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Computer Science > AS Units > Flashcards

AS Units Flashcards

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1
Q

What is a digital certificate?

A

A document used to prove ownership of a public key

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2
Q

What is a digital certificate used for?

A

To prove the authenticity and legitimacy of a digital certificate

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3
Q

What does a digital certificate contain?

A

A digit signature, the subject of the key, and information about the key.

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4
Q

What is the big-O of a linear search?

A

O(n)

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5
Q

What is the big-O of a binary search?

A

O(log n)

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6
Q

What is the big-O of a bubble sort?

A

O(n^2)

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7
Q

What is the big-O of a mergesort?

A

O(nlog n)

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8
Q

What is a cancellation error?

A

An error that occurs when performing mathematical operations on very large or very small numbers, causing an error to occur.

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9
Q

What is underflow?

A

An error that occurs when a number is too small to be represented using a certain number of bits.

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10
Q

What is overflow?

A

Overflow occurs when a number is too big to be represented using a certain number of bits.

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11
Q

Give details of the fetch part of the fetch-decode-execute cycle.

A

×The contents of the program counter are transferred to the memory address register (MAR)
×The address bus is used to retrieve the instruction stored at the address location specified by the MAR in main memory
×The instruction is stored in the memory buffer register (MBR)
×The program counter is incremented
×The contents of the MBR are moved to the current instructions register (CIR)

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12
Q

Give details of the decode part of the fetch-decode-execute cycle.

A

×The instruction is decoded by the control unit

×The instruction is split into an opcode and operands

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13
Q

Give details of the execute part of the fetch-decode-execute cycle.

A

×Any necessary data is retrieved from memory

×The instruction is executed and the results are stored in the accumulator

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14
Q

What is a thin client?

A

A computer that relies mostly on a server to operate properly. They have weak hardware and software specifications, with the server conducting most data processing

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15
Q

What is a thick client?

A

A client that has more robust hardware and software, relying on the server mostly for storage facilities

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16
Q

What are the advantages of using thick clients?

A

×A less powerful​ server is needed

×The network has a better uptime

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17
Q

What are the advantages of using thin clients?

A

×Cheaper client computers are available

×Network administrators can better manage accessibility

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18
Q

What is the purpose of a firewall?

A

To prevent unauthorised access to a network

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19
Q

What is packet filtering?

A

Packet filtering prevents packets of data with specific port numbers from bypassing the firewall, stopping potentially malicious data from entering the network

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20
Q

What are proxy networks?

A

Proxy networks are networks that allow the true source of data to be masked, instead giving a false source through which the data has been routed.

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21
Q

What is stateful inspection?

A

Stateful inspection monitors the activity of the source network of a packet, and is used to determine the legitimacy of the data.

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22
Q

What are parity bits?

A

Parity replace the most significant bit of a byte and allow for an odd number of errors to be detected after transmission

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23
Q

How does even parity work?

A

The number of 1s in the byte are counted. If there are an even number of 1s, the even parity is set to 0. Otherwise, the parity but is set to 1.

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24
Q

How does majority voting work?

A

Each bit in a byte is sent an odd number of times. The instance of a bit that occurs most often is used when reassembling the byte at its destination

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25
Q

What is application software?

A

Any software that a user can run and interact with

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26
Q

What is utility software?

A

Software that maintains and manages a computer system

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27
Q

What is the purpose of an assembler?

A

An assembler translates assembly language into machine code

28
Q

What is bytecode?

A

Intermediate code produced by a compiler that allows for code to be run on a virtual machine. Java is a good example of a language that produced bytecode

29
Q

What is an operating system?

A

An operating system is a virtual machine used to hide the complexities of hardware from a user. It handles memory + resource management, and virtual machines

30
Q

What is scheduling?

A

Scheduling allows for parallel execution to be simulated on a single-core processor by allocating a specific length of time to the execution of each running program

31
Q

What is a worm?

A

A form of standalone malware that reproduces itself in order to do harm to a network

32
Q

What is a virus?

A

Malware that is designed to damage files on a computer

33
Q

What is a Trojan horse?

A

Malware that misleads a user into installing it in order to allow for things like backdoors to be set up

34
Q

How does symmetric encryption work?

A

Both the sending and receiving device have access to a public key which is used to encrypt plaintext and decrypt ciphertext

35
Q

How does asymmetric encryption work?

A

The receiving device generates a long, random string of characters from a private key that is sent to the sending device. The sending device encrypts the data using the public key, which can then only be decrypted by the receiving device

36
Q

What does the arithmetic logo unit do?

A

Carries out integer, floating point, and bitwise arithmetic

37
Q

What does the control unit do?

A

Manages and coordinates data flow and the operations of the CPU

38
Q

What is a clock cycle used for?

A

To keep processor functions synchronised

39
Q

What is the program counter?

A

A special-purpose register used to store the address in memory of the next instruction to be executed by the processor

40
Q

What is the status register?

A

A special-purpose register used to tell the processor if overflow, underflow, or other errors occur during operations

41
Q

How does increasing the word size of a CPU improve performance?

A

More bits can be processed by the CPU at once

42
Q

How does using a larger address bus improve performance?

A

More memory locations can be accessed per request, so data can usually be accessed faster

43
Q

When does an interrupt occur?

A

When a program has been terminated or requests services from the operating system

44
Q

What happens when an interrupt occurs?

A

Execution of the current process is suspended. The value of each register is stored in the system stack. An Interrupt Service Routine is called to handle the interrupt. The system stack is restored and processing continues

45
Q

When is an interrupt checked for?

A

At the end of each FDE cycle

46
Q

What are the attributes of an object?

A

The characteristics an object has

47
Q

What is the state of an object?

A

The value the object returns

48
Q

What is the behaviour of an object?

A

The functions that an object can perform

49
Q

What is instantiation?

A

The process of creating a new instance of an object

50
Q

What is a reference-type variable?

A

A data type that refers to an instance of an object

51
Q

What are setters and getters?

A

Setters are used to assign a state to an object. Getters are used to return the state of an object

52
Q

What is encapsulation?

A

The process of holding the state, behaviours, and methods of am object together.

53
Q

What is the advantage of using encapsulation?

A

It allows for classes to interact with each other without having to worry about data flow as much

54
Q

What is association?

A

Association is the term used to describe the fact that an object “has an instance” of another object. E.g. A hotel has a room

55
Q

What is inheritance?

A

A way of describing that an object is also another object. E.g. A rabbit is an animal

56
Q

What is association aggregation?

A

A way of describing the fact that an object is an instance of another object, but is it destroyed if the second object gets destroyed

57
Q

What is composition aggregation?

A

A way of describing that an object has another instance of an object, but cannot exist without the second object

58
Q

What is polymorphism?

A

The ability of an object to override a method of an inherited class

59
Q

Why is composition preferred over inheritance?

A

Completion is a more rigid relationship than inheritance

60
Q

What are access modifiers?

A

Ways of controlling which parts of a script can access an object variable

61
Q

What is a private variable?

A

A variable that can only be accessed by code within the class the variable was defined within

62
Q

What is a protected variable?

A

A variable that only subclasses of an object can access

63
Q

Describe the structure of an HDD.

A

An HDD contains metal platters coated in a ferrous substance. These particles can be polarised north / south by read/write heads to represent 1s or 0s

64
Q

List advantages and disadvantages of HDDs

A

They are less portable, and can be damaged if the disk is moved during use
They have large storage capacities and are relatively cheap

65
Q

How do optical disks work?

A

A high-powered laser is used to burn the surface of the disk, changing its reflective properties. Pits are less reflective than lands, so both can be used to represent a 1 or 0

66
Q

How do read/write DVDs work?

A

They are coated with phase-changing alloys, so that their state changes depending on the power of the laser used

67
Q

List the advantages and disadvantages of using optical disks

A

They are light and cheap to produce

Can be damaged by scratches or sunlight

Computer Science (8 decks)

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