Flashcards
Giant Computing Test
Cards in this deck (94)
- 1The CPU What does The CPU do?The CPU
You can think of the CPU as being like the brain in a human
It is responsible for all of a computer’s processing - 2The CPU What is Von Neumann architectureThe CPU
Computer programs and the data the programs are using are stored in the same memory
Data then moves between the memory unit and the processor - 3The CPU Name the Registers in the CPUProgram Counter
ALU
Control Unit
General Purpose Registers - 4The CPU What is the Program Counter:Program Counter: A special purpose register that holds the address of the next instruction to be executed
- 5The CPU What is the General Purpose Registers:General Purpose Registers: Hold data, such as numbers during arithmetic calculations
Some architectures have just a single register called the Accumulator - 6The CPU What is The Program CounterThe Program Counter points to the next instruction that needs to be executed
It is located in the Control Unit
The Program Counter is incremented after fetching an instruction
This moves it on to point to the next instruction to be executed - 7The CPU What is The AccumulatorThe accumulator is where arithmetic and logic results are temporarily stored much like the M+ function on a calculator
Without the accumulator, it would be necessary to write the result of each calculation to main memory
The accumulator speeds up the storage and retrieval of calculations - 8The CPU What is The Arithmetic Logic UnitThe ALU or Arithmetic Logic Unit performs:
Logical operations,
shift operations and
arithmetic operations
Performs two sorts of operations on data:
Arithmetic operations
addition, subtraction, multiplication, division
Logical operations
comparing one data item to another: is it smaller than, greater than or equal to? - 9The CPU What are The Memory registers (Name them)With the von Neumann architecture, both the instructions and the data are stored together in RAM
Two registers are required to implement this:
Memory Address Register
Memory Data Register - 10The CPU What is Memory Address RegisterIt is a Memory register
The MAR holds the address of the current instruction being executed
The MAR knows the location of the data that needs to be accessed
It keeps track of where data is located - 11The CPU What is the Memory Data RegisterIt is a Memory register
The MDR holds the actual data that is being stored in RAM
It acts as a buffer and holds data that is copied from RAM, ready for the CPU to process it - 12The CPU How to the MAR (Memory Address Register) and MDR (Memory Data Register) work togetherMAR (Memory Address Register)
MDR (Memory Data Register)
The two work together; The MAR knows where to look for data in RAM, the MDR keeps hold of that data until it’s ready to be used by the CPU - 13The CPU What is The Control UnitThe control unit coordinates all of the activities taking place within the CPU
Much like the conductor of an orchestra
The control unit co-ordinates and controls all the operations carried out by the computer.”
Controls and monitors hardware attached to the system
Controls input and output of data
Controls the flow of data within the CPU - 14The CPU What is Fetch – Decode – ExecuteThe CPU operates by repeating three operations:
FETCH – causes the next instruction and any data involved to be fetched from main memory
DECODE – decodes the instruction
EXECUTE – carries out the instruction
Repeat… - 15The CPU What affects CPU performance?The following are three of the most common factors which can affect a CPU’s performance
Clock speed Cycles per second
measured in hertz
Processor cores The number of duplicate
processors linked together on a single chip
Type and size of memory
Cache size
Superfast working memory - 16The CPU Explain Processor SpeedOne cycle per second = 1 Hertz (Hz) = 1 instruction carried out each second
1 Kilohertz (KHz) = 1000 cycles per second
1 Megahertz (MHz) = 1,000,000 cycles per second
1 Gigahertz (GHz) = 1,000,000,000 cycles per second - 17The CPU Explain Multi-core processorsA dual-core processor has two processors in the same integrated circuit, linked together
A dual-core processor has twice the power but does not always perform twice as fast, because the software may not be able to take full advantage of both processors
A quad-core processor has four linked processors - 18The CPU Explain Cache memoryCache is a small amount of very fast, expensive memory in the CPU
It can be accessed faster than regular main memory (RAM) - 19The CPU Explain Levels of cache memoryLevel 1 cache is extremely fast but small (between 2-64KB), located very close to the processor
Level 2 cache is fairly close to the processor, fairly fast and medium-sized (256KB-2MB)
Some CPUs also have Level 3 cache, relatively large and close to RAM - 20The CPU Explain The benefits of cacheThe data used most often by the CPU is held in Level 1 cache so is instantly available
In most systems, other data needed by the CPU is accessed from the Level 2 cache 95% of the time
This greatly reduces the time that the CPU has to wait for data from main memory
The size of the Level 2 cache, and whether it is actually on board (on the CPU) is a major factor in determining the performance of the CPU - 21The CPU Explain Embedded systemsAn embedded computer is a single microprocessor that includes RAM, ROM and a CPU
An embedded computer is frequently used to control a device using simple controls
Without embedded systems, a digital device would not be able to perform specific functions
For example, a dishwasher wouldn’t know how to heat the water, or a satnav wouldn’t know how to communicate with a satellite - 22Memory Explain The Types of primary memoryThere are many types of memory used in computers
The two mains types are:
RAM (Random Access Memory)
ROM (Read Only Memory) - 23Memory Why is RAM required?When an application or the operating system is run, it is copied from the hard disk into RAM
It is fast. - 24Memory Explain RAM useIs often referred to as:
main memory, primary memory, central memory, core memory
It can be read from and written to
Access to RAM is very fast
At any one time it will normally contain:
The Operating System (or part currently in use)
The software currently in use
The data which the software is using - 25Memory Describe RAMThe computer stores running programs and data in RAM when your computer is turned on
When your computer is off, RAM is empty as it is volatile
All your programs and data are safe on your hard disk - 26Memory What happens when you run out of space in RAMYou use Virtual memory
- 27Memory Describe ROMRead Only Memory
This type of memory is Non-Volatile
Computing bootup instructions (Bootstrap) are stored in it.
Read Only - 28Storage Are secondary storage devices volatile or non-volatile?Secondary storage is non-volatile – it keeps its content when the power is switched off
- 29Storage Explain uses of secondary storagePrograms and data are stored on hard disk
CDs may be used to distribute software, music, e-books etc.
Memory sticks may be used to transport data from one place to another
Magnetic tape or external hard drives may be used for backup - 30Storage Name Storage typesPrimary storage
RAM and ROM
Secondary storage
Hard Disk Drive (HDD)
Solid State Drive (SSD)
Offline secondary storage
Compact Disc (CD) or Digital Versatile Disc (DVD) or BluRay
USB Flash memory
Removable HDD
Magnetic tape - 31Storage Describe Storage methodsMagnetic: Mechanical parts move over the disks surface to read and write data magnetically
Optical: Lasers read and write data using light
Solid State: Data is recorded onto solid memory chips without any moving parts - 32Storage Describe Magnetic disksBasic features:
Disk contains concentric circles called tracks
Each track is divided into sectors
Disk heads mounted on mechanical arms read and write the data - 33Storage Describe the some of the uses of Magnetic disksFixed hard drives are built into virtually all PCs and laptops
They have a very large storage capacity, up to 6TB or more
Portable hard drives can be connected to a computer via a USB port
They are used for backing up or transporting data
Some portable music players have tiny hard drives no bigger than a small coin
They can store several GB of data - 34Storage Describe the Advantages: and Disadvantages of Magnetic storageAdvantages:
Cheap, vast storage capability, fast write speed
Disadvantages:
Lots of mechanical parts, durability an issue, sealed unit due to disk head and platter precision and not very portable
Uses:
Personal computers, storage of vast quantities of data
Capacity:
500GB - 6TB or greater - 35Storage Describe Optical storageBasic features:
Data is stored as pits and lands burnt into a spiral track circulating outwards from the centre
A laser beam passes over the pits and lands the level of reflection is measured
From this signal, 0s and 1s can be derived from reflections or no reflections - 36Storage Describe the Advantages: and Disadvantages of Optical storageAdvantages:
Cheap, very easily portable, takes up little space physically
Disadvantages:
Less storage capacity compared to other types
Easily damaged / scratched, requires a CD reader
Slow write speeds
Uses:
Songs, videos and other multi-media storage, backup and archiving of data
Capacity:
CD-ROM – up to 720Mb
DVD – up to 8.4Gb
Blu-Ray – up to 50Gb - 37Storage Why are the capacities of CDs, DVDs and BluRay different given they are all the same physical size?The Pit size and laser wavelength
is diffrent. - 38Storage Describe Solid State Drives (SSD)Basic features:
Solid-state disks use non-volatile flash memory to store information
Very fast burst read/write speeds due to data being physically close and easy to recover
No mechanical or moving parts - 39Storage Describe the Advantages: and Disadvantages of Solid State Drives (SSD)Advantages:
Highly durable, no moving parts, very fast read/write speeds, no noisy fan, faster start up times
Disadvantages:
Expensive at present, less storage capacity / physical size than traditional hard disks
Uses:
Hand held computers
Military usage
Capacity:
100GB – 16TB - 40Storage Describe uses of Flash memoryLow cost, portable, no moving parts, durable
This makes them ideal for a range of offline devices:
Cameras
Mobile phones
USB memory sticks - 41Storage How does flash memory workLarge electric current used to force electrons through a barrier and trap them on the other side
They remain on the other side until “flashed” with a new current, hence the name
Trapped (charged) or not trapped = 0 or 1 - 42Storage Explain Cloud storageCloud storage refers to saving data in an off-site storage system maintained by a third party
Examples include example Dropbox and Google Drive
Instead of saving data on your computer's hard drive or other local storage device, you save it to a remote database, and access it via the Internet - 43The Internet What is a Wide Area NetworksAny network in which the computers communicate using resources supplied by a “third party carrier”, such as British Telecom, is a WAN
A WAN uses cables, telephone lines, satellites and radio waves to connect, usually spread over a wide geographical area
The Internet is a Wide Area Network (WAN)
Can you name some organisations that are likely to have their computers linked in a WAN? - 44The Internet What are IPv4 addresses and IPv6 addressesLike every front door in the world, every network in the world has a separate, unique address
There are now so many computers that the number of available IPv4 addresses is running out
A new IPv6 system of addressing is replacing IPv4
Eg: 72.129.214.16 - 45The Internet What is A circuit switching network and why aren't they usedWhen you make a telephone call, a dedicated connection is set up between you and the person you are calling for the duration of the call
This is called “circuit switching”
It works fine for phone calls, but there could never be enough lines for all the billions of people sending data across the Internet - 46The Internet Explain Packet switchingSuppose you want to send a file of 3Mb across the Internet
The file is broken up into data “packets” of 512 bytes - 47The Internet Every computer and other device connected to the Internet has an address. What is this.Every computer and other device connected to the Internet has an IP address
E.g. 81.101.137.12
Packets are labelled with the sender’s and the destination IP addresses
Packets are sent across the Internet separately via different routes and reassembled at the end - 48The Internet What does each packet contain.The IP (Internet Protocol) address it is going to
The IP address it has come from
The sequence number of the packet
The number of packets in the whole communication
Error checking data - 49The Internet What happens when a packet is recivedThe recipient computer re-orders the packets into the correct order
Each packet is checked for errors
Corrupt packets are requested to be resent
The recipient computer will acknowledge receipt of packets
Any packets not acknowledged after a set time interval will be automatically resent by the sending computer - 50The Internet What is the job of a routerEach node is a crossroads and requires something to direct data packets to their destination along the path which is least busy at that moment
This is the job of a router - 51The Internet Explain the Domain Name System (DNS)DNS technology allows you to type a name such as google.co.uk into your web browser
It translates the web address google.co.uk into an IP address
e.g. www.google.co.uk = 74.125.131.94 - 52The Internet What are DNS serversThere are 13 DNS “root” servers worldwide which keep a complete database of all names and IP addresses
Other DNS servers lower down the hierarchy hold parts of the database
When a DNS server receives a request not in its database, it will pass the request on to another server until it reaches one with the matching name and IP address
Lower level DNS servers are owned by ISPs - 53The Internet Can your IP address changeIf you use a laptop at home, its IP address is the one belonging to the router at home
But if you take the laptop on holiday and use it at the airport or in Tenerife, your IP address doesn’t go with you - it will change each time you move from place to place - 54The Internet Explain MAC addressingA Media Access Control (MAC) address is assigned to each Network Interface Card (NIC) by the manufacturer
Your computer may have more than one MAC address, e.g. one for ethernet and one for wireless
And a mobile phone may have two different MAC addresses – one for wireless and one for bluetooth
A MAC address looks like this:
3B:14:E6:39:0A:2C
Every networked device in the world has a unique MAC address - 55The Internet What is a LAN?LAN stands for Local Area Network
A LAN operates on a single site such as a school or small business using their own cabling systems - 56The Internet What are the advantages of connecting together computers in a LAN?Advantages
Sharing resources such as printers saves money
You can access your files from any computer in the network
Data is easy to back up as it is stored centrally on the server - 57The Internet What are the Disadvantages of connecting together computers in a LAN?Disadvantages
Purchasing the network hardware is expensive
Managing a large network is complicated
Viruses may be able to infiltrate the network and infect every computer - 58The Internet What are the Advantages of a Star networkAdvantages
Fast data transfer as there are fewer data collisions
If one cable fails the other workstations are not affected - 59The Internet What are the Disadvantages of a Star networkDisadvantages
Requires additional hardware such as the central switch
If the central device fails the whole network goes down - 60The Internet What is the Difference between a Full Mesh network and a Partial Mesh networkIn a Full Mesh network not every computer is connected
- 61The Internet What is Mesh networkingNodes act as routers for data in order to relay and propagate data in the network
Partial mesh network model usually used, often in conjunction with star topologies to create larger networks - 62The Internet What are Wireless mesh networksWireless mesh networks have enormous potential to provide Wi-Fi solutions for entire organisations, cities or even countries
Only one node needs a wired Internet connection – no other cabling or infrastructure is required
The more nodes that use the network, the more the signal can travel
A node within broadcast distance of three other nodes, will have triple the standard bandwidth
As the distance between one node and another is halved, signal strength becomes four times stronger - 63The Internet What are the Advantages of a Star networkNo single point of failure – It is a self-healing network
Expansion and modification can be done without disrupting the network
Data can be transmitted from different devices simultaneously - 64The Internet What are the Disadvantages of a Star networkCan involve redundant connections
Expensive to install cabling if using wired connections
Network maintenance and administration is difficult - 65The Internet Name some Network hardwareA Network Interface Card (NIC) in your computer or device
A router or switch, which provides access to a local area network
A modem may also be combined with the router in a single device - 66The Internet What are Routers, hubs and switchesRouter
Sends data packets on their way in the best direction
Hub
Central, multi-plug adaptor for computers and printers in a network
When a packet of data is received, it broadcasts the packet to all devices on the network
Switch
Smart multi-plug adaptor only sends packets to the intended recipient, using its MAC address
Reduces network traffic and increases speed - 67The Internet What are Ethernet protocolsEthernet’ refers to a family of standard local networking ‘protocols’ or rules
It describes how devices should format data ready for transmission between computers on the same network
Similar to polite human conversation, nodes will wait until the connection is quiet before attempting to ‘speak’ or transmit
Two nodes attempting to transmit simultaneously will stop and each wait a random period before reattempting - 68*network L2*q
- 69The Internet What are the types of Ethernet cableThe Ethernet networking standard uses twisted pair cabling or fibre optics
- 70The Internet How does Ethernet transmission workEthernet systems divide data into frames, (similar to Internet packets)
Frames are broadcast to all nodes – only the intended recipient will open the frame. Others will be discarded
Frames which are detected to contain transmission errors are dropped or resent - 71The Internet What are Virtual networks?Logical segments of a larger physical network (e.g. the Internet) are configured to behave as though they are part of a separate, and much smaller network
Transmission is encrypted since data is travelling across a space used by others - 72The Internet Where could you find a Wireless NICsBuilt into every networked device capable of connecting to a wireless network
These include:
PCs
Smart phones
Wireless speakers - 73The Internet What is a Wireless access pointA wireless Access Point (AP) is a device that allows wireless devices to connect to a wired network using Wi-Fi
The AP usually connects to a router (via a wired network) as a standalone device, but it can also be an integral component of the router itself - 74The Internet What are Wi-Fi Frequencies and channelsThe 802.11 standard uses five frequencies:
2.4GHz, 3.6 GHz, 4.9 GHz, 5 GHz, and 5.9 GHz
Each frequency is subdivided into various channels:
Each channel has a central frequency and bandwidth - 75The Internet 802.11 standards 2.4GHz AdvantagesGreater range and coverage
- 76The Internet 802.11 standards 2.4GHz DisadvantagesMore interference from other devices, and only three non-overlapping channels
- 77The Internet 802.11 standards 5GHz AdvantagesLess crowded space with 23 non-overlapping channels with higher data transmission rates
- 78The Internet 802.11 standards 5GHz DisadvantagesFewer devices can use the 5GHz frequency, less able to penetrate through walls
- 79The Internet What is EncryptionEncryption is the encoding of data so that it can no longer be easily understood
The process of converting plaintext into ciphertext - 80The Internet What is Plaintextthe original message to be encrypted
- 81The Internet What is Ciphertextthe encrypted message
- 82The Internet What is a Keya sequence of numbers used to encrypt or decrypt, often data using a mathematical formula
- 83The Internet What is an Encryption algorithmthe formula for encrypting the plaintext
- 84The Internet What the encryption Two inputsplaintext and a secret key
- 85The Internet What are common Encryption techniquesPrivate key (Symmetric encryption)
Public key (Asymmetric encryption) - 86The Internet What is Private key (Symmetric encryption)A single key is used to encrypt and decrypt a message and must be given to the recipient of your message to decrypt the data
- 87The Internet What is Public key (Asymmetric encryption)Two keys are used - one to encrypt and the other to decrypt data
This is more secure as it means that you never have to send or reveal your decryption key - 88The Internet What is a Caesar shift cipherThe earliest known substitution cipher was invented by Julius Caesar
Each letter is replaced by the letter n positions further on in the alphabet
n is the key and is used to encrypt and decrypt the message.
This is symmetric encryption - 89The Internet What is CryptanalysisThe objective of cryptanalysis is to decode the ciphertext – typically by finding out the secret key
- 90The Internet What are the approaches for CryptanalysisBrute-force attack
Non-brute-force attack (cryptanalytic attack) - 91The Internet What is a Brute-force attack on encrypted dataEvery possible key is tried
On average, half of all possible keys need to be tried, so the longer the key, the more time it takes to find it
The Caeser Cipher uses a shift of between 1 and 26 assuming only uppercase letters of the alphabet are used
This means that there are 26 possible keys requiring an average of about 13 tries to crack the code - 92The Internet What is Key strength for an encrypted set of data5 bits would enable 25 key combinations; one for each letter (plus a few spare) so it could be said that Caesar was using 5-bit encryption
Increasing the number of bits used for a key, increases the strength of the encryption - 93The Internet What is a Non-Brute-force attack on encrypted data exampleIdentical parts of messages.
Letter Frequency analysis - 94Wireless L3 frequ an
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- GCSE Computing Flashcards on Giant Computing Test, created by Sam Houghton on 08/03/2017.
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