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Flashcards in Computers Deck (119):

whatare the components of the CPU

- control unit
- decoder
- clock
- arithmetic logic unit
- buses
- cache
- registers


what is the function of the control unit

- controls all other components in CPU
- Contains the decoder


what is the function of the decoder

- interprets program instructions
-tells the ALU what operations to do


what is the function of the clock

-Controls rate which program instructions are carried out
-Sends control electrical signals in cycles


what is the function of the arithmetic logic operator

-Arithmetic and logical operations done to carry out program instructions


what is the function of the buses

-Electrical conductors that carry electrical signals in the CPU and btwn the CPU and other components on the motherboard


what is the function of the registers

- memory locations.
- some perform special functions in the fetch-decode-execute cycle


what is the function of the cache

- very fest random access memory (RAM)


what factors affects the performance of the CPU

- clock speed
- cache size
- number of cores
- type of RAM
- hard drive speed


what does it mean if a processor is quadcore

it can carry out 4 instructions at the same time


what is clock speed

- the amount of clock cycles that take place within one second
- measured in gigahertz (GHz)
- CPU carries out one instruction per clock cycle


what is the purpose of the CPU

- To fetch and execute program instructions stored in memory.

- often referred to as Von Neumann architecture


name all four different types of registers in the CPU

- program counter
- MDR (memory data register)
- accumulator
- MAR (memory access register)


what is the function of the program counter (register)

- holds the address of the next instruction to be fetched.
- uses the fetch-decode-execute cycle


what is the function of the MDR (memory data register)

- temporary store for anything copied from memory


what is the function of the accumulator (register)

- stores the results of calculations carried out by the ALU


what is the function of the MAR (memory access register)

- holds the address of the memory location currently being read/fetched or written to
- uses the fetch-decode-execute cycle


why is the performance of the CPU affected by the number of cores you have

- more cores = more instructions can be carried out per second therefore the computer will be quicker


explain why a computer with a 2.2GHz CPU might be considered preferable to one with a 1GHz CPU

- the clock sends out electrical control signals at regular intervals.

- the rate of the pulses affect the execution of instructions by the CPU

- the 2.2 GHz CPU can carry out 2.2 billion processing cycles per second so is faster than the 1 GHz CPU that can carry out 1 billion processing cycles per second


identify 3 components of a CPU and state their role within the fetch-decode-execute cycle

- the CU controls all the other components of the CPU and decodes all insturtions

- the buses carry electrical signals & data to be stored btwn CPU and RAM

- ALU performs arithmetic and logical operations to carry out program instructions


what is the fetch - decode - execute cycle?
how many cycles does it take?

- The CPU uses the fetch - decode - execute cycle to carry out the program instructions

- this cycle takes 3 clock cycles



used to retrieve the location of the data where the CPU must read/ write to


Operating systems control the ways in which users interact with the computer through the user interface and control peripheral devices (able to be attached to and used with a computer, though not an integral part of it.)

User interface

Allows the user to communicate with the computer

Many OS provide a GRAPHICAL USER INTERFACES (GUI) with Windows, Icons, drop down Menus and Pointers (WIMP)

Common GUIs are Windows, iOS and Android

Other interfaces just allows the user to type in commands


User management

On networks and shred computers the OS MANAGES USERS. Login manes/passwords are used to allocate permissions for access to files and folders

Often used in organisations to prevent individual users making changes to computer software/ making inappropriate usage of the computer

Peripheral device management

Most computer systems use peripheral devices for input & output of data

Input devices:






Output devices:



External/internal monitor


External hard drives and network storage devices are also peripherals. Al peripherals are controlled by the OS using programs called DRIVERS

The drivers carry out the necessary devices to communicate correctly



Utility software is a collection of tools, each of which does a specific job. It helps to configure the systems, analyse how it working and optimise it to improve its efficiency

Encryption software

Encryption is the scrambling of data into a form that cannot be understood by unauthorised users. It's used to protect data from unauthorised users of the computer. The encrypted data must be decrypted data back to its original form. Encryption/ decryption is carried out using a CIPHER or key

Defragmentation software

Data is saved to different areas of the discs where there is free space.

If the file is larger than the free space in one part of the disc, then part of the file is saved in that space and some more in another area. This is known as fragmentation

Overtime, this reduces efficiency as more disc accesses are needed to read the complete file.

Defragmentation software reorganises the files by putting pieces of related data back together, fewer disc accesses are needed to read the data.

This improves performances and can free up more space on the hard disc

Data compression software

Uses algorithms to REDUCE the size of files meaning less storage space is required & transmitting files by email/uploading or downloading using cloud services is easier

Commonly used for audio/ video files

LOSSLESS COMPRESSION reduces the size without deleting any of the data, important for text files

LOSSY COMPRESSION reduces the size by deleting some of the data


Involves copying files to a second medium i.e. a disc/tape/cloud service so they can be restored if there's any problems with the originals

Can compress the data to take up less storage space

With a full backup, all of the specified data is backed up

With an INCREMENTAL backup only new files/ edited files with new changes applied since the last backup are saved to save time

Some backup software will copy files continuously so long as the computer is switched on. Other software will only run at specific times

State what is meant by backing up a computer

It involves the copying of data stored on a computer system onto a separate storage device ie a disc or tape

Describe the difference between a full backup and an incremental backup

In a full backup, all of the data on the computer is coped

In an incremental backup, only the data that is new/ has been changed is copied



Computer modelling

A computer model attempts to abstract the rules and mechanisms that control real-life systems and apply the, in computer programs so that they can be used to stimulate the behaviour of those systems under different conditions. The models can be used to answer 'what if' questions eg what will happen if this condition is met. The simulations will only be successful if all the rules abstracted from the real-life systems are correct

Examples of simulations

FLIGHT simulations (allows pilots to train to fly passenger aircraft without the actual cost of using actual aeroplanes)

TRAFFIC FLOW simulations (models are used to simulate traffic when new roads and motorways are being planned)

WEATHER FORECASTING simulations (models are used to simulate the atmosphere and changes that affect the weather)

FINANCIAL MODDELLING (used to investigate the effect of changing tax rates when budget changes are being investigated)

Advantages of using computer models

Safety (ability to experiment without harming people or the environment)

Financial (new products can be tested without having to build prototypes ie cars/aeroplanes)

Repetition (tests can be quickly repeated to ensure similar outcomes)

Adjustments (changes to the rules and input data can be made quickly to see the outcomes)

disadvantages of using computer models

The mathematical calculations may be too complex to model real life situations

May be difficult to identify all of the rules correctly

The model is not reality so the answers may not be correct

The processing power needed to run the model may be greater than what is available

Modelling software

Specialist software can be purchased for creating specific types of model ie finance, electronics chemical reactions and biological processes

Spreadsheets can be used to model most situations as rules and formulae can be applied to specific cells and models can be created in most programming languages

Can be used to investugate effects of increasing global temperate of sea levels on the world



Instructions for computer are written in programming languages that need to be translated into machine code before the computer can understand then

Low levels languages

Machine language (processors only understand instructions written in 1s and 0s. At the processing level computer programs are in the form of millions and 1s and 0s, known as machine code/ languages)

Assembly language (assembly language when each instruction is directly equivalent to one in machine code. Words called mnemonics are used to replace the command represented as strings of 1s and 0s in machine code ie ADD is a mnemonic used to replace the binary command to add numbers together)

Uses of low level languages

Assembly language is often used in the programs used by embedded systems ie in in cameras, microwaves and TVs as it can be used to directly control system hardware

They're used to write device drivers and real-time systems where speed is essential

Assembly language is specific to each type of CPU. Program written for one type cannot be used on others

Uses of high level languages

Most software is developed using a high level language. Its less time consuming to write and quicker to test

Programs are portable from one machine to another

Most high level languages can be used with different types of CPU

High level languages:

Three reasons to use a high level languages for software development:



compare the performance of:
specification 1 (3GHz, 64bit CPU, 4MB cache, 4GB RAM)
specification 2 (4GHz, 64bit CPU, 4MB cache, 8GB RAM)

- spec 2 would be quicker in terms of the clock speed. bc it has a higher clock cycle speed (4GHz) meaning that the clock will send more electrical impulses to the CPU and more instructions per second will be completed. However, specification 2 may be quicker because there is double the RAM available. This would mean that there would be double the instructions/ amount of data to be stored whilst the computer is running. Overall, I believe that the specification 2 will be quicker overall because the clock speed is 25% faster meaning there will be a quarter of the instructions/ processes completed whilst the computer is on


what is open source software

-Free software that users can download.
-Source code is available to users


what is the difference btwn pop and imap protocol

POP = Emails downloaded on to device
IMAP = Emails stored on a server


what are protocols

-Ensures data is sent in a format that all computers can read
-Has address formats to ensure data is sent to the correct computers
-Chooses the route of the data


what are the TCP/IP layers for sending data



what is TCP/IP

- Transmission Control Protocol/Internet Protocol
-splits data to packets and reassembles
-Address needed
Notifies sending computer that info has been recieved


what is FTP protocol

-File Transfer Protocol
-Rules for file transfer
-Used to transfer files too large to beattached to an email


What is SMTP

-Simple Mail Transfer Protocol
-Rules for sending Emails
-Goes from client to different servers until it reaches its destinantion


What is IMAP

-Internet Message Access Protocol
-Emails stored on server
-Can be read from any device


What is HTTP protocol?

-Hyper Text Transfer Protocol
-Rules for web browser and server when requesting and supplying information


What does the application layer do?

- provides services to applications ie web browsers/email servers
- where requests are made and emails sent
-HTTP(S) and POP


What does the transport layer do?

-Puts data in packets
-Checks data has been sent/received
-Notifies sender that data has been recieved
-TCP and UDP


What are switches?

-Reads MAC address
-Sends only to recipient
-Big and expensive


What is an NIC?

-Network Interface Controller
-Used to connect to a network
-Is in chip on a motherboard of a computer
-Formats data sent and received


What is a MAC address?

-NIC's Media Address Control (MAC)
-Ensures data directed to correct computer


What is an internet layer protocol example?



What are link layer protocol examples?

Ethernet/Wifi Protocols


What's a router?

-Connects networks
-Reads address info
-Transfers data between home network and internet


What are wireless access points?

-Convert data through cables into a wireless signal
-Doesn't read destination addresses
-Info sent to everyone
-used for hotspot


Cable networks pros and cons (One computer)

-High bandwidth
-More secure (Just needs a plug)
-No interference
>Installation difficult
>Poor mobility


Pros/Cons Open source software

-Free to use
-Users can change software
-Source code can be studied
>Needs specialist knowledge


What's POP protocol?

-Post Office Protocol
-Mail downloaded from server when there is a connection


What is a HUB?

-Doesn't check address(Sends info to everyone)
-Causes unnecessary network traffic
-Cheap and small


Wireless Pros and cons

-Easy to install
>lower bandwidth
>Needs security passwords
>Signals can be interfered by walls


Why is Fibreoptic better than copper?

Faster and travels over longer distances


What sort of waves does wireless use?

Radio waves


what are high level programming languages

- similar to natural human language
- it uses key words ie 'print', 'if', and 'then'.
- Programs written in high-level language have to be translated into machine code to operate


what type of memory stores a computers start up programs



what software is used to imitate a real life situation

simulation software


what component of the CPU holds the current program instruction



describe the concept of a stored program

when a computer stores program insturctions in its electronic memory


what are the 3 functions of an operating system

- manages the memory (many programs request data to be loaded)
- allocates CPU time to different applications (the require the CPU to execute program instructions)
- provides the interface btwn a user and computer system


what is the organisation you must pay to access the internet

internet service provider


describe the topology of a star network

- all nodes are individually connected to a central connection point, like a hub or a switch
- they are not connected to each other


describe the role of a wireless access point on a network

- they convert data received through cables into wireless signals and vice versa
- directs messages to all devices


describe the role of a router on a network

- it transfers data btwn the internet and a home network
- reads address info & forward messages to the correct network


explain the effects of using the JPEG compression format for images

- it's an example of lossy compression so this deletes data
- it has been irreversibly changed as the data cannot be restored


24 bit images must be displayed on a screen at a resolution of 400 x 250 pixels

contruct an expression to calculate the size of one of the image files (KB)

(24 x 400 x 250) / (8 x 1024)


24 bit images must be displayed on a screen at a resolution of 400 x 250 pixels

convert BB4A0F into binary



why is hexadecimal easier than binary when specifying screen colours

- its easier to remember and easier to enter 6 digits than 24 digits so less human error and less storage space


identify a binary system used to represent text



explain the concept of overflow in relation to binary notation

- when a calculation is performed by the computer & the result is greater than the computer can handle/represent (more than 8 bits)


describe the result of carrying out an arithmetic shift right one place to an 8 bit binary integer



explain why run-length encoding algorithm may not be appropriate for encoding this image



desbribe the difference btwn structured and unstructured data

> Structured data is data arranged in an organised, defined way and is easier for a computer to process because data is arranged in a standard, precise layout.
> Easy to work with

> Unstructured data has no set way for a computer to interact with it and cannot be easily mapped by a computer into pre-defined fields.
> not that easy to work with.

> An epitome of structured data is the database.


define Malware

– software that has been designed to gain unauthorised access to a computer system in order to disrupt its functioning/ to collect information


define Spyware

- software that spies on users by sending screenshots/ key presses to the hackers computer, revealing passwords

– often comes packaged with other software ie free software, the user not knowing they're installing it.


define Virus

– computer program hidden in another program, usually having a harmful effect ie corrupting/ deleting data on a disc.
- Can replicate & insert itself into other programs/ files which can be passed on


what are High level languages

Programming languages that resemble human languages.
They use key words such as print, if and then.
- they address the programming logic rather than dealing with hardware issue such as memory addressing.
- Most programs are written in high level languages


what does Antivirus software do

– checks all files that're loaded onto a computer for viruses. Can be set to carry out routine scans & viruses in emails


what does Antispyware software do

– checks for and blocks spyware


how do antimalware check for malware

- They scan for malware using a database of known malware definitions (signatures), constantly being updated

- Some use a form of analysis called HEURISTICS
these use a set of rules to detect malicious behaviour by analysing the programs/files behaviour.


what does File conversion software do

– converts one type of file format to another so it can be used by another program ie text/ spreadsheet/ database files.

- useful for media files ie images/videos where there're different file formats (AVI/MP4/FLV)


what does File repair software do

– type of data recovery software that can repair corrupted files, that could've been corrupted by malware or a computer malfunction


what happens in the fetch cycle of the fetch-decode-execute cycle

- the CU sends a 'read' signal to the RAM on the control bus.
- the CU uses the address bus to send signals specifying the required memory location in the RAM.
- this data is transferred to the CPU along the data bus


what happens in the decode and execute cycles of the fetch-decode-execute cycle

instructions and interpreted and carried out:

- program instructions/ data is sent to the CU from the RAM
- the CU decodes the instruction then executes it. if a calculation needs to be performed it instructs the ALU
- calculations are carried out by the ALU


state what is done briefly at each stage of the fetch-decode-execute cycle

- fetch: the next institution to be executed is transferred from the RAM to the CPU
- decode: the CU interprets the institution
- execute: the CU then carries out the instruction and instructs the ALU if calculations need to be performed


define secondary storage and give examples of secondary storage devices

- any non volatile storage device that is internal or external to the computer
- ie USB flash drives or floppy disks


how is data stored on Magnetic storage devices
give an example

- Data is encoded as opposing magnetic polarities on the surface of the disc by electromagnets in the read/write heads
- The disc spin & reads/writes heads move across the discs

- ie hard disc drives which consist of stacks of non-removable discs coated with magnetic materials


why are secondary storage devices needed

- unlike RAM that is volatile, secondary storage doesnt lose its data when there's no power
-meaning it provides permanent storage for programs/data that would otherwise be lost when the computer is stitched off
- Ie USB flash drive


name all three types of storage device

magnetic discs
optical disks
solid state (flash) memory



how is data from secondary storage devices processed

- data is stored permanently on secondary storage devices but the CPU cannot access them directly
- they are therefore transferred to the main memory


how is data stored on Optical storage devices

- Digital data is stored along the track by etching PITS onto the surface of the disc
- When the light from a laser hits the LANDS it is reflected back to a detector but is scattered away by the pit & no light is detected. The two events are represented by '1' and '0'


how is data written to a recordable CD-R (optical storage)

- the discs surface covered by a translucent dye so light passes through
- data is written to the disc by a powerful laser burning the dye creating black spots that dont reflect light
- the reflecting areas are interpreted as 1s and black spots as 0s


what is cloud storage

OFFSITE storage (not on a company's premises – elsewhere in the world) made available to users over a NETWORK, usually the internet


compare backing up data to a magnetic hard disc with an optical disc

- hard disc drives magnetically store data by electromagnets in read-write heads encoding data as opposing magnetic polarities on the surface of the discs

- when data is written to a CD-R a powerful laser light burn the light on the surfaces creating black spots that dont reflect laser light. the area that reflect and do not reflect are interpreted as the digits 1s and 0s


how does multitasking work on a computer with a single core processor

- multitasking is the process where programs appear to run concurrently
- but in fact the OS is sharing out CPU time btwn each task so in turn they can be processed
- the CPU switches between the tasks and priorities them so some have more CPU time than others


how is memory managed in a computer

- the OS prioritises tasks and allocates time slot to each process
- checks all requests for memory are valid and allocates it accordingly
- swaps out data to the virtual memory when the main memory is full


list the advantages of using a flash memory device rather than a magnetic disc drive for data storage

- faster access
- quiter
- lighter & more portable
- solid state (more portable)
- less easily damaged
- less likely to lose data


state the disadvantages of using flash memory

- more expensive than magnetic storage (price per GB)
- maximum storage capacity available is lower than by modern magnetic disc drives
- has a shorter life span than hard disc drives


explain how each secondary storage device physically records data:
magnetic hard drive
flash memory USB stick
optical disc drive

- hard disc drives use electromagnetism to store data magnetically on metal discs
- flash memory USB sticks use electricity to change the state
- DVDs use light produced by a laser to store data on the disc by changing its surface


what are the uses of flash memory (give examples)

- solid-state drives (SSDs) provide secondary storage instead of magnetic storage
- secure digital (SD) cards are used in portable devices ie phones and cameras
- USB flash drives are convenient compact forms of flash memory for sharing & transferring data


what is the function of systems software

Utility software on a computer is a set of tools that can be used to analyse and optimise efficiency



Application software

It is an end user program

Also called applications, and user programs perform user-identified tasks such as word processing & photo editing or are used for entertainment such as games viewing videos

Memory management

In a computer system many programs will be running at the same time, called multitasking

Although programs appear the run at the same time the OS is sharing out processor time between them so that into turn they can have their program instruction processed

These activities that're being performed are called processes

Some processes are visible to the user as application software but many aren't seen by the user

There are usually programs & processes that the user cannot see running in the background

All processes require the use of the CPU and memory

The OS prioritises the tasks & allocates time to each process

It checks that all requests for memory and valid& allocates it accordingly

It then swaps out data to the virtual memory when the main memory is full

File management

The OS creates a folder & file structure for data, making it easier for users to organise/ find data in a systematic way

On networks/ shared computers file management is used to control file permissions

File permissions control who can delete the file. It is the OS that asks for confirmation when you try to delete a file


how do computers carry out logical operations on data and display it to the user

using the input-process-output model


name some input devices



name some output devices



describe what is meant by the input-process-output model

- data is entered into the computer and is manipulated according to the instructions of the program
- the results of the processing are then displayed to the user in a suitable form


a user has to log in to a network. describe this in terms of the input-process-output model

input: the user inputs their login info through a keyboard which is an input device
processing: the login name and password are processed by the computer and the CPU validates it by comparing it with data stored on the hard drive
output :if the login is unsuccessful and the data doesnt match that stored, a message will appear asking them to enter it again through the monitor which is a output device


a user has to log in to a network. describe this in terms of the input-process-output model

- input: the user inputs their login info through a keyboard which is an input device

- processing: the login name and password are processed by the computer and the CPU validates it by comparing it with data stored on the hard drive

- output :if the login is unsuccessful and the data doesnt match that stored, a message will appear asking them to enter it again through the monitor which is a output device


list 2 registers of the CPU with specific functions in the fetch decode execute cycle

program counter
memory address register


describe the role of the control unit in the operation of the CPU

coordinates the actions of the other components in the CPU and the whole computer by sending out control signals
- it also decodes the program instructions and executes them using the other components


explain how program instructions stored in computer memory are processed by the CPU

- during the fetch phase of the fetch decode execute cycle the CPU sends a signal to the main computer memory requesting the next instruction to be executed

- this instruction is decoded by the CPU and executed
if calculations are required these are carried out by the ALU


state the type of memory used to store application data during execution



state an advantage and disadvantage of RAM

+ data can be read from and written to RAM
-RAM is volatile so if you turn the power off data in RAM is lost


what is ROM

- used to sore instructions that dont nee to be changed during normal use


state an advantage and disadvantage of ROM

+ ROM is non volatil so it retains data even when the power is turned off
- data can only be read from ROM


state an advantage and disadvantage of ROM

+ ROM is non volatil so it retains data even when the power is turned off
- data can only be read from ROM


give 2 differences between RAM and ROM



what is cache memory

- very fast memory, usually within the CPU
- speeds up processing by storing recently/ frequently used instructions so they don't have to me fetched from the main memory


describe the role of programs stored in ROM



describe the diference between volatile and non volatile memory



explain the role of cache memory in a computer system