Computing paper 1

What is the CPU?

The part of the computer that executes program instructions to process data. It handles main memory and input-output operations

What is cache?

High-speed memory used to hold frequently used instructions, to improve processor performance. Quicker for the CPU to access instructions from the cache then from main memory/ RAM

What are the 4 registers?

ACC PC MAR MDR

What does the accumulator do?

Stores the results of any calculations made by the ALU

What does the Memory address register do?

Stores the address ofo data to be fetched from of the address of where data is to be stored

What does the Memory data register do?

Stores the data that is fetched/ read from memory to be processed

What does the program counter do?

Stores the address of the next instruction to be fetched from memory. It is incremented during the FDE cycle

What is a bus?

A communication pathway along which signals are transmitted

What are the 3 types of busses and what are their purposes?

AddressCarries address locations of stored data from the processor to main memory and input/output controllersDataCarries data to and from the processor, main memory, and input/output controllersControl Carries signals that coordinate the operation of the components

What is Von Neumann architecture?

Uses the idea of storing program instructions and data in main memory and moving them between memory and the processor when they were needed by the processor

How does clock speed affect CPU performance?

Clock speed measures how fast FDE cycles happen Measured in GHz (1GHz = 1 billion FDE's per second) Higher clock speed= quicker CPU

What are the dangers on an increased clock speed?

Overclocking- can overheat computer

How does the number of cores affect the performance of the CPU?

Core: ALU, CU, Registers More cores= multitasking, tasks done simeltaneously Parallel processing- single tasks split into 2 parts, each part processed at the same time

When can't parallel processing take place?

If tasks are sequential

How does cache size affect the performance of the CPU?

Cache stores frequently, recently or about to be used instructions Faster for CPU to access Cache- FDE becomes quicker

What is an embedded system?

A dedicated system that has a specific purpose Built on a curcuit board Has its own specific software and hardware called firmware

What are the advantages of an embedded system?

Efficient Reliable Easy to design Cheap to produce Compact in size

What are some examples of devices that use embedded systems?

Washing machines Smart watches Fitness trackers Vacuum robots

Why is main memory/ primary memory needed?

To hold data and programs that are currently in use. Can be directly accessed by the CPU

What is RAM?

Random access memory Stores programs and data currently in use and the operating system It is volatile Not very big- 1-2 GB More RAM= better computer performance

What does volatile mean?

Needs power to run/work

What is ROM?

Read Only Memory Stores: Boot program (sequence of instructions to start and load OS), BIOS (Basic Input Output Systems- checks everything is connected), MAC address (on network card) Provided by manufacturer Cannot be overwritten Small size- 1-2 MB

What is virtual memory?

When RAM is full, certain sections of the hard drive become VM. Can be accessed by the CPU, slower to access VM Volatile Data + programs in RAM that aren't in use get moved to VM OS swaps programs between RAM and VM

What is disk thrashing?

Constant switching between RAM and VM Causes loss of data and slows down computer

What is secondary storage?

Non volatile storage

What is the difference between memory and storage?

Memory Volatile Small capacity Accessed by CPU Storage Non volatile Large capacity Not directly accessed by CPU

What are the pros and cons of magnetic storage and what are some examples?

E.g. hard disk, floppy disk, magnetic tape Pros: Huge storage capacity, cheapest, can store data for long periods of time Cons: mag fields can corrupt/ damage data, not as portable (hard disk inside computer and physically larger), moving parts can degrade, slower to access

What are the pros and cons of optical storage and what are some examples?

E.g. CD, DVD, Blu Ray Pros: portable, cheap w/ small amounts of data, immune to mag fields Cons: media not as robust (disks can scratch), slower to write/ access from, expensive for large amounts of data

What are the pros and cons of solid state storage and what are some examples?

e.g. USB stick, SSD, memory card Pros: Portable, Robust (no moving parts), faster to access data (compared to magnetic hard disk) Cons: SSD's expensivce, limited number of write erase cycles

What are the characteristics of storage?

Capacity Speed Portability Durability Reliability Cost

Why should data be sotred in binary format?

Computers use transistors which are switches that can be switches on or off

What are the data sizes?

Bit Nibble- 4 bits Byte- 8 bits Kilo Mega Giga Tera Peta

What are the advantages of hexidecimal?

Large binary numbers are hard to remember Hex is easier to remember Hex used in error messages- Helps programmer find and fix problems

What is 10 in hex?

A

How to cobvert from denary to hex?

E.g. 44 to hex 44 put into binary: 00101100 Split binary in 2: 0010 1100 Convert binary nibbles to hex: 0010 = 2, 1100 = 12 = C

What are the bianry addition rules?

1 + 0 = 1 1 + 1 = 0 carry 1 1 + 1 + 1 = 1 carry 1

What is overflow?

When there is no room for carry/ result

What are binary shifts?

Multiplying and dividing Multiply- numbers move to left Divide- numbers move to right x/ ÷ by 2 means 1 shift by 4 means 2 shifts

What is compression?

Reducing the size of a file so that it takes up less storage space or bandwidth when it's transmitted, it's quicker to travel

Why is compression needed?

Takes up less storage Quicker uploads and downloads Takes up less storage on servers Smaller files reduce congestion on internet Makes audio and video files suitable for streaming

What lossless compression?

Nothing is lost Algorithm checks for redundancy- items that doen't need to be there Text files are eary to compress

What s lossy compression?

Decreases file size by permenantly removid data Not for text files Removes some pixels, deletes background noice/ silence etc.

What are the pros and cons of Lossy? Examples

Pros: Greatly reduced file size, takes up less nadwidth, common Cons: Loss is permenant, can't be used on text / software fileS, poorer quality than original but generally unnoticeable E.g. MP3, JPEG

What are the pros and cons of lossless? Examples?

Pors: data removal is temporary, can be decompressed, can be used on text and software Cons: slight reduction in size E.g. PNG, FLAC (audio)

What is the difference between Bitmap and Vectors?

Bitmap- Gets pixelated- page divided into an invisible grid, each pixel assigned a colour Vector- doens't get pixelated

What is a pixel?

Smallest dot on a computer screen, images made of pixels

What is the resolution?

Number of pixels in an image Higher resoloution = better quality but arger size

What is colour depth?

Number of bites used to encode the colour of each pixel 2^n = number of colours that can be stored, n = colour depth

Image file size formula

Width x height x colour depth

What is metadata and what are some examples?

Data about data Used to provide extra info Stored in EXIF (Exchangable image file format) E.g. Height, colour depth, camera lens type

What is sampling?

Making physical measurements at set time intervals and then convertig the mesaurements to digital values

Why is sampling used?

Converts sound to digital values

What is a sample?

A measure of amplitude at a specific time

How does sample rate affect the size and quality of the file?

Samples rate- number of times the sound is samples each second, in Hertz Higher samples rate = more accurate representation of actual wave and larger size

How does bit depth affect the size and quality of a the file?

Number of bits available to store each sound sample- typically 16 / 24 bits

What is the file size formula for an audio file?

Bit rate x length in seconds

What is the formula of bit rate?

Sample rate or frequency x bit depth or sample size x number of channels

What are the benefits of digital recording?

Can be editied/ manipulated easily More portable Can be played repeatdly without deterioration Can be copied on a computer

What is a character set

The list of binary codes that can be recognised by computers as being useable characters

What is ASCII?

Can store 256 characters- not enough for all langugaes 8 bit

What is Unicode?

32 Bit- enough for all languages Standard

What is a computer network?

Two or more computing devices connected together in order to share resources and exchange information

What does network enabled mean?

A device capable of joining a network

What is a LAN?

Two or more network enabled devices connected within a close geographical range. This can conver a business office or a few near by buildings e.g. a library or uni campus

How does a LAN work in a home?

Devices connec to a home hub - connects to ISP Home hub contains Wireless Access Point

What are the advantages of a LAN?

User can log on from any work station and still access their files Printers and photocopiers can be shared Resources and files can be shared by users to collaberate Backups can be done centrally rather than from each machine individually Malware checks can be done on server

What are the cons of LANs

Network failure- issue w/ file or internet server causes problem to all Slow service- lots of file requests/ jobs slows down, not enough bandwidth Virus + malware- virus on one workstation can affect whole network Cost- expensive to set up and run for large business networks Expert support required- many business networkds require specialist staff to deal w problems

What are some measures that can be taken to improve LAN security?

Passwords Access rights Audit log Backups Encryption Install software- users unable to do so

What is a WAN?

Connects 2 or more LAN's over a large geographical area Often hired out from major telecom companies

How are WAN's connected?

Fibre optics Satallite comms Leased telephone lines

What are the pros of a WAN?

Connects LANs Allows users to collaberate over a wide area Allows files and data to be shared between LANs

What are the cons of WANs?

Can be epxpensive to hire Failure of WAN is beyond company's control if the WAN is hired

Why are networks used?

Allows users to collaberate and communicate over large distance Enables internet to work

What is a stand alone?

A computer that not part of network, can only access data files/use preriphrals that are on or directly linked to that computer

What is a topology?

Describes how all the parts of a network are arranged and connected together

What is a star topology?

A network which the server/ central component/ switch is in the middle and cables run from each work station to the central device

What are the pros of a star topology?

Fast connections- dedicates connections Easy to trace faults Secure Easy to add to Cable faults may not affect all stations

What are the cons of a star topology?

Difficult and expensive to set up Dependent on central component - can get congested Needs managing

What is a mesh topology?

Each node relays all infromation recieved to all other nodes Info picked up by intended node or info sent along suitable pathway

What is a partial mesh topology?

One node will connect to all nodes or nearly all others but some will communicate directly with some others

What are the applications of mesh and why are they applicable?

Music straming devices around the home use mesh to maximise range within house Battlefield mesh networks allow communication between soilders Mobile hotspots Because of robustness of network, will always find alternative pathway

What are the pros of mesh topology?

Data can be trasmitted simeltaneously Highly robust as network will always find different routes Can handle high volumes of data Quicker- no need to travel via switch or hub Adding/ removing devices will not disrupt transmission

What are the cons of a mesh topology?

Expensive Impractical- lots of wires Difficult to expand and maintain (complex)

What is a network interface contoller?

Has its own MAC address MAC address enables devices on network to be uniquely identified ∴ allows data to be sent to correct device Converts data from nodes into format compatible with network (ethernet plugs into NIC)

What does a hub do?

STUPID (hubris) Small box, links all nodes together to form a network Transmit data packets to all other nodes

What are the pros and cons of a hub?

Pro: - cheaper Cons: - creates traffic - security risks - collided data is unuseable, must be retransmitted

What is a switch?

SMART Sends packets to intended node Identifies devices w MAC address Reads physical MAC address from data packets and sends in destination node

What are the pros and cons of a switch?

Pros: - less data collisions - better security Con: - expensive

What is a router?

Transfers data between networks, neeeded to connect to internet

What is architecture?

The layout of a network, describes the way in which computers and nodes are organised

Describe the Client Server architecture

A networking architecture where devices are designated as clients or servers. Clients make requests for services from servers that respond to these requests.

What is a server (client server architecture)

Specialist computer which is designed to allow multiple users to access it Performs tasks e.g. store and 'serve' files and resources to use when requested print jobs access to internet email servers data backups Large networks have multuple servers which are dedicated to perform specific tasks e.g. file server, email server, print server, web server Computer on network connect to server through hub or switch

What is a client (client server architecture)

- Sends requests to be processed by the server

What is authentication?

A security measure used to verify a user's identity and level of permissions Server asks user for username and password, checks if valid

What are the advantages of client server? same as LAN

Clients can request files stored on server, share resouces, access emails, use internet, have personal area not accessible to others on network Access files from any computer on network Backups are central Updates and installation done centrally

What are the disadvantages of client server?

Requires specialist knowledge to set up and maintain (e.g. Network Manager) Expensive to set up and maintain Users dependant on central server for files, resources etc.

Describe peer to peer architecture

Commonly found in homes and small businesses No central server, all nodes equal Files stored on hard disk of each computer Files can be shared to other users in network by shared permsissions or accessed through particular workstations

What are the advantages of peer to peer?

If one peer unavailable, others can still use network (CS architecture reliant on server) Peers can access files/ resources shared by others Easier to set up

What are the disadvantages of peer to peer?

Backups/ updates cannot be done centrally Less secure- only password used to protect files, if user knows password everything can be accessed (CS can have implemented security measures)

What is a WAP?

Wireless access pointEnables wireless devices to connect to a local network In a small wireless network (e.g. home) WAP built into the network access device (home hub, provided by ISP) Allows devices to connect wirelessly and may also allow two or three wired connections. In a larger network May find stand-alone WAP's - connected by cable to a switch that is part of a wired network