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A Level Computer Studies > Unit 5 - Computer Organisation and Architecture > Flashcards

Unit 5 - Computer Organisation and Architecture Flashcards

1
Q

What is a computer system?

A

Any system that can take a set of inputs and process them to produce useful outputs

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2
Q

Why is an I/O controller required in a computer?

A

This is necessary because the processor cannot communicate directly with peripheral devices

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3
Q

How does the I/O controller work?

A

The I/O controller converts the signals sent by the peripherals into a format which the processor can understand and vice versa

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4
Q

What piece of software works in unison with the I/O controller?

A

A device driver

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5
Q

What does the device driver do?

A

A device driver is a piece of software that allows peripheral devices to communicate with the processor. The component of the processor is communicates with is the I/O controller.

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6
Q

Busses are made up of _______

A

Microscopic parallel wires

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7
Q

What are the 4 standard bus sizes

A

8, 16, 32 or 64 lines

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8
Q

T/F: the control bus is omnidirectional

A

True

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9
Q

What does omnidirectional mean?

A

Signals can be sent in both directions

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10
Q

What is the control bus used for?

A

Controls the flow of data between the processor and other parts of the comput

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11
Q

T/F: you can only send signals in one direction on the data bus

A

False: the data bus is omnidirectional

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12
Q

What impact will increasing the width of the data bus have on the computer?

A

It will increase the performance of the computer because the more wires there are in the data bus the more bits can be sent at once

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13
Q

Which two busses are omnidirectional?

A

The control and data bus

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14
Q

Which bus is unidirectional?

A

The address bus

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15
Q

What is the address bus used for?

A

It sends memory addresses from the processor to CPU components

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16
Q

What does the width of the address bus determine?

A

The maximum number of memory addresses of that system because a memory address is sent in one operation

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17
Q

What are the 5 main control signals?

A
  1. Memory read
  2. Memory write
  3. Bus request
  4. Bus grant
  5. Clock
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18
Q

What do the control signals memory read and memory write do?

A

Memory read causes data from the addressed location to be placed on the data bus
Memory write causes data from the data bus to be written into the addressed location

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19
Q

What do the control signals bus request and bus grant do?

A

Indicates that a device is requesting use of the data bus
Indicates that the CPU has granted a device access to the data bus

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20
Q

What does the control signals clock do?

A

Synchronises operation

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21
Q

What is the word length?

A

The number of bits that can be addressed, transferred or manipulated as one unit

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22
Q

What is stored in main memory?

A

Data and instructions

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23
Q

What is a general purpose computer?

A

A computer that can perform many different tasks at different times

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24
Q

What is the fixed program concept?

A

This described the programming of early computer when they only had one program which meant that they could only do one thing

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25
Q

What is the stored program concept?

A

The idea that instructions are stored together in main memory so they can be accessed easily by the processor

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26
Q

What is the difference between Von Neumann and Harvard architecture?

A

In the von Neumann architecture instructions and data are stored in the same memory where as they have different memories in the Harvard architecture

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27
Q

T/F: the von Neumann architecture is viewed as better than the Harvard architecture

A

False: the Harvard architecture is viewed as superior because it allows for different word lengths and memory capacity for the two different types of information

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28
Q

Why is the von Neumann architecture more commonly used?

A

The Harvard architecture is more costly and is very complex to program as well as requiring more physical space

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29
Q

What happens during the Fetch-Decode-Execute cycle?

A
  1. Address of next instruction transferred from PC to MAR
  2. PC incremented by 1
  3. Instruction stored in location addressed by MAR is transferred to MBR
  4. Instruction transferred from MBR to CIR
  5. Instruction in the CIR gets decoded by the CU and split into the opcode and operand
  6. Additional data, if required by the instruction, is fetched from the memory
  7. Additional data passed to registers
  8. Instruction executed by the ALU
  9. Registers are used to store intermediate data or results
  10. Result is stored in the accumulator or general purpose register or memory
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30
Q

What are the 6 main dedicated registers and their purpose?

A

Program Counter: holds the memory address of the next instruction to be executed, located in the CU
Current Instruction Register: holds the instruction that is currently being decoded or executed
Memory Address Register: Holds the address of the memory location that the processor has to fetch or store data from or in
Memory Buffer Register (aka Memory Data Register): Temporarily holds data moving between the processor and main memory
Status Register: holds information about the current state of operations, sets flags and detects error conditions
Interrupt register: Stores details of incoming interrupts

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31
Q

What factors effect the performance of a computer system?

A

Clock speed, cache memory, number of cores, word length and address and data bus width

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32
Q

What are the sub-components of the processor?

A

ALU, CU, Clock, General Purpose Registers and Dedicated Registers

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33
Q

What does the processor do?

A

Controls, calculates and executes instructions

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34
Q

What does the ALU do?

A

Performs, arithmetic, logic and sift operations and acts as the problem-solving component within the processor

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35
Q

What does the CU do?

A

Coordinates and organises the processor through the utilisation of the fetch-decode-execute system and synchs each step with a pulse from the clock

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36
Q

What do general purpose registers do?

A

Temporarily stores results from the ALU before they need to be used

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37
Q

What is the accumulator?

A

A replacement for the general purpose registers, it is a register that it specifically for temporarily storing results from the ALU

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38
Q

What do dedicated registers do?

A

Hold specific data

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39
Q

What does the clock do?

A

Synchronises when instructions are executed, it controls the speed at which the processor works. Instructions are generally executed on the rising edge of the clock and different instructions will take a different number of cycles to complete.

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40
Q

What is an instruction set?

A

The different commands which the processor can perform

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41
Q

Why do different processors have different instruction sets even if they perform the same instructions?

A

They have different ways of expressing instructions

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42
Q

What are the 6 different types of instruction?

A
  1. Data transfer .e.g. LOAD or STORE
  2. Arithmetic operations .e.g. ADD or SUBTRACT
  3. Comparison operations
  4. Logical operations .e.g. AND, OR or NOT
  5. Branch, conditional and unconditional
  6. Shift operations, shifting bits left and right
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43
Q

What language does the processor understand?

A

Machine code

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44
Q

What are the two parts of an instructions?

A

The opcode and the operand

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45
Q

What is the opcode?

A

The section of the instruction which dictates the command which the processor must execute

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46
Q

What is the operand?

A

The section of the instruction which provides the information the processor is to use to execute the command given in the opcode

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47
Q

What is immediate addressing?

A

This is when the information to be used in the command is given in the operand

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48
Q

What is direct addressing?

A

This is when the memory address of the data to be used in the command in given in the operand

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49
Q

What is the addressing mode?

A

The section of the opcode (often two bits) which indicates what type of addressing the command is using and whether it is immediate or direct

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50
Q

What method of expressing information does assembly language use?

A

Mnemonics

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51
Q

What section of the instruction does the mnemonic represent in assembly language?

A

The opcode

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52
Q

What character is used to indicate a comment in assembly language?

A

;

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53
Q

What type of storage is volatile?

A

Primary storage

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54
Q

What type of storage is non-volatile?

A

Secondary storage and Main Memory

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55
Q

Define processor

A

A device that carries out computation on data by following instructions in order to produce an output

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56
Q

Give the simplest explanation of main memory?

A

Stores data and instructions that will be used by the processor

57
Q

What is a chip?

A

An electronic component contained within a thin slice of silicon

58
Q

What physical component make up RAM?

A

Chips

59
Q

What physical component comprises the RAM?

A

A thin slice of silicon implanted with millions of transistors that are connected by busses

60
Q

What do transistors do?

A

Control the flow of electrical pulses that are sent in time with the clock

61
Q

What is another name for ROM?

A

Main Memory

62
Q

Where are the instructions for computer start up stored?

A

ROM

63
Q

What is the difference between RAM and ROM?

A
  1. ROM cannot be written to unless it is programmable ROM where as RAM can
  2. RAM is volatile meaning it will not store any information once the computer is switched off whereas ROM does
64
Q

What is addressable memory?

A

Memory made up of millions of addressable cells that each have a unique identifier

65
Q

Why is it beneficial for the width of the data bus to be the same as the word length of the computer?

A

All data units can be sent in one operation

66
Q

What is the memory word length?

A

The smallest unit of addressable memory in a computer system

67
Q

What two components does the address bus connect?

A

Main memory and the processor

68
Q

Describe the concept of addressable memory

A

The concept that data and instructions are stored in memory using discrete addresses

69
Q

What is the role of physical ports on a computer?

A

They allow I/O devices to be connected

70
Q

What is the I/O controller an example of?

A

An interface

71
Q

What are the two roles of an I/O controller?

A

They translate signals from peripheral devices into the format required by the processor and act as a buffer for data being sent from the device to a the processor as it works at a much slower speed than the processor

72
Q

What does the word architecture refer to in computer science?

A

The way in which something is built

73
Q

What is the hardware difference between the von Neumann and Harvard architecture?

A

The way in which the chip is constructed

74
Q

What type of computer system is the Harvard architecture more commonly used on?

A

Embedded systems .e.g. mobile phones or burglar alarms

75
Q

What is digital signal processing?

A

DSP is a process that takes continuous real world data and compresses it to allow for faster processing

76
Q

Why are chips optimised for DSP often used in mobile phones?

A

They have low power consumption which is necessary for mobile phones

77
Q

Describe the fetch section of the fetch-execute cycle in one sentence

A

The processor retrieves the program’s next instruction from an addressable memory slot which will be in machine code

78
Q

Describe the decode section of the fetch-execute cycle in one sentence

A

The processor determines what the machine code instruction is telling it to do

79
Q

Describe the execute section of the fetch-execute cycle in one sentence

A

The processor will carry out the instruction

80
Q

How does the clock speed affect the performance of a processor?

A

It determines the number of clock cycles that occur per second which affects the number of instructions that are be executed by the processor per second

81
Q

How does the bus width affect the performance of a processor?

A

The width of the data bus dictates how many bits can be sent in one operations and the width of the address bus dictates the number of addressable memory locations

82
Q

How does the word length affect the performance of a processor?

A

The word length dictates the maximum number of bits that can be manipulated with one pulse of the clock

83
Q

How does the number of cores affect the performance of a processor?

A

The term core defines the components that allow the fetch-execute cycle to occur so having multi-core system means you have more than one processor on one chip which means that more instructions can be executed per second

84
Q

How does the cache memory affect the performance of a processor?

A

Cache memory can be accessed by the processor much faster than main memory can be so having more information stored in the cache memory means reduced latency when the processor wants to retrieve information

85
Q

What is an interrupt?

A

A signal sent by a device or program to the processor requesting its attention

86
Q

How does the processor check for an interrupt?

A

Between the end of each fetch-execute cycle and the start of the next the processor checks the contents of the interrupt register to see whether an interrupt has been sent

87
Q

What does the processor do if an interrupt has been sent?

A
  1. The processor pushes the current contents of the registers onto the system stack
  2. It will the look up what type of interrupt it is and the associated vector
  3. The processor will jump to the address specified by the vector
  4. The ISR will be run
88
Q

What is the Interrupt Service Routine (ISR)?

A

This is a routine which determines which routine is necessary to deal with the interrupt and then calls it (some are provided by device drivers for peripheral interrupts)

89
Q

How does the processor handle its current task when an interrupt is sent?

A

It pushes the current contents of the registers onto the system stack until the interrupt has been dealt with when it will pop them again and place them back in the appropriate registers to resume

90
Q

How does the processor deal with one or more interrupts at once?

A

It will assess the interrupts to determine which is more important and then deal with that one first .e.g. a printer will deal with an interrupt saying it is about to lose power before an interrupt saying that it is out of paper

91
Q

What is a vectored interrupt mechanism?

A

A method of handling interrupts by pointing to the first memory address of the instructions needed

92
Q

Describe why a vectored interrupt mechanism is necessary

A

Each interrupt has an associated memory address known as a vector that points to the starting address of the code associated with each interrupt in order for it to be run to deal with the interrupt

93
Q

Describe how a camera works

A
  1. The shutter opens and light is allowed to enter the lens
  2. The light is focussed by the lens through RGB filters to define colour
  3. Light is focussed on a sensor which is either a CCD or a CMOS
  4. The sensors consist of millions of transistors and each one holds data for one or more pixels
  5. As light hits the sensor it is converted to electrons and the amount of charge is recorded for each pixel
94
Q

What is a CCD?

A

Charge coupled device - a sensor in digital cameras that records the amount of light received and converts it into a digital value

95
Q

What is a CMOS?

A

Complementary Metal Oxide Semiconductor - a sensor in digital cameras that records the amount of light received and converts it into a digital value

96
Q

How do you define the capability of a digital camera?

A

You define a camera’s capabilities in terms of the number of megapixels that it uses to record images

97
Q

Define compression

A

The process of reducing the size of a file

98
Q

Define resolution

A

The number of pixels used to create an image

99
Q

What is a barcode reader?

A

A device that uses lasers or LEDs to read the black and white lines of a barcode

100
Q

How does a barcode scanner work?

A
  1. A light is passed over the barcode
  2. A sensor (such as a CCD or photodiode) measures the intensity of light being reflected back which is converted into current
  3. The waveform will represent the black and white areas of the barcode because they will reflect different amounts of light
  4. The waveform is converted from analogue into a digital binary representation
  5. This binary representation can then be interpreted by the software
101
Q

What is a UPC and how does it work?

A

Universal product code - has a series of black lines that can be 4 different widths and are encoded to represent the values 1 to 4. They also have numbers underneath them which are used as a manual override and include a check digit.

102
Q

How do EAN barcodes work for identifying food items?

A

EAN stands for European Article Number and each barcode number is present in a POS (point of sale) database that is used to identify the item

103
Q

T/F: QR codes are an iteration of barcodes

A

True

104
Q

How do QR codes differ from barcodes?

A

They consist of black and white blocks rather than lines, they can be read by a smartphone and can contain a wider range of information

105
Q

What is an RFID?

A

A microscopic device that stores data and transmits it using radio waves

106
Q

What is the most common use of an RFID?

A

Tracking items

107
Q

Describe how an RFID works

A
  1. The tag contains a chip which contains data about the item, a modem which modulates and demodulates the radio signals and an antennae
  2. Tags are either active or passive
  3. Tags can then receive and transmit signals
108
Q

Describe the logical difference between an active and a passive RFID

A

An active RFID will allow the user to always identify the location of the tag where as a passive RFID only allows the tag to be used when it is range of the RFID reader

109
Q

Describe the physical difference between an active RFID tag and a passive RFID tag

A

An active RFID tag has its own power source which is usually in the form of a small battery whereas a passive RFID tag uses electromagnetic waves transmitted by the reader as a power source

110
Q

What is the typical range of an RFID tag?

A

1m - 100m

111
Q

Give some real world examples of the applications of RFID tags

A
  1. Tracking individuals
  2. Electronic passports
  3. In cards to enable contactless payments
  4. School lanyards for singing in and out
  5. Tracking shipments and individuals
  6. Used to keep track of high value items in case they are stolen
112
Q

What is a laser printer?

A

A device that uses lasers and toner to create monochromatic and colour prints

113
Q

Describe how a laser printer works

A
  1. A rotating drum in the printer is coated with a chemical that has a negative charge
  2. A laser beam is reflected onto the drum and it discharges the area it is focussed on
  3. As the drum rotates it picks up toner which is attracted to the charged part of the drum
  4. Paper is passed over the drum and the toner is then attracted from the drum to the paper as it has an opposite charge
  5. Heat is used to fuse the toner to the paper
114
Q

How does a colour printer vary from a monochromatic printer?

A

A colour printer uses four different shades of toner which are cyan, yellow, magenta and key (black)

115
Q

What is a hard disk (HDD)?

A

A secondary storage device that us made up of metallic disks that store data magnetically

116
Q

Why are hard disks hermetically sealed?

A

To prevent the disks from being corrupted by dust or debris

117
Q

What is the physical composition of a hard disk?

A

There are several disks arranged in a stack with each having a read write head above it. The disks rotate and the heads move laterally meaning they can access any part of the disk

118
Q

How is storage on a hard disk organised?

A

The hard disk is split into sectors, each of which can be referenced by the OS. The sectors are arranged in concentric circles called tracks. The OS also groups sectors together into clusters which makes them easier to organise.

119
Q

What happens if a file only needs part of a cluster?

A

It will be allocated the whole cluster to make storage easier to organise

120
Q

What is the downside to clusters?

A

Because files will be allocated a whole cluster even if they don’t need it hard disks often have redundant space on them

121
Q

How do the heads read and write data from a hard disk?

A

The hard disk is coated in a magnetic coating which has areas of varying magnetism. A change in the direction of magnetism can be read as 1’s and 0’s

122
Q

What is the speed of a hard disk?

A

3600-12500rpm

123
Q

What is the typical capacity of a hard disk?

A

1Tb

124
Q

How does a read only optical disk work?

A

The disk has one track that starts in the middle and works its way to the edge in a series of concentric circles. The track consists of a series of pits and lands that are coated with a protective layer and a sensor reads how much light is reflected from the disk. This means that a laser is shone on the track of the disk and a pits of lands reflect light back to the sensor but a transition reflects the light so it misses the sensor. The amount of light reflected is read as an electrical signal and is then converted to binary

125
Q

How is a writeable optical disk constructed?

A

The disk is coated with a photosensitive dye that is translucent

126
Q

How do you write data to a writeable optical disk?

A

A laser alters the state of different dye spots by changing their density so that they become opaque

127
Q

How do you read data from a writeable optical disk?

A

A read laser reads the density of different areas on the optical disk based on the amount of light they reflect and these readings are interpreted as 1’s and 0’s

128
Q

What is a controller in an SSD?

A

The component that is needed to organise data into blocks for storage purposes

129
Q

What is a block in an SSD?

A

The concept of storing data into set groups of bits that have a fixed length

130
Q

What is a floating gate transistor?

A

A type of non-volatile transistor that stores data even without a power source

131
Q

How does an SSD work?

A

An SSD consists of programmable ROM chips that contain NAND memory. This means that it has blocks of NAND memory cells that consist of floating gate transistors which trap charge that is then interpreted as a 1 or a 0

132
Q

How does a floating gate transistor work?

A

It consists of two gates which are the floating gate and the control gate. The gates have an oxide between them which traps the charge even when the power is off.

133
Q

What are the advantages of SSDs?

A

The blocks means that it is very easy for the controller to locate specific memory cells and it also has a low latency because of this. They also have lower power consumption, are silent in operation and are not susceptible to damage. They also have less chance of mechanical failure than HDDs and their performance does not degrade over time as they do not require defragmentation.

134
Q

Detail the arrangement of data on a hard disk

A

Blocks contain fixed amounts of binary data. The blocks are then allocated to particular semiconductors in the disk. The semiconductors consist of floating gate transistors which hold the charge the represents the binary values in the blocks.

135
Q

Rank the three forms of secondary storage on latency

A

Low - SSD
High - HDD and optical disk

136
Q

Rank the three forms of secondary storage on capacity

A

High - HDD
Medium - SSD
Low - optical disk

137
Q

Why does clock speed have a limit?

A

Overclocking can cause the processor to overheat

138
Q

Define clock speed

A

The number of clock cycles performed per second (not the number of instructions because some instructions may take more than one clock cycle to complete)

A Level Computer Studies (15 decks)

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