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2022 - Computer Science A Level AQA > 6 - Fundamentals of Computer Systems > Flashcards

6 - Fundamentals of Computer Systems Flashcards

1
Q

Describe the roles of the four types of system software.

A

Describe the roles of the four types of system software.

Operating system - Provides a user interface between the user and the hardware, runs application programs and manages hardware resources.

Utility programs - Programs designed to help maintain the computer. Examples include virus scanner or file managers.

Library programs - Collections of resources used to develop software. They include pre-written code and subroutines.

Translators - Converts source code into machine code. An assembler converts assembly code into machine code, a compiler converts source code written in a high level language into machine code and an interpreter treats high level language source code as data and interprets that data as instructions to its own routine.

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2
Q

What are utility programs?

A

Software that is used to support the efficient running of a computer system. Utility programs can be part of the OS or installed separately. Typically, utility programs perform maintenance, analysis, configuration, and optimisation tasks.

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3
Q

State one purpose of library programs.

A
  • To allow sharing of run-time code across programs.
  • To save memory as routines are only loaded when needed.
  • To provide access to procedures/functions when writing a program.
  • To reduce the time taken to write a program.
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4
Q

State one purpose of the operating system.

A
  • Provide an interface between the computer and the user.
  • To manage devices/files/memory.
  • To provide a virtual machine.
  • To provide a software platform on which other programs can run.
  • To hide the complexity of the hardware from the user.
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5
Q

What is the difference between application software and system software?

A

Application software is used to perform tasks that the user would have to do if they didn’t have a computer.
System software is a layer of software which enables users to operate the computer and is used in the management of a computer system.

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6
Q

Are Operating Systems classified as system software or application software?

A

System Software because it is required for the functioning of the system itself.

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7
Q

What types of resource management is an operating system responsible for?

A
  • Processors.
  • Input / Output Devices.
  • Main Memory.
  • Storage.
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8
Q

How does the OS manage processors?

A

The OS is responsible for scheduling processes for programs that are running and allocating them processor time.

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9
Q

How does the OS manage I/O devices?

A

The OS allocates I/O devices to different processes and manages the communication between these processes and devices.

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10
Q

How does the OS manage memory?

A

The OS keeps track of what portions of memory have been allocated; determines how much memory to allocate to each process and determines when a portion of memory should be available for a process.

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11
Q

How does the OS manage storage?

A

The OS will allocate space on a storage device to files, organise files into directories and determine where on the device to save a file. All of these features are part of a filesystem. The OS will also manage which processes / users can access different files and directories.

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12
Q

What is a low-level language?

A

A low-level language is a language that is very similar to the instruction set of the computer.

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13
Q

Most computer programs are initially written in an imperative high level language rather than assembly language.
Explain why this is the case.

A
  • High level languages are problem oriented.
  • High level languages are platform independent.
  • High level languages have English like keywords.
  • High level languages are less tedious to program as there is a one to many mapping of HLL statements to machine code commands.
  • High level languages are easier to write, understand and debug the code.
  • High level languages offer extra features such as data structures.
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14
Q

What are the advantages of writing a program in assembly language over writing a program in machine code?

A
  • Easier to understand.
  • Takes less time to code.
  • Fewer mistakes made in coding.
  • Ability to add comments to code.
  • Use of symbolic name for operands.
  • Use of labels.
  • Easier to maintain/debug.
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15
Q

Why are there so many high level programming languages?

A
  • Languages used for a specific problem type.
  • Access to specific data types.
  • Providing different function libraries.
  • Languages developed for specific hardware.
  • Languages developed for visual applications.
  • Competition between different companies who develop languages.
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16
Q

Some high level languages are imperative. Explain the term imperative.

A

Imperative high level language programs define sequences of commands for the computer to perform. Imperative high level languages describe how to solve a problem.

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17
Q

Explain the advantages and disadvantages of programming using imperative high level languages compared with low level languages.

A

Advantages:
• Programs written in a high level language are machine independent.
• People find it easer to debug high level language programs.
• People find it easier to read, write and understand high level language program code.
• High level languages save time for programmers as they use fewer lines of program code.

Disadvantages:
• Programs written in a high level language may not make best use of specific features of a particular processor.
• Programs written in a high level language may not execute as quickly.
• Programs written in a high level language may use more memory.

18
Q

What features of high level programming languages make high level language programs easier to understand.

A
  • Use of meaningful identifier names.
  • Use of indentation to separate out statement blocks.
  • Use of comments to annotate the program code.
  • Use of procedure, functions and sub-routines.
  • Use of constants.
19
Q

What is the symbol for a NOT gate?

Construct the truth table for a NOT gate.

A

─▷∘─

A Q
0 1
1 0

20
Q

What is the symbol for an AND gate?

Construct the truth table for an AND gate.

A

═D─

A  B  Q
0  0  0
0   1  0
1   0  0
1    1   1
21
Q

What is the symbol for a NAND gate?

Construct the truth table for a NAND gate.

A

═D∘─

A  B  Q
0  0   1
0   1   1
1   0   1
1   1    0
22
Q

What is the symbol for an OR gate?

Construct the truth table for an OR gate.

A

https://www.google.com/url?sa=i&url=https%3A%2F%2Fcommons.wikimedia.org%2Fwiki%2FFile%3AOr-gate-en.svg&psig=AOvVaw1Y4Lw3IFkCvmyh_Z1pLRg8&ust=1650825187166000&source=images&cd=vfe&ved=0CAwQjRxqFwoTCODJuprpqvcCFQAAAAAdAAAAABAJ

A  B  Q
0  0  0
0   1   1
1   0   1
1    1   1
23
Q

What is the symbol for an XOR gate?

Construct the truth table for an XOR gate.

A

https://www.computerscience.gcse.guru/wp-content/uploads/2016/11/XOR-350x175.png

A  B  Q
0  0  0
0   1   1
1   0   1
1    1  0
24
Q

What is the symbol for a NOR gate?

Construct the truth table for a NOR gate.

A

https://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/NOR_ANSI_Labelled.svg/1200px-NOR_ANSI_Labelled.svg.png

A  B  Q
0  0   1
0   1   0
1   0   0
1    1   0
25
Q

What is the Boolean expression for a NOT gate?

A

Q = A̅

26
Q

What is the Boolean expression for an AND gate?

A

Q = A . B

27
Q

What is the Boolean expression for an OR gate?

A

Q = A + B

28
Q

What is the Boolean expression for an XOR gate?

A

Q = A ⊕ B

29
Q

What is the Boolean expression for a NAND gate?

A

Q = A̅ ̅.̅ ̅B̅

30
Q

What is the Boolean expression for a NOR gate?

A

Q = A̅ ̅+̅ ̅B̅

31
Q

What are the three Boolean algebra laws?

A

• Commutative
A . B = B . A

     A + B = B + A
• Associative
     A . (B . C) = (A . B) . C
     A + (B + C) = (A + B) + C    
• Distributive
     A . (B + C) = A . B + A . C
     A + B . C = (A + B) . (A + C)
32
Q

What are the Boolean identities for OR?

A

0 + A = A
1 + A = 1
A + A = A
A + A̅ = 1

33
Q

What are the Boolean identities for AND?

A

0 . A = 0
1 . A = A

A . A = A
A . A̅ = 0

34
Q

How do you simplify Boolean expressions using the identities?

eg. A . B + A . B̅

A
  • Factorise or expand the brackets.
  • Use identities

A . B + A . B̅
A . (B + B̅)
A . 1
A

35
Q

What is De Morgan’s Law?

A

“Break the line, change the sign”

A̅ ̅.̅ ̅B̅ = (A̅ + B̅)
(̅A̅ ̅+̅ ̅B̅)̅ = A̅ . B̅

36
Q

How do you simply Boolean expressions using De Morgan’s Law?

eg. A̅ + A̅ ̅+̅ ̅B̅

A
  • Use De Morgan’s Law.
  • Factorise or expand the brackets.

• Use identities.

A̅ + A̅ ̅+̅ ̅B̅
A̅ + A̅ . B̅
A̅ . (1 + B̅)
A̅ . 1
A̅
37
Q

Explain the general purpose of a D-type flip-flop.

A

Used to store state of data input.

38
Q

What is a D-type flip-flop used for?

A

The state of input data is stored and the output is updated to reflect the current status of the input.

39
Q

What are the inputs of a D-type flip-flop?

A
  • Data

* Clock

40
Q

What is the role of an Operating System?

A
  • To hide the complexities of the hardware from the user so that the user is presented with a machine that is much easier to use.
  • To manage the hardware resources to give an orderly and controlled allocation of the processors, memories and I/O devices among the various processes competing for them, and manage data storage.
41
Q

What are the limitations of using assembly language to code a program?

A
  • Very difficult to understand
  • Very easy to make mistakes
  • Hard to find mistakes in the code
  • Time consuming to develop software in assembly language
  • Lack of portability
  • Lack of in-built functions

2022 - Computer Science A Level AQA (11 decks)

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