Mapa mental
Computer revision
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Computer revision
Computer systems
- CPU
- Clock speed - This is how many actions the processor does per second. This is measured in MHz/GHz. 1MHz = 1,000,000 action per second. The faster the clock speed the more actions the CPU can do per second, and in turn the faster the CPU.
- Cores - The number of cores increased the speed of the CPU. Each core adds more clock speed but each core has to communicate with each other using channels meaning some of the extra speed is used to communicate. Clock speed*cores = speed of the CPU.
- Cache = Cache acts as a buffer between the CPU and RAM. This is a small amount of storage which is very fast to access. This store data which is most likely to be reused such as website names and login details. Each core has its own L1 Cache(cache stored on the CPU chip). Cores may also share L2/3 cache(Cache stored between the CPU and RAM)
- Storage
- Virtual memory - This is secondary storage that temporarily works as RAM. This happens when there is not enough RAM to hold all the open data. Virtual memory is slower a it spends time moving the data rather than just executing instructions.
- RAM/ROM
- RAM -Random access memory. This is volatile memory. This store currently open programs and applications.
- ROM - Read-only memory. This is non volatile. This stores the boot up sequence.
- Difference between RAM/ROM - RAM loses data when turned off. This is because it is volatile. ROM doesn't lose data when turned off and is non volatile.
- PROM - Programmable read-only memory. This is bought cheaply and directly programmed on by programmers. This can not be rewritten.
- EEPROM - Electrically erasable Read-only memory. This is usually used in smartphones and PCs because it can be rewritten on and programmers can easily update the firmware.
- Storage types
- Magnetic - This is read through the levels of magnetism on the discs. This is usually very cheap per GB however it is not very portable, durable, or fast
- Optical Storage - This is read by a laser. The disk usually has a pattern which can be read back by a laser. This is usually stored on things such as a CD or DVD. This is usually a cheap form of storage and is very portable.
- Solid State Drive - This is read through logic gates. This uses binary to read 1s and 0s, on and off. This is usually in the form of a Solid State drive. This form of storage is usually the most expensive and best type. This is very reliable, portable and durable however it is very expensive per GB.
- Flash Data - Flash Data holds data when there is no power. This is non volatile memory. This is usually used in digital cameras, USBs and Video games. This is similar to EEPROM.
- Flash memory - is a type of non-volatile ROM called EEPROM
- Embedded Systems - This is a computer system with a dedicated function within a larger mechanical or electrical system. Examples - Microwave, Smart TV, Printer, Calculator.
- CPU
A constant Does not change its value. A variable does.
Sound
- 1. A microphone records sound in an analogue sound wave
- 2. The sound wave values is turned into voltage.
- 3. The sound card converts the sound from analogue to digital. This is done by sampling the sound. At each sample the sound waves value is recorded. The higher the sample rate the higher the sound quality is.
- 2. The sound wave values is turned into voltage.
- Higher sample rate = higher sound quality
- Sample rate is how many samples of the sound is recorded per second. This is measured in Hz. A CD has a sample rate of 44100/48000 KHz
- 1. A microphone records sound in an analogue sound wave
Compression
- Lossy
- Lossy compression loses data from a file in order to reduce the file size.
- This could be done by reducing the amount of colours(colour depth) in an image or by reducing the amount of samples in audio.
- The problem is that this reduces the quality of the file
- Some types of lossy compression could be JPEG and MP3.
- The problem is that this reduces the quality of the file
- This could be done by reducing the amount of colours(colour depth) in an image or by reducing the amount of samples in audio.
- Lossy compression loses data from a file in order to reduce the file size.
- Lossless
- Lossless compression doesn’t lose any of the data from the file.
- This means that the file loses no quality and it is the same as the original.
- This is done by using algorithms which find patterns in the files that are repeated.
- Zip files are one type of lossless compression.
- The problem is lossless compression doesn’t make the file as small as lossy compression.
- Zip files are one type of lossless compression.
- This is done by using algorithms which find patterns in the files that are repeated.
- This means that the file loses no quality and it is the same as the original.
- Lossless compression doesn’t lose any of the data from the file.
- Lossy
File sizes
- Bit
- Nibble
- KB
- MB
- Byte
- GB
- TB
- PB
- Smallest
- Largest
Binary And Hexadecimal
- 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
- 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
- 8, 4, 2, 1, 8, 4, 2, 1
- 0, 0, 0, 0, 0, 0, 0, 0
Disability help - using Computers
- Output
- High contrast mode to help colour blind users to see the screen more clearly.
- Magnifier to allow visually impaired users to see the screen more clearly
- Text-to-speech to allow blind users to hear the output.
- Braille printer to allow blind users to read documents.
- Input
- Puff-suck switch to allow mobility impaired users to blow or such through a tube. This could be used to click a mouse button
- Simplified/concept keyboards that user braille or larger keys.
- Eye tracking input which follows the movement of the user. This could be used to control a mouse on the screen.
- Output
Software
- Antivirus
- This scans your computer periodically to check any software which contains code which may harm the computer
- This also removes/ quarantines any harmful programs, it also notifies the user.
- This prevents some programs from being installed. This protects the computer by making sure the important files (boot up sector or operating system) are not changed.
- This also removes/ quarantines any harmful programs, it also notifies the user.
- This scans your computer periodically to check any software which contains code which may harm the computer
- Disk Disfragmenter
- Moves (part of) files around so that all parts of the files are stored together.
- This allows files to be accessed more quickly. Free space is collected together allowing larger files to be stored easily.
- Moves (part of) files around so that all parts of the files are stored together.
- Antivirus
network systems
- Topologies
- star
- Ring
- Bus
- Mesh
- A mesh network is a LAN where each node is connected to many other, configured to allow connections to be rerouted around broken or blocked path, with the signal hopping from node to node until it reaches its destination. Mesh networks are self-healing and very reliable.
- Pros:
- Cons:
- It is very expensive to use a mesh network - Lots of cable
- Building and maintaining a mesh network is very difficult and time consuming
- The chance of unneeded connections is high - Reduced efficiency, high costs.
- Building and maintaining a mesh network is very difficult and time consuming
- It is very expensive to use a mesh network - Lots of cable
- They are self-healing - If one node fails another will take its place.
- Can handle a high amount of traffic - multiple devices can transmit data simultaneously.
- Packets don't need to run back to a central server - Faster Packet transfer
- Can handle a high amount of traffic - multiple devices can transmit data simultaneously.
- Cons:
- Pros:
- A mesh network is a LAN where each node is connected to many other, configured to allow connections to be rerouted around broken or blocked path, with the signal hopping from node to node until it reaches its destination. Mesh networks are self-healing and very reliable.
- A bus topology has one main cable. Each node connects to this cable. There is a terminator on each end the main cable
- Pros:
- Cons:
- Data collisions are more likely when there are many nodes
- Depends on central cable, if it breaks the network breaks
- Low security as all computers receive the signal from the source.
- Requires terminators to dump signals
- Low security as all computers receive the signal from the source.
- Depends on central cable, if it breaks the network breaks
- Data collisions are more likely when there are many nodes
- Easy to setup and extend a bus network
- Uses a little amount of a cable.
- Cheap to setup
- Easy to set up small LAN networks
- Cheap to setup
- Uses a little amount of a cable.
- Cons:
- Pros:
- Mesh
- Each computer is connected in a ring. One computer to the next
- Pros:
- Cons:
- Each packet must pass through each computer
- If one node breaks so does the entire network
- The network is dependent on the cable
- If one node breaks so does the entire network
- Each packet must pass through each computer
- Computers have equal access and rights
- Very organised and reduces amount of data collisions
- No need for a network server to control connections
- Works well with many workstations
- No need for a network server to control connections
- Very organised and reduces amount of data collisions
- Cons:
- Pros:
- Bus
- A star topology uses a hub/switch in the centre. Every other node is connected via one cable to the centre
- Pros:
- Cons:
- If the central hub/switch/server breaks then the whole network stops working.
- The use of a hub/server/switch increases the overall cost of the network
- If the central hub/switch/server breaks then the whole network stops working.
- Easy to install wire
- No disruptions to the network when connecting or removing devices
- Workload is spread across all nodes. If one node breaks then the system still works
- No disruptions to the network when connecting or removing devices
- Cons:
- Pros:
- Ring
- star
- LAN
- WAN
- A Wide Area Network is created when LANs are connected. This requires broadband cables. This can connect organisations based in different areas.
- A Local Area Network is a network of computers within the same building.
- Client server
- Peer-to-peer
- In a p2p network each user has a part of the data. When a user requests for the data everyone sends the data sharing the workload.
- All users have equal access
- No control over the network. Anyone can set up
- Clients are not dependent on a central server
- If a machines on the network are slow then they will slow down other machines
- Each computer has to be backed up. Data can easily be deleted by users.
- If a machines on the network are slow then they will slow down other machines
- Clients are not dependent on a central server
- No control over the network. Anyone can set up
- All users have equal access
- Network harware
- NIC (Network interface controller)
- This connects a computer to a network.
- Router
- A router can form a LAN by connecting devices within a building. It makes it possible to connect to the internet wireless.
- WAP (Wireless Access Point)
- These are required to connect to a network wirelessly. Usually built in a router
- Internet connections
- Wireless connections
- Wireless connections use radio signals to send data across networks
- The wireless adapter converts the data into a radio signal and the wireless receiver decodes i so that the computer can understand it.
- Advantage
- Disavantage
- Interference can occur
- The connection is not as stable as wired networks and can drop off
- It will lose quality through walls or obstructs
- More open to hacking
- Slower than wired networks
- More open to hacking
- It will lose quality through walls or obstructs
- The connection is not as stable as wired networks and can drop off
- Interference can occur
- Cheap to set up
- Not tied down to a specific location.
- Can connect multiple devices without the need for extra hardware
- Less disruption to the building due to no wire being installed
- Can connect multiple devices without the need for extra hardware
- Not tied down to a specific location.
- Disavantage
- Advantage
- The wireless adapter converts the data into a radio signal and the wireless receiver decodes i so that the computer can understand it.
- Wireless connections use radio signals to send data across networks
- Protocols
- TCP/IP
- Transmission control protocol - Allows two computers establish a connection.
- Internet protocol - A set of rules for communicating over the internet.
- Transmission control protocol - Allows two computers establish a connection.
- A set of rules for how messages are turned into data packets and sent across networks,
- IP address
- A unique address for each computer device on a network
- SMTP
- Simple mail transfer protocol - used to send emails between servers
- POP
- Post office protocol - used to retrieve email from a server
- VOIP
- Voice over internet protocol - a protocol used for communication over voice data over the internet
- FTP
- File transfer protocol - a protocol used to transfer large files across the internet
- HTTP
- Hypertext transfer protocol - a request/response standard. Web browsers send requests and websites or servers respond to requests.
- TCP/IP
- Wireless connections
- Internet connections
- These are required to connect to a network wirelessly. Usually built in a router
- WAP (Wireless Access Point)
- A router can form a LAN by connecting devices within a building. It makes it possible to connect to the internet wireless.
- Router
- This connects a computer to a network.
- Modem
- A modem connects the router to your the internet. The modem between analogue and digital systems.
- Hub
- A hub sends data to all the devices on a network. This could be bad as no all devices need the data.
- Hub
- Switch
- A switch is similar to hub, however, the switch is more powerful as it stores the mac addresses of devices to that it can send data to specific devices.
- Bridge
- A bridge is used to connect separate LAN systems. A computer can act as a bridge through the operating system. A bridge looks for receiving devices before it sends a message to the device
- Bridge
- A switch is similar to hub, however, the switch is more powerful as it stores the mac addresses of devices to that it can send data to specific devices.
- A modem connects the router to your the internet. The modem between analogue and digital systems.
- Computer sorting/terms
- Bubble sort - used to sort numbers in order.
- 7. if the end is reached without swapping then the algorithm can stop and the list has been sorted.
- 6. if any numbers were swapped then repeat from step 1.
- 5. Repeat step 2 and 3.
- 4.Move to the next number in the list, make this the current number.
- 3. Is the next number smaller? If yes then switch them around. If not keep the same
- 2. Compare the current number with the next number.
- 1. look at first number in the list
- 2. Compare the current number with the next number.
- 3. Is the next number smaller? If yes then switch them around. If not keep the same
- 4.Move to the next number in the list, make this the current number.
- 5. Repeat step 2 and 3.
- 6. if any numbers were swapped then repeat from step 1.
- Merge sort
- merge the pairs until the entire list has been merged in order(similar to bubble sort)
- Combine 2 numbers and put them in order (do with the rest of the numbers)
- divide the list until it cant be divided more
- Combine 2 numbers and put them in order (do with the rest of the numbers)
- merge the pairs until the entire list has been merged in order(similar to bubble sort)
- 7. if the end is reached without swapping then the algorithm can stop and the list has been sorted.
- Abstraction - Taking away the unneeded information.
- Decomposition - Breaking down a problem to make it easier to solve.
- Algorithmic thinking - Following the needed steps in order to get to the many solutions.
- Decomposition - Breaking down a problem to make it easier to solve.
- Sequencing - A set of actions that follow on from one another.
- Selection - A decision within a program when a program decides to move based on the results of an event.
- Iteration - A single pass through a set of instructions .
- Casting - is the changing of the data types, and telling the compiler that you acknowledge the data loss.
- Iteration - A single pass through a set of instructions .
- Selection - A decision within a program when a program decides to move based on the results of an event.
- Code
- High-level language
- Requires a translator
- Portable
- Easier to read, write and maintain as commands are similar to English
- Uses data types and data structures, selection statements and repetition/iteration constructs.
- Uses logic operations and functions that are built into language.
- High-Level languages require translator software that will be held in RAM when a program is executed. It is the translator software that will take the high level language and translate it into executable code. Executable code is in binary form and can be understood by the processor. In low-level language there is no one to one conversion between code and binary instructions.
- Uses logic operations and functions that are built into language.
- Uses data types and data structures, selection statements and repetition/iteration constructs.
- Easier to read, write and maintain as commands are similar to English
- Portable
- Requires a translator
- Low-level language
- Low-level languages are hard to learn
- optimisation of code
- where no translator software exists
- greater control of hardware features, eg. small embedded computers
- where no translator software exists
- Why its used:
- optimisation of code
- Low-level languages are hard to learn
- Assembler
- Low-Level languages generally allow for a one to one conversion into machine code
- Hex notation is a low-level language
- Assembly code is a low-level language
- Assembly language is architect dependent and closely related to the hardware.
- Assembly code is not fully portable because of architecture dependence
- Assembly code needs to be converted to binary using an assembler
- Assembly code is not fully portable because of architecture dependence
- Assembly language is architect dependent and closely related to the hardware.
- Assembly code is a low-level language
- Hex notation is a low-level language
- Low-Level languages generally allow for a one to one conversion into machine code
- Compiler
- Interpreter
- Translates into machine code one line at a time.
- As soon as a line has been translated, it is executed
- If there is an error the interpreter will not move on to translate the next line - Good for finding errors
- Interpreter software is present in main memory during each execution of the program and for the execution of every line. - This means an interpreter is not as efficient as a complier
- Good for finding errors
- Can't tell what error, but can tell which line it is on.
- Good for finding errors
- Interpreter software is present in main memory during each execution of the program and for the execution of every line. - This means an interpreter is not as efficient as a complier
- If there is an error the interpreter will not move on to translate the next line - Good for finding errors
- As soon as a line has been translated, it is executed
- Translates into machine code one line at a time.
- Translate source code into object code.
- The compiler is held in RAM for the time it takes to translate the source code into object code.
- Compilers translate all of the code first.
- They do not execute the code. They store the object code in a file that can be executed after translation.
- Using a compiler once to create object code makes run time more efficient, but if there are an errors then it will not run. It will need to be re-compiled
- They do not execute the code. They store the object code in a file that can be executed after translation.
- Compilers translate all of the code first.
- The compiler is held in RAM for the time it takes to translate the source code into object code.
- Interpreter
- High-level language
- Bubble sort - used to sort numbers in order.
- NIC (Network interface controller)
- In a p2p network each user has a part of the data. When a user requests for the data everyone sends the data sharing the workload.
- A client server is where a client is dependent on the server to provide and manage the information.
- Not every user has equal access
- The server manages the network and needs a team of people to manage the server
- Clients are dependent on the server.
- The server can be upgraded to be made more powerful to cope with high demand.
- Data is all backed up on the main server
- The server can be upgraded to be made more powerful to cope with high demand.
- Clients are dependent on the server.
- The server manages the network and needs a team of people to manage the server
- Not every user has equal access
- Peer-to-peer
- Client server
- WAN
- Topologies
Software
- System software
- System software: software designed to change the way the system runs. Provides a platform for other software.
- Application software
- Software that runs to complete a task to benefit the user. Games, applications, editing software...
- operating system
- To boot up the computer. Manages hardware and resources for the computer. Provides an interface between software and hardware.
- utility software
- Designed to analyse, configure and optimise or maintain a computer, eg adtivirus
- Disk clean-up
- Free up disk space, deletes unwanted files or files that have not been used for a very long time
- open source software
- Free
- Users have the right to copy modify and share the product.
- Depends on the community to contribute to updates.
- Users can switch to alternate software or modify the software.
- Depends on the community to contribute to updates.
- Users have the right to copy modify and share the product.
- Free
- custom written software
- Specially developed software which is made for a specific purpose. This is usually expensive.
- proprietary software
- Paid (unless its free)
- Users cannot copy, modify or share the product.
- Users rely on the developers to update the product.
- The developers have complete control of the software and choose when and how to change the software.
- Users rely on the developers to update the product.
- Users cannot copy, modify or share the product.
- Paid (unless its free)
- off the shelf software
- This is commercial software which is available for sale to the general public. This is usually a packaged software solution for businesses.
- Defragmentation
- Reduces the amount of splits(Fragments) in a storage device. The maintenance of files.
- System software
Información
- Descripción
- Mapa Mental sobre Computer revision, creado por Jacob Alexander-Rothwell el 17/11/2017.
- Creado por
- Jacob Alexander-Rothwell
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