2. speed - slow
  3. portability - more portable than HDD but discs are still relatively slow
  4. durability - easily scratched and data can be damaged. Data cannot be overwritten
  5. reliability - very reliable if not scratched
  6. cost - very low
156
Q

Analyse solid state storage devices in terms of capacity, speed, portability, durability, reliability and cost:

A
  1. capacity - large (usually around 1TB)
  2. speed - very fast
  3. portability - very portable
  4. durability - lower than a HDD, limited number of erase/write cycles
  5. reliability - very reliable, data is not affected by magnetic fields as it is in HDD
  6. cost - most expensive but becoming cheaper
157
Q

What is cloud storage?

A

Off-site storage accessed over the internet.

158
Q

What are bits (also known as binary digits)?

A

0 and 1

159
Q

Explain how the CPU carries out the program instructions.

A

The CPU carries out all of the program instructions by carrying out millions of calculations each second. These calculations are performed by billions of transistors acting as switches. The transistors are either on or off - they have two states, they either transmit an electric current or they do not.

160
Q

What are computer programs made up of?

A

Lists of instructions switching transistors off or on (to be represented by 0 and 1).

161
Q

What do binary digits represent?

A

They are 0 and 1 and represent the codes for instructions and data.

162
Q

How many bits in a nibble?

A

4

163
Q

How many bits in a byte?

A

8

164
Q

How many bytes in a KB?

A

1000 bytes

165
Q

How many KB in a MB?

A

1000 KB

166
Q

How many MB in a GB?

A

1000 MB

167
Q

How many GB in a TB?

A

1000 GB

168
Q

How many TB in a PB?

A

1000TB

169
Q

What is the acronym for remembering the increasing order of file size? BITS –> PETABYTES

A

Bold - BIT
Blue - BYTE
Kites - KILOBYTE
Make - MEGABYTE
Great - GIGABYTE
Toy - TERABYTE
Planes - PETABYTE

170
Q

What does KB stand for?

A

Kilobyte

171
Q

What is the magnitude of a KB? HINT: IN TERMS OF 10 TO THE POWER OF N

A

10^3 bytes

172
Q

What does MB stand for?

A

Megabyte

173
Q

What is the magnitude of a MB? HINT: IN TERMS OF 10 TO THE POWER OF N

A

10^6 bytes

174
Q

What does GB stand for?

A

Gigabyte

175
Q

What is the magnitude of a GB? HINT: IN TERMS OF 10 TO THE POWER OF N

A

10^9 bytes

176
Q

What does TB stand for?

A

Terabyte

177
Q

What is the magnitude of a TB? HINT: IN TERMS OF 10 TO THE POWER OF N

A

10^12 bytes

178
Q

What does PB stand for?

A

Petabyte

179
Q

What is the magnitude of a PB? HINT: IN TERMS OF 10 TO THE POWER OF N

A

10^15 bytes

180
Q

True or false: Transistors act as switches which either conduct electricity (represented by the binary digit 1) or they do not (represented by the binary digit 0). The system consists of these two states, so is called a binary system.

A

True

181
Q

What does it mean to say a number system is base 10?

A

Each place value is 10 times bigger than the place to its right.

182
Q

Which number system do we use?

A

Denary

183
Q

Which base does denary use?

A

Base 10

184
Q

What are place values?

A

A place value is the value that a digit’s position in a number gives it. For example (for decimal) in the number 356, the digit 5 has a value of 50 whereas in the number 3560, the digit 5 has a value of 500.

185
Q

What does it mean to say a number system is base 2?

A

Each place value is 2 times bigger than the place to its right.

186
Q

Which base does binary use?

A

Base 2

187
Q

Which number system does a binary system use?

A

Binary

188
Q

What is the denary equivalent of 2^0 bits in a byte?

A

1

189
Q

What is the denary equivalent of 2^1 bits in a byte?

A

2

190
Q

What is the denary equivalent of 2^2 bits in a byte?

A

4

191
Q

What is the denary equivalent of 2^3 bits in a byte?

A

8

192
Q

What is the denary equivalent of 2^4 bits in a byte?

A

16

193
Q

What is the denary equivalent of 2^5 bits in a byte?

A

32

194
Q

What is the denary equivalent of 2^6 bits in a byte?

A

64

195
Q

What is the denary equivalent of 2^7 bits in a byte?

A

128

196
Q

How many bits does one binary number have? FOR EXAMPLE: 10011010

A

8

197
Q

What does MSB stand for?

A

Most Significant Bit

198
Q

What is the MSB?

A

The bit with the largest value, farthest to the left.

199
Q

What does LSB stand for?

A

Least Significant Bit

200
Q

What is the LSB?

A

The bit with the lowest value, farthest to the right.

201
Q

What are bits?

A

BInary digiTs - they have single binary values of either 0 or 1.

201
Q

What is an integer?

A

A whole number without decimals (can be positive or negative).

202
Q

What are the three rules of binary addition?

A

0 + 1 = 1
0 + 0 = 0
1 + 1 = 0 CARRY THE 1
1 + 1 + 1 = 1 CARRY THE 1

203
Q

What is an overflow error?

A

When a calculation produces a result that is greater than the range of values that the computer can represent or store.

204
Q

What is the most famous example of an overflow error?

A

The crash of the Ariane 5 space rocket launched by the ESA (European Space Agency) in 1996.

205
Q

True or false: Binary numbers can only be added and subtracted.

A

False. Addition, subtraction, multiplication and division can be carried out on binary numbers in the same way as denary ones.

206
Q

What base does the hexadecimal system use?

A

Base 16

207
Q

What is A in hex?

A

10

208
Q

What is B in hex?

A

11

209
Q

What is C in hex?

A

12

210
Q

What is D in hex?

A

13

211
Q

What is E in hex?

A

14

212
Q

What is F in hex?

A

15

213
Q

How many digits are in the hexadecimal system?

A

16 digits - 0 to 15

214
Q

List the hexadecimal digits:

A

0 1 2 3 4 5 6 7 8 9 A B C D E F

215
Q

True or false: Computers understand hexadecimals.

A

False. Computers only understand and use the binary system.

216
Q

Why do we use hexadecimal numbers?

A

Human limitations - we get confused by large binary numbers so we simplify them by representing them in hex notation. Saves time.

217
Q

How many bits in a colour code?

A

24 bits

218
Q

How are colour codes represented?

A

Hexadecimal numbers - far easier to represent the codes as 6 hex numbers than 24 binary ones. EXAMPLE OF A COLOUR CODE: #CC3399.

219
Q

Why are # signs placed before hexadecimal numbers?

A

To let people know that the number is a hexadecimal number.

220
Q

Give 2 examples of when hexadecimals are used:

A
  1. Error messages
  2. Assembly language programming
  3. Colour codes
  4. Short-hand for binary numbers
220
Q

Give 4 examples of when hexadecimals are used:

A
  1. Error messages
  2. Assembly language programming
  3. Colour codes
  4. Short-hand for binary numbers
221
Q

ASCII - What is ‘A’?

A
  1. You can work out any uppercase letter from this by counting up to the letter (ie. Z is 90) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.
222
Q

ASCII - What is ‘a’?

A
  1. You can work out any lowercase letter from this by counting up to the letter (ie. z is 122) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.
223
Q

ASCII - What is ‘0’?

A
  1. You can work out any number 0-9 from this by counting up to the number (ie. 9 is 57) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.
224
Q

ASCII - What is ‘ ‘? HINT: SPACE

A
  1. Convert to binary if needed in that form.
225
Q

ASCII - What is DEL?

A

127 -> 01111111

226
Q

What is a character set?

A

The list of binary codes that can be recognised by the computer hardware and software as being usable characters.

227
Q

Why was ASCII created as the first common encoding system for text?

A

Different manufacturers used to use their own codes for their computers. However, they soon realised that if computers wanted to share information, they needed to also share a common encoding system for text.

228
Q

What does ASCII stand for?

A

American Standard Code for Information Interchange

229
Q

How many bits does ASCII use?

A

7 bits. It can represent 128 possible code sequences - these represent English characters and control actions (backspace, shift on, etc.).

230
Q

What is pseudocode?

A

A language that is similar to real programming language, but is easier for humans to understand although it doesn’t actually run on a computer. It can be easily converted to a regular programming language.

231
Q

Why was Extended ASCII created?

A

ASCII had 92 printable characters but there was always a need for more to accommodate foreign languages, mathematical symbols and special symbols for drawing pictures.

232
Q

How many bits does Extended ASCII use?

A

Extended ASCII uses the full 8 bits and was created to cater for foreign languafgees and graphics characters.

233
Q

How many codes are in the character set allowed by Extended ASCII?

A

256

234
Q

What can Unicode represent?

A

Unicode can represent characters in all known languages and writing systems.

235
Q

Why was Unicode introduced?

A

The Unicode Consortium introduced Unicode due to too many different versions of Extended ASCII developed by different manufacturers such as IBM and Apple.

236
Q

How many codes are in the character set allowed by ASCII?

A

128

237
Q

How many bits does Unicode use?

A

16 bits.

238
Q

How many codes are in the character set allowed by Unicode?

A

Unicode uses 16 bits, allowing the use of over 65,000 characters.

239
Q

What is a pixel?

A

A pixel is the smallest possible dot on a computer screen, represented by a number of bits.

240
Q

What are images made up of?

A

A digital image is composed of many small points of colour or picture elements, pixels for short.

241
Q

How is the size of an image given?

A

The number of pixels in the width and then the number of pixels in the height. For example, 640 x 480 or 2048 x 1536.

242
Q

How does resolution affect image quality?

A

Higher resolution, better image quality.

243
Q

What is resolution?

A

The number of pixels per square inch on the computer screen. The higher the resolution, the better the picture.

244
Q

What is colour depth?

A

The number of bits used to encode the colour of each pixel.

245
Q

How many colours can be used in an image/graphic if only one bit is used to encode each pixel?

A

Only two colours can be used (2^1). The 0 represents black and the 1 represents white.

246
Q

A colour depth of three would allow how many colours to be used?

A

2^3 is 8. So 8 colours could be used.

247
Q

What is the current standard for colour depth (in bits) when representing images?

A

24-bit representation. This means that the colour data for each pixel is encoded in 24 bits with 8 bits used for each of the primary colours: red, green and blue. Each colour in the palette is a combination of these in different proportions.

248
Q

How many colour variations are allowed by 8-bit encoding?

A

Using 8-bits allows 256 different levels of each red, green and blue. Therefore 256 x 256 x 256 = 16,777,216 different colour variations are possible. This number of bits produces such a realistic image it is described as being ‘true colour’.

248
Q

In computer science, what are the primary colours?

A

Red, green and blue

249
Q

I know the number of bits. How can I find the equivalent number of bytes?

A

Divide the number of bits by 8.

250
Q

I know the number of bytes. How can I find the equivalent number of kilobytes?

A

Divide the number by 1000.

251
Q

How does colour depth and number of pixels impact file size?

A

As the number of pixels and colour depth increase, then so will the size of the image file.

252
Q

What is the equation for calculating file size of an image?

A

W x H x CD (Width x Height x Colour Depth used)

253
Q

How does image quality impact file size?

A

Better image quality, greater file size.

254
Q

Why is image quality often reduced before transmitting an image electronically?

A

To reduce the amount of time it will take to download the image after transmitting - there is always a compromise between file size and image quality. Lower image quality = faster download speeds.

255
Q

What is metadata?

A

Data about data. Included in many files, in addition to the stored data, is information about the file.

256
Q

Give 2 examples of metadata:

A
  1. When the file was last saved
  2. Who created the file
  3. What the file is named
  4. When the file was created (date/time)
257
Q

What does Exif stand for?

A

EXchangeable Image File format. The metadata stored in a digital image file contains descriptive and technical information (such as point of capture) and the data is stored in the Exif format.

258
Q

What data could be stored in Exif for image files?

A
  1. Make and model number of the camera
  2. Aperture setting
  3. Speed settings
  4. Dimensions of the image and the resultant file size
259
Q

What is sound caused by?

A

Vibrations travelling through a medium such as air, water or metal. These vibrations compress and then pull apart the air molecules thus causing changes in air pressure.

260
Q

Vibrations travel out in waves - what are these called?

A

Sound waves

261
Q

What do the sound wave vibrations cause in terms of air pressure?

A

Continuous changes to air pressure. These are shown on analogue diagrams.

262
Q

What are analogue recordings?

A

Recording methods that try to capture the continuous changes in air pressure by trying to convert all of the changes to analogous changes in voltage.

263
Q

Give 2 examples of analogue recordings?

A
  1. vinyl albums
  2. audio cassettes
    These can capture the continuous changes in air pressure as minute changes in voltage.
264
Q

Why do computers not use analogue recordings?

A

Computers are digital. They cannot represent continuous, minute changes in voltage; each transistor is either on or off, nothing in between.

265
Q

What does analogue mean?

A

Data which can use any value in a continuous range.

266
Q

What is sampling?

A

Making a physical measurement of the amplitude of the wave at set time intervals and then converting the measurements to digital values.
Think of it as similar to making an animation - the smaller the changes between each sample and the greater number used each second, the more realistic the animation.

267
Q

What are the advantages of digital sound files? HINT: ANSWER NAMES 7

A
  1. it can be edited and manipulated easily by computer equipment
  2. it is more portable; it can be carried on a memory stick or SD card while a vinyl record or tape are not as portable
  3. it can be played over and over again without deterioration. LPs and tapes deteriorate.
  4. it can be easily copied on a computer. Expensive equipment is needed to copy a vinyl record.
  5. digital audio files can be easily emailed, downloaded and streamed by users.
  6. equipment to record and process digital sound is relatively cheap.
  7. it has allowed people to produce their own commercial music at home.
268
Q

What are the advantages of digital sound files? HINT: ANSWER NAMES 7

A
  1. it can be edited and manipulated easily by computer equipment
  2. it is more portable; it can be carried on a memory stick or SD card while a vinyl record or tape are not as portable
  3. it can be played over and over again without deterioration. LPs and tapes deteriorate.
  4. it can be easily copied on a computer. Expensive equipment is needed to copy a vinyl record.
  5. digital audio files can be easily emailed, downloaded and streamed by users.
  6. equipment to record and process digital sound is relatively cheap.
  7. it has allowed people to produce their own commercial music at home.
269
Q

What are the two factors that impact how accurately a digital recording will match the original sound?

A

Sample rate and bit depth

270
Q

What is sample rate?

A

The number of samples taken each second. The higher the sample rate, the more accurately the sound will be represented.

271
Q

For CDs, what is the average sample rate?

A

44,100 samples per second (44.1KHz)

272
Q

For Blu-ray audio, what is the average sample rate?

A

96,000 samples per second (96KHz)

273
Q

How many KHz is one sample when converting audio to digital form?

A

1000

274
Q

What is bit depth when converting audio to digital format?

A

The number of bits used to encode each sample.

275
Q

How does increasing bit depth impact digital audio quality?

A

Higher bit depth = more bits used to encode each sample = more accurate representing of range of sound = better audio quality

276
Q

What is the dynamic range?

A

The range of volume of sound in music.

277
Q

For CDs, what is the bit depth used for digital audio?

A

16 bits

278
Q

For CDs, what is the bit depth used for digital audio?

A

16 bits

279
Q

What is the equation for calculating digital audio file sizes?

A

sample rate x bit depth x length in seconds (x number of channels (mono or stereo) if applicable)

280
Q

What is compression?

A

Reducing the size of a file so that it takes up less storage space or bandwidth when it is transmitted.

281
Q

What are the benefits of compression? HINT: ANSWER NAMES 5

A
  1. it uses less internet bandwidth when files are downloaded
  2. transfer speed is quicker
  3. takes up less storage space on the servers of storage providers
  4. smaller files reduce congestion on the Internet, which is good for everyone
  5. it makes audio and video files suitable for streaming
282
Q

What is lossless compression?

A

Compression where a compressed file can be decompressed to the original without any loss of data - all information will remain intact.

283
Q

What is lossy compression?

A

Compression where data is lost in the compression process and when the file is decompressed it will not contain all of the original information.

284
Q

What is a server?

A

A computer that provides files on demand to client machines.

285
Q

What is redundancy?

A

The number of items of data in a file which are repeated.

286
Q

Why are lossless compression rates of 50% relatively easy to achieve with text files?

A

They have lots of repeated items (words) and characters which are redundant and can be compressed.

287
Q

How does lossy compression reduce file size?

A

By throwing out some of the data - this is irreversible.

288
Q

Why is lossy compression unsuitable for text or program files?

A

File size is reduced by throwing out data - a book with missing letters would be unreadable, a program with missing letters/formatting would be inexecutable

289
Q

Why is lossy compression more useful for graphic and audio files?

A

Because they contain lots of information that can be discarded.

290
Q

What are RAW files?

A

Image files that have not been compressed and which contain all of the colour data are called RAW files.

291
Q

True or false: RAW in RAW files is an acronym.

A

False. RAW is not an acronym, it just means that the files is as it was when produced by a camera sensor and has not been compressed in any way.

292
Q

What exactly happens during lossy compression? HINT: WHAT DOES THE ALGORITHM DO?

A

The algorithm analyses the image and finds areas where there are only slight differences that we might not be able to distinguish. It then gives these the same value so that it can rewrite the file using fewer bits.

293
Q

What does JPEG stand for?

A

Joint Photographic Experts Group - known for ‘.jpeg’ files.

294
Q

What does WAV stand for?

A

Waveform Audio Format - known for ‘.wav’ audio files.

295
Q

What are WAV files?

A

Digital audio files that contain all of the sound data.

296
Q

How many MB would generally be in a 3 minute WAV file?

A

30 MB WAV file

297
Q

How many MB would generally be in a 3 minute MP3 file?

A

3 MB MP3 file

298
Q

How large is a WAV file compared to an MP3 file?

A

MP3 files are often about 1/10th the size of WAV files.

299
Q

What do computer networks enable? Give at least 2 examples of possible uses. HINT: ANSWER GIVES 5.

A

Computer networks allow computers and devices to share data. This includes:
1. computer-to-computer communication
2. mobile phone networks
3. computers communicating with devices such as printers, mice and keyboards
4. smart televisions
5. tablets and media players downloading videos and music and playing them through external devices such as speakers and digital projectors.

300
Q

What does LAN stand for?

A

Local Area Network

301
Q

When are LANs used?

A

Computers in a site such as an office building use an LAN to connect with each other.

302
Q

What is a LAN?

A

An LAN is a computer network for data transmission within a small geographical area such as a home, office or school or a group of buildings on a site.

303
Q

What does WAN stand for?

A

Wide Area Network

304
Q

When are WANs used?

A

WANs are used for connecting LANs over a large geographical area.

305
Q

What is a WAN?

A

A WAN is a network that connects separate LANs over a large geographical area. This ensures that computers in one location can communicate with computers and users in other locations.

306
Q

True or false: The internet is a huge WAN.

A

True.

307
Q

What are the two network types?

A

Client-server networks and peer-to-peer networks

308
Q

When are peer-to-peer networks used?

A

Peer-to-peer networks are used to connect a small number of devices, for example in a home or office where there are just a few users.

309
Q

Give two advantages of peer-to-peer networks:

A
  1. easier to set up and maintain
  2. cheaper
310
Q

Give two disadvantages of client-server networks:

A
  1. more expensive to set up and maintain as a more powerful computer is required to act as the server and network software is required
  2. specialist knowledge is needed to administer the network
311
Q

In client-server networks, what are the servers?

A

The computers that control access to the network.

312
Q

In client-server networks, what are the clients?

A

The computers on which the users work - computers that act as a desktop for the users and which relies on a server for its operations.

313
Q

Explain how a client-server network works.

A

In a client-server network there are two types of computers: the computers that control access to the network (servers) and the computers on which the users work (clients).
From the client machines, the users log into the network servers in order to be able to access programs and peripherals to save data on the servers.
The server is therefore responsible for the security of the network, expecting users to log in with a username and password. As all files are stored on the server the data can be backed up centrally.

314
Q

True or false: In a peer-to-peer network, all computers are equal.

A

True. The computers are simply connected together without any one computer having superiority over the others.

315
Q

Explain how a peer-to-peer network works.

A

In a peer-to-peer network, the computers are simply connected together without any one computer having superiority over the others. All of the computers on a peer-to-peer network are equal.
Through sharing rights granted by the users any computer can share thee programs of another, save data onto their hard disk and use printed connected to them.
Each computer acts as both a client and a server and can communicate directly with all of the others.
Security is distributed and the users of each computer have to be able to grant access rights to its resources and allot passwords.
As data is stored on all f

316
Q

Explain how a peer-to-peer network works.

A

In a peer-to-peer network, the computers are simply connected together without any one computer having superiority over the others. All of the computers on a peer-to-peer network are equal.
Through sharing rights granted by the users any computer can share thee programs of another, save data onto their hard disk and use printed connected to them.
Each computer acts as both a client and a server and can communicate directly with all of the others.
Security is distributed and the users of each computer have to be able to grant access rights to its resources and allot passwords.
As data is stored on all of the computers and is not held centrally, all the users are responsible for backing up procedures.

317
Q

What does a computer need to connect to a network?

A

A computer needs some hardware and also some software that allows it to communicate with the other computers.

318
Q

What are the most commonly used cables to connect devices?

A

Twisted pair cables

319
Q

What are twisted pair cables?

A

Cables in which pairs of copper wires are twisted together and carry electrical signals.

320
Q

What are optical fibre cables made of?

A

Glass

321
Q

What are microwaves in computer science?

A

Electromagnetic waves that can be used to carry data between computers.

322
Q

What are protocols?

A

Agreed rules for requesting and sending data across networks.

323
Q

What is the motherboard?

A

The main printed circuit board of the computer; it has connectors that other circuit boards can be slotted into.

324
Q

What are optical fibre cables?

A

Cables which are made of glass and transmit information encoded in beams of light. They are much faster than twisted pair cables at transmitting data.

325
Q

What does NIC stand for?

A

Network Interface Card

326
Q

What is the NIC (Network Interface Card) also known as?

A

Network adapter

327
Q

What does the NIC/Network adapter do?

A

It is a component that connects a computer to a network. It formats the data sent from the computer into a required format according to the protocols (rules) of the network.

328
Q

Where is the NIC built into?

A

The motherboard

329
Q

True or false: NICs support both wireless and wired connections.

A

True

330
Q

What does MAC stand for?

A

Media Access Control

331
Q

Every NIC is created with a hardware number permanently burned into it. What is this called?

A

The MAC (Media Access Control) address.

332
Q

What is the purpose of a MAC address?

A

Every MAC address is unique so that all data on a network can be sent to the correct component . MAC addresses are 48 bits in length, usually displayed as a 12-digit hexadecimal number.

333
Q

What do network switches allow?

A

Network switches allow individual devices to connect to a network using cables.

334
Q

How do network switches work? HINT: 5 POINTS

A
  1. all of the computers on a network plug into a port on the switch using a cable.
  2. switches read the messages passing through them.
  3. they can read the destination addresses and send them to only the intended computers.
  4. they can do this because they build up a table of MAC addresses on the network to cut down on unnecessary network traffic.
  5. switches can send and receive information at the same time.
335
Q

What is network traffic?

A

The overall network usage caused by all of the data that is being transmitted at a given time.

336
Q

What do computers need an NIC or network adapter for?

A

To connect to a network.

337
Q

What are switches used for?

A

To allow messages to be transmitted between computers in a single network.

338
Q

What are routers used for?

A

To transmit messages between computers on different networks.

339
Q

Give two ways to carry data across a network:

A
  1. cables
  2. radio waves
340
Q

Why are routers similar to switches?

A

Routers and switches both read the address information and forward the messages to the correct network. A switch does this within a single network, but a router does this across several networks.

341
Q

What are routers commonly used for in the home?

A

Routers are commonly used in the home to allow many computers to access one internet connection. The router links the home network to the Internet. The router will transmit the incoming web pages, streamed audio, etc. to the correct computer on the network.

342
Q

What does WAP stand for?

A

Wireless Access Point

343
Q

What do wireless access points allow?

A

Wireless access points allow wireless devices to connect to a wired network.

344
Q

How do wireless access points work?

A

Wireless access points convert data they receive through cables into a wireless signal (and vice versa) to allow wireless devices to connect to a wired network.

345
Q

True or False: Wireless access points can direct messages to particular devices

A

False. Unlike switches, they CANNOT direct messages to particular devices.

346
Q

What is a web server?

A

A computer that can serve world wide web pages to other computers that request them.

347
Q

What is the Ethernet?

A

A set of technical standards for connecting computers.

348
Q

What is frequency?

A

The number of waves per second.

349
Q

What is Wi-Fi?

A

A set of technical standards or protocols for short-range connection of digital devices using radio waves.

350
Q

What is bluetooth?

A

A set of technical standards or protocols for short-range connection of digital devices using radio waves.

351
Q

What is bandwidth?

A

Bandwidth is the amount of data that can pass through a transmission medium per second.

352
Q

What is bandwidth measured in?

A

Bits per second (bps) or megabits per second (Mbps) - bandwidth is a measure of how many bits can get through a particular point in a second.

353
Q

How does a copper wire carry data?

A

Copper wires carry the data as electric currents.

354
Q

How does a fibre optic cable carry data?

A

Fibre optic cables transmit data as pulses of light generated by a LED or laser.

355
Q

What does LED stand for?

A

Light Emitting Diode

356
Q

Name 3 advantages of fibre optic cables over copper wire cables:

A
  1. Far greater bandwidth
  2. Can carry signals much faster
  3. Can travel over greater distances without needing to be boosted
357
Q

True or False: Radio waves are a type of microwave.

A

True.

358
Q

What do microwaves consist of?

A

Electromagnetic radiation travelling in waves with a frequency higher than 1 GHz.

359
Q

Radio waves can transmit data across networks in what range of frequencies?

A

Radio waves are used to transmit data across networks in frequencies of between 2.4 and 5 GHz.

360
Q

What is The Internet?

A

The Internet is a global system of interconnected computer networks which serves billions of users worldwide - this makes it a wide area network.

361
Q

Name 2 services The Internet provides:

A
  1. Email
  2. World Wide Web (www)
362
Q

Who first proposed the World Wide Web?

A

British scientist, Tim Berners-Lee

363
Q

When was the World Wide Web proposed by Tim Berners-Lee?

A

1989

364
Q

When was the first website launched?

A

Time Berners-Lee launched the first website in 1990.

365
Q

What is a host?

A

A host is a computer which can be accessed by users working at remote locations using networks, including the internet.

366
Q

What do web hosting companies do?

A

Web hosting companies rent space on their servers where people can develop their own websites that can be accessed by users all over the world using the World Wide Web.

367
Q

How many host computer systems were there in 1969?

A

4 - today there are 10s of millions.

368
Q

When was The Internet Society established?

A

1992

369
Q

Why was The Internet Society established?

A

It was established to oversee the policies and protocols that define how we use and interact with the Internet.

GCSE Revision Flashcards (24 decks)

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