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Computer Science > 4.6 Computer systems > Flashcards

4.6 Computer systems Flashcards

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1
Q

What is application software? Give 3 examples

A

Application software is designed to perform tasks a user wants to complete (user-oriented tasks), e.g. ⌨️word processors, 📊spreadsheet software, 🎥movie editing etc.

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2
Q

What is systems software?

A

Systems software is software used in the management of a computer system.

This comprises layers of software that abstract the user from how the computer works.

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3
Q

What is the operating system?

A

A collection of programs that control the operation of computer hardware and provide an interface between the user and the computer

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4
Q

What are utility programs? (2*)

A

Utility programs are systems software that is used to perform a non-core/ancillary/specific management function for a computer.

They help to manage or maintain a computer system but are not critical to the system.

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5
Q

2 ways utility programs can be installed

A

Utility programs can either be supplied with the operating system or installed at a later time.

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6
Q

4 types of system software

A

💻Operating System
🔧Utility Programs
📚Libraries
🈳Translators

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7
Q

3 examples of utility programs

A

antivirus software, defragmentation, compression

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8
Q

What are libraries? (2*)

A
  • Libraries are precompiled, pretested routines (sets of code) that other programs can link to and use
  • As long as the programmer includes a reference to the library in their code, they can access all the functions of the library
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9
Q

How do libraries save developers time?

A
  • Common tasks can be written as libraries for repeated use
  • This saves time for developers as it saves them from having to rewrite the instructions
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10
Q

What are translators?

A

Translators are systems software tools that are used to convert program code from one format into another, without adjusting the logical operation of the original program code

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11
Q

Name three types of translator

A

Compilers, Assemblers, Interpreters

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12
Q

What is the purpose of compilers?

A

To turn program source code into a target language version (eg machine code / bytecode) that can be executed by the computer

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13
Q

What is the purpose of assemblers?

A
  • To turn low-level assembly language code into executable machine code
  • They are very fast to run
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14
Q

How do interpreters work?

A

Interpreters run instructions from a high-level language by determining what actions should occur line-by-line and executing equivalent prewritten executable code.

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15
Q

Why is the operating system classified as systems software?

A

It is required for the functioning/maintenance of the system itself, and performs tasks that are machine oriented

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16
Q

2 main roles of OS

A
  1. To hide the complexities of the hardware from the user
  2. To manage the resources which processes compete for

Give a concrete example, e.g. “To allocate I/O devices to processes”

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17
Q

How does the OS hide the complexities of the hardware from the user?

A

By presenting the user with a virtual machine to interact with.
e.g.
- 🖼️Graphical User Interfaces (GUIs)
- 👨‍💻Command Line Interfaces (CLIs)
- Application Programing Interfaces (APIs)

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18
Q

What is a virtual machine?

A

A virtual machine is the apparent machine or interface that the OS presents to the user

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19
Q

What is an API (in the context of the operating system)?

A
  • An application programming interface
  • APIs are layers of software that allow the application programmers use the functions the OS provides
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20
Q

What is a process?

A

A process is an instance of a program being executed

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21
Q

4 resources processes compete for

A
  • (Secondary) Storage
  • I/O Devices
  • Memory
  • Processor time
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22
Q

4 ways OS manages storage

A
  • Allocating space on storage devices to files
  • Organising files into directories
  • Determining where on the device to save a file
  • Manages which process/user can access (read/write/modify) different files and directories
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23
Q

How does OS manage I/O devices?

A
  • By allocating I/O devices to different processes
  • And managing communication between the processes and devices
24
Q

How does OS manage memory?

A

By allocating different parts of main memory for all the processes. (Locations may not be contiguous)

25
Q

How does OS manage processors?

A

By allocating processor time to each of the processes (aka processor scheduling)

26
Q

4 characteristics of a low-level language

A
  • They are defined by the processor they are designed to run on
  • Non portable - they are specific to the instruction set of the processor they are written for
  • They are machine-oriented and have no built-in functions
  • There is a one-to-one mapping between a low-level language instruction and its equivalent machine code language instruction
27
Q

Why are low-level languages non-portable?

A

They are specific to the instruction set of the processor they are written for

28
Q

What two things make up a low level instruction?

A
  • Opcode - an mnemonic which represents the machine operation that the processor should perform
  • Operand(s) - a value or set of values relevant to the opcode
29
Q

3 things the operand of a low level instruction can be, and what addressing type it is

A
  • memory locations (direct memory addressing)
  • register values (direct register addressing)
  • actual decimal values (the operand is the datum) (immediate addressing)
30
Q

Why is hexadecimal used in some low level languages?

A
  • Binary machine code is difficult for humans to debug and fix problems in.
  • So hexadecimal is usually used instead, as it is easier to read and understand
31
Q

What is assembly code? (2*)

A
  • A low-level language that uses a set of mnemonics that represent binary machine code instructions
  • Assembly code is converted into machine code using an assembler.
32
Q

3 characteristics of high-level languages

A
  • High-level languages are problem oriented
  • Portable - not specific to any type of processor
  • One instruction in a high-level language represents many instructions in a low level language
33
Q

What is an imperative language? (2*)

A
  • A high level language where a problem is solved by writing a sequence of instructions that state how it should be solved
  • It has structures for assignment/iteration/selection and uses English-like keywords for these
34
Q

4 pros of high-level languages

A
  1. Programs are machine independent / portable
  2. People find it easier to debug high-level language programs
  3. People find it easier to read/write/understand high-level language program code
  4. Saves time for programmers as they use fewer lines of program code
35
Q

4 cons of high-level languages

A
  1. Programs written in a high-level language may not make best use of specific features of a particular processor
  2. Programs written in a high-level language may not execute as quickly
  3. Programs written in a high-level language may use more memory
  4. Some programs are easier to write using a low-level language - e.g. some parts of a computer’s operating system
36
Q

4 pros of low-level languages

A
  1. Programs written in a high-level language may not make best use of specific features of a particular processor
  2. Programs written in a low-level language may execute quicker
  3. Programs written in a low-level language may use less memory
  4. Some programs are easier to write using a low-level language - e.g. some parts of a computer’s operating system
37
Q

4 cons of low-level languages

A
  1. Non-portable as they are specific to the instruction set of the processor they are written for
  2. People find it harder to debug low-level language programs
  3. People find it harder to read/write/understand low-level language program code
  4. Requires programmers to write more lines of program code
38
Q

How are logic gates used in a half-adder?

A

XOR for S(um)
AND for C(arry)

39
Q

What are S, C_in and C_out in a full adder?

A
  • S is the sum
  • C_in is the carry from the previous calculation
  • C_out is the carry that is going to be passed to the next calculation
40
Q

Inputs for an edge-triggered D-type Flip-flop

A

D and a clock signal

41
Q

Outputs for Edge-triggered D-type Flip-flop

A

Q and not Q

42
Q

What is the purpose of the clock in an Edge-triggered D-type Flip-flop? (2*)

A
  • To synchronise the change of state of the circuit
  • The clock oscillates between low and high signals at regular time intervals
43
Q

How does Q change in an Edge-triggered D-type Flip-flop?

A
  • On the rising edge of the clock signal, Q and not Q are updated to hold D and not D respectively
  • Output Q only takes on a new value if the value at D has changed at the point of a clock pulse
44
Q

How can an Edge-triggered D-type Flip-flop be used?

A

As a memory unit

45
Q

What is a low-level language?

A
  • A language that is based upon the instruction set of a processor
  • They are defined by the processor they are designed to run on
46
Q

What is immediate addressing?

A
  • When the operand value is an actual decimal value that is part of the instruction
  • There is no need to go to any memory address in this case
47
Q

3 advantages of compilers (over interpreters)

A
  • The source code cannot be accessed by users
  • Users do not need to have an interpreter to the run the program
  • The program will execute more quickly
48
Q

Why is code that will be executed in a web browser often interpreted rather than compiled?

A
  • It’s impossible to know what type of processor will be in the user’s computer
  • A compiled program will only execute on a processor of a specific instruction set, whereas interpreters can execute on a computer with any type of processor
49
Q

Why are translators necessary? (2*)

A
  • High-level instructions cannot be executed directly
  • Processors can only execute machine code instructions
50
Q

How do compilers and interpreters approach errors differently?

A
  • Compilers analyse the program as a whole, and will not translate any of the program if it encounters an error
  • Interpreters analyse the program on a line-by-line basis, and execute until the first error is encountered
51
Q

Give an example of an intermediate language and how it’s used

A
  • Bytecode
  • Compilers convert high-level code into bytecode, and then use a virtual machine to execute the bytecode on different processors
52
Q

What is the difference between source code and object code?

A
  • Source code is the input to a translator
  • Object code is the output of a translator
53
Q

Explain the relationship between hardware and software

A
  • Software is the programs that execute on the hardware
  • Hardware is the physical components that allow the software to execute
54
Q

What is the name of the sequential circuit with a Data and Clock input that can be used as a memory unit?

A

Edge-triggered D-type flip-flop

55
Q

Simplify A . (A+B)

A

A
(can be a useful shortcut)

Computer Science (11 decks)

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