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Computing p > 3.4a Computer Systems > Flashcards

3.4a Computer Systems Flashcards

1
Q

Hardware - define + 5 examples

A

Hardware is the physical components of the computer, such as the central processing unit (CPU), hard disk, monitor, keyboard and mouse.

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2
Q

Software - define

A

Software is the programs that run on a computer.

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3
Q

Aside from the internal components of a computer, what allows the user to communicate with the system ?

A

Additional hardware- through inputs + outputs

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4
Q

4 input devices

A

Mouse, keyboard, camera, microphone

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5
Q

4 output devices

A

Screen, speakers, printer, LEDs

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6
Q

Software function?

A

The software in a computer system enables the hardware to function and the user to perform tasks.

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7
Q

2 main types of software within a computer system

A

Software within a computer system is divided into two main types, system software and application software.

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8
Q

System software definition + 3 examples

A

System software is any software that assists with the running or management of the computer system.

This can include operating systems, security software and file management software.

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9
Q

Application software definition

+ 2 examples (with functions)

A

Application software is any software added to the system that enables the user to perform a task.

For example, a word processor allows the user to type a document and a browser allows the user to view web pages.

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10
Q

Define operating system

A

An operating system is a collection (or suite) of programs that manages and controls the computer.

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11
Q

Functions of operating systems (8) — bitsize

A
  • controlling hardware components
  • providing a platform for software to run on
  • providing a user interface
  • managing processes
  • managing the computer’s memory
  • managing input and output devices
  • managing applications
  • managing security
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12
Q

Fucntions of an operating system - Uncle Fred …

A
  • user interface
  • file management
  • user management
  • peripheral management
  • memory management
  • multitasking
  • device drivers
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13
Q

5 operating system examples

A 
Microsoft Windows
Apple OS X
Linux
Android
IOS
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14
Q

What is a user interface>

A

A user interface is a program, or suite of programs that allows a user to interact with a computer.

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15
Q

3 types of interface? - one of them is also known as

A

There are three types of interface to be considered:

  • graphical user interface (GUI) - sometimes known as WIMP (Windows, Icons, Menus, Pointers) interface
    mobile user interface
  • (Mobile UI)
  • command line interface (CLI)
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16
Q

Graphical User interface

  • what
  • how
  • access
  • interaction
A

A graphical user interface is familiar to most users of PCs and laptops.
GUIs feature a desktop where everything is displayed.
Applications run in Windows, and all objects (apps, hardware and files) are represented by icons.
Application features are accessible through the use of menus.
Users interact with the interface by using a mouse and on-screen pointer.

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17
Q

GUI adv + disadv

A

GUIs are powerful and easy to use, but require a lot of processing power.

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18
Q

Mobile UI?

  • what
  • how
  • where found
A

Mobile UIs are similar in many ways to GUIs, except that they respond to touch. Fingers are used to open programs and interact with them. Gestures such as swiping are used to scroll within documents. Pinching and stretching are used to re-size images.

Mobile UIs are found on smartphones and tablets.

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19
Q

Command line interfaces

  • what
  • how
  • when
A

Command line interfaces are text-based.
Users control the computer by typing in commands.
Originally most interfaces were CLIs, and they still exist within modern operating systems, for example the command prompt app in Windows, and Terminal in OS X.

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20
Q

Command line interfaces adv (2) + dis (1)

A

CLIs require little processing power and are extremely powerful, but are difficult to use.

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21
Q

Processors management relates to what?

A

Multitasking

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22
Q
  • Define multitasking
  • these programs perform __
  • multitasking in the past?
A

Multitasking means to be able to run more than one program simultaneously. These programs perform processes.

In the past, computers with CLIs were unable to multitask - the operating systems of the day only allowed one program to run at a time.

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23
Q

Things you can do multitasking (3/4)

A

Modern operating systems are multitasking in that they allow several programs to run side-by-side.

It is not uncommon for a user to be streaming music while entering text into a word processor, or streaming a video while making a backup of files.

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24
Q

Multitasking is possible only if: (2)

A
  • the operating system can support multitasking

- the computer has enough memory to hold more than one program in primary memory at the same time

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25
Q

Memory management:

Computer memory must be managed to ensure that: (2)

A
  • more than one program can run at the same time

- more than one document can be opened at the same time

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26
Q

Describe one method of memory management

A

One method of memory management is known as paging.
Memory is broken up into fixed-size blocks, known as pages.

Paging is a method of managing memory. It divides memory up into small blocks known as pages and allocates enough pages to hold a program.

27
Q

What size do operating systems allocate to pages?

A

Different operating systems allocate their own size to pages. For example, memory pages in modern operating systems are typically 4 kilobytes (KB) in size.

28
Q

Tell me how memory works, when a program is run - paging (3)

A
  • When a program is run, it is loaded into memory.
  • The operating system determines how much memory the program requires, and allocates enough pages to hold it and its documents.
  • When the program is closed, the allocated pages are freed up for use by other programs.
29
Q

Contiguous meaning

A

Running together in sequence, one after another.

30
Q

Are the pages a program occupies contagious ?

- why does/doesnt this matter?

A

The pages a program occupies may or may not be contiguous, but this does not matter.
The operating system knows what each page occupies and fetches the data held in them when needed.

31
Q

So practically do you know how paging works?

A

Quite easy.

https://www.bbc.co.uk/bitesize/guides/z7qqmsg/revision/2

32
Q

Input/output devices management:

  • Input and output decides are also know as __?
  • What are they?
  • 4 examples
A

Input and output devices, which are also known as peripherals, are hardware devices connected to a computer, such as a screen, printer, keyboard or camera.

33
Q

How do operating systems operate a peripheral ?

A

To operate a peripheral, the operating system uses a program called a device driver. Device drivers contain instructions on how to control a device. Each connected device has its own driver.

34
Q

Using device drivers brings two advantages:

A
  • any device can be used with the operating system, as long as a driver is available for it
  • drivers can be updated, usually to give better performance or to remove a bug
35
Q

Operating systems use device drivers to control what?

A

peripherals

36
Q

Application management:

How can application programs and hardware are communicate ? (2)

A

Application programs and hardware can communicate through an interface provided by the operating system.
This is known as the application programs interface (API).

37
Q

What does the applications manager do?

A

The applications manager allocates memory space and determines time needed by a processor for an application to run.

38
Q

Security management:

Operating systems also manage security. They allow: (3)

A
  • individual users to be created and deleted
  • access levels to be given to users, such as administrator rights or standard user rights
  • auditing (keeping a log) of files a user creates, accesses, edits and deletes
39
Q

Utility software purpose

A

Utility software helps maintain the system

40
Q

Utility software includes: (4)

A
  • encryption software
  • defragmentation software
  • data compression software
  • backup software
41
Q

What is encryption ?

What does it require?

A

Encryption is the process of disguising a message so that it cannot be understood by anyone but its intended recipient.

Encryption requires the use of a key. The key is secret as to how the message has been disguised

42
Q

Unencrypted messages =

Encrypted messages =

A

Unencrypted messages are referred to as plaintext messages and encrypted messages are known as ciphertext.

43
Q

Describe a simple method of encryption

A

A simple method of encryption requires the use of a technique known as the Caesar cipher. The cipher works by giving a number value to a key. Each plaintext letter is replaced by a new letter, the one found at the original letter’s position in the alphabet plus the value of the key.

For example, a key value of 3 would change the plaintext message “see you tonight” to the ciphertext message “vhh brx wrqljkw”.

A table containing plaintext and an example ciphertext
To decrypt the message, the process is reversed.

Although this is a good example of encryption, much more complicated algorithms are used to encrypt messages today.

44
Q

Encryption - how - don’t necessarily need to know - on spec? - dont think so - answer taken from ocr

A

use an algorithm that generates two keys - a public key and a private key. This method is known as asymetric encryption. A public key can be given to anyone. Anyone can then use this key to encrypt a message. However, the public key cannot decrypt a message - only the second key (the private key) can do that. So long as the private key is never given out, messages will stay safely encrypted.

Online banking makes use of public and private keys. When a user logs on to their bank, they do so using a public key supplied by the bank. All communication with the bank is encrypted, and only the bank can decrypt the messages using the private key.

45
Q

Encryption in use (3) - ocr

A

Today, most communications sent via the internet are encrypted in some way:

  • purchases made online are encrypted to try to prevent theft of credit card details
  • tools enable a user to encrypt a document, such as a spreadsheet, before sending it to a colleague via the internet
  • satellite TV transmissions are encrypted to prevent users who are not subscribed from watching TV shows
46
Q

What can software encrypt (2) - last wierd question dw

A

The software can encrypt specified files, or the whole of the hard disk on which the files are stored.

47
Q

What’s fragmentation - whys it a problem

A

When a file is stored on a hard disk it is actually stored not as a whole file, but as a series of segments. Sometimes the segments run together in sequence (see File 1) and sometimes the segments are split up over a disk (see File 3). This is known as fragmentation.

Over time, more and more files become fragmented, as do individual files. A fragmented disk takes longer to read from and write to, making a computer run slower.

Diagram:
https://www.bbc.co.uk/bitesize/guides/z7qqmsg/revision/3

48
Q

What defragmentation is?

- good because?

A

Defragmentation software takes the fragmented files and rearranges the segments so that they run contiguously. This decreases read/write time, thereby speeding up computer performance.

From mock:
• Files on the hard disc drive are moved (1)
• Empty spaces collected together (1)
• Files are moved to be stored together (1)
• Fewer disc accesses are needed (1)

49
Q

BAckup software:

How can data be lost (3)

A

Data can be lost accidentally, or deliberately.

  • A user may accidentally delete or overwrite a file,
  • or a hard disk may fail, preventing access to any files stored on it.
  • A hacker or malicious user may deliberately delete or overwrite data.
50
Q

How to prevent data loss?
What is a backup - meaning?
What should backups contain?

(3)

A

To prevent data loss, regular copies of the data should be made.
A copy of data is known as a backup.
Backups can contain a copy of all files on a computer, or just ones specified by a user.

51
Q

How do backups actually work then

  • how
  • when
  • where
A

Network managers make regular backups of all files on a network using backup software.
The software automatically makes a backup at a scheduled time of day, usually during the evening when the network is quiet.
Backups are usually made to a high capacity secondary storage device, or to the cloud.

52
Q

If data loss occurs, why is backup useful?

What does backup software allow retrieval of (2)?

A

If data loss occurs, data can be retrieved from the backup. The software allows all backed-up files to be retrieved or just specified files.

53
Q

2 types of backup

A
  • full backup

- incremental backup

54
Q

Full backup

  • what?
  • disadvantage?
A

A full backup involves making a copy of every file on the computer or network. They can require a lot of storage space and can be time consuming to make.

55
Q

Incremental backup

  • what?
A

Incremental backups take a copy of any new files created since the last backup, or of any files that have been edited, such as user documents.

56
Q

So when full/incremental backups used?

And why?

A

Most network managers make an initial full backup and then switch to daily incremental backups. This way all data is backed up and daily backups are small and less time-consuming.

57
Q
  • some of 3.4.5 systems architecture has been removed -
A

Advanced information

58
Q

What are registers?

A

Registers are small amounts of high-speed memory contained within the CPU.

59
Q

NEEDED - What are registers used by?
And to?

+ 3 examples

A

They are used by the processor to store small amounts of data that are needed during processing, such as:

  • the address of the next instruction to be executed
  • the current instruction being decoded
  • the results of calculations
60
Q

Different processors have different numbers of registers for different purposes, but most have some, or all, of the following:
(5)

A
  • program counter
  • memory address register (MAR)
  • memory data register (MDR)
  • current instruction register (CIR)
  • accumulator (ACC)
61
Q

NEEDED - What is cache?

A

Cache is a small amount of high-speed random access memory (RAM) built directly within the processor.

62
Q

What is cache used for?

+ adv, w/ explanation

A

It is used to temporarily hold data and instructions that the processor is likely to reuse.
This allows for faster processing as the processor does not have to wait for the data and instructions to be fetched from the RAM.

63
Q

A processor based on Von Neumann architecture has five special registers which it uses for processing:

  • what are they - and what do each of them do?
A

Program counter (PC) - holds the memory address of the next instruction to be fetched from main memory.

Memory address register (MAR) - holds the address of the current instruction that is to be fetched from memory, or the address in memory to which data is to be transferred.

Memory buffer register (MBR) - holds the contents found at the address held in the MAR, or data which is to be transferred to main memory. It is also referred to as the memory data register (MDR).

Current instruction register (CIR) - holds the instruction that is currently being decoded and executed.

Accumulator (ACC) - holds the data being processed and the results of processing.

64
Q

The fetch-execute cycle (also known as fetch-decode-execute cycle) is followed by a processor to process an instruction. The cycle consists of several stages. (7)

  • removed from our exams - but just for information
A

1- The memory address held in the program counter is copied into the MAR.
2- The address in the program counter is then incremented - increased - by one. The program counter now holds the address of the next instruction to be fetched.
3- The processor sends a signal along the address bus to the memory address held in the MAR.
4- The instruction/data held in that memory address is sent along the data bus to the MBR/MDR.
5- The instruction/data held in the MBR/MDR is copied into the CIR.
The instruction/data held 6- in the CIR is decoded and then executed. Results of processing are stored in the ACC.
7- The cycle then returns to step one.

Computing p (23 decks)

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