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Keyword
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Definition
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Example(s)
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Operating Systems
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Software loaded by the computer following the initial boot-up which controls both the hardware and software, incuding the processor, memory, I/O devices, and security.
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Windows 10, macOS
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Systems software
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Software that controls the operation of hardware in a computer.
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Application software
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Programs designed for the user to use to perform a specific task(s).
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Internet Explorer, Microsoft Word
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Utility Programs
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A type of systems software that manages the computer's resources
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Defragmentation, file encryption
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Logic Gate
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Truth Table
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AND
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x y z
0 0 0 1 0 0 0 1 0 1 1 1 |
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OR
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x y z
0 0 0 1 0 1 0 1 1 1 1 1 |
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NOT
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x z
1 0 0 1 |
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Component
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Purpose
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Central Processing Unit (or CPU)
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Processes data and instructions and make decisions. It is composed of many components (e.g. the CU, the ALU).
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Control Unit (or CU)
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Controls the operation of the ALU, memory and I/O devices; tells them how to respond to instructions it has fetched and decoded.
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Arithmetic Logic Unit (or ALU)
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Carries out arithmetic and logical operations. Results are stored in a register.
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Clock
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A crystal that vibrates at high speeds, dictating how many times a second the fetch-decode-execute cycle can be carried out.
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Bus
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Transports data and instructions around the CPU.
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Register
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Storage areas in the CPU.
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Main Memory
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Any form of memory directly accessible by the CPU (excl. cache, registers).
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Cache
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Small, fast memory that is close to the CPU. Stores data that is used frequently.
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What is secondary storage?
Any storage that isn't under the direct control of the CPU. It stores data and information when the computer is off.
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What is RAM?
Random acess memory. Is volatile, so all data is lost once the power supply is switched off. Stores programs and data currently in use. Can be written to and read from.
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What is ROM?
Read only memory. Stores programs needed to boot up the computer. Can only be read from. Non-volatile. Generally smaller in memory capacity.
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Magnetic
Magnetic storage uses magnets to record data on rotating metal plates. The most common example is a hard drive.
Advantages: 1. Large storage capacity 2. Decent read/write access 3. Cheap Disadvantages: 1. Moving parts result in wear and tear 2. Data can be lost/altered by magnets |
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Optical
Optical storage uses a lens and a light beam to read and write data onto a disk (e.g. CD, DVD).
Advantages: 1. Light and portable 2. Cheap 3. Durable 4. Some formats (e.g. CD-R) mean that data cannot be overwritten Disadvantages: 1. Small storage capacity 2. Specific drive needed to read/write data to/from the disk |
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Solid State
Solid-state uses flash memories/electrical circuits to store data. It is commonly used in USBs and SD cards.
Advantages: 1. Very quick read/write speed 2. Compact 3. No moving parts 3. Robust Disadvantages: 1. Expensive 2. Limited number of times that data can be written to |
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Cloud
Data is stored (using normal magnetic/solid state storage) at a remote location and is accessed via the Internet. Popular examples are Google Drive and Dropbox.
Advantages: 1. Can be accessed from anywhere in the world, granting increased flexibility 2. Can be accessed by multiple users at once 3. Users don't need to buy additional hardware Disadvantages: 1. Requires an Internet connection 2. No control over the data in terms of security |
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Clock Speed (Hz)
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Dictates the number of fetch-decode-execute cycles run per second.
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Number of Processor Cores
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Having multiple cores allows a CPU to process multiple instructions simultaneously.
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Cache Size
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Allows the CPU to store more instructions/data that are regularly used, reducing the time taken to process an instruction.
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Cache Type
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L1 cache is faster than L2 and L3 cache.
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Cheatography n. The art of mapping complex subjects into clear, instantly navigable reference guides.
