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Glossary
Look up any term from this course. Each entry links back to the lesson that taught it.
| Term | Definition | Lesson |
|---|---|---|
| 3-2-1 backup rule | Keep three copies of data, on two types of media, with one copy off-site. | RAID and Backup |
| Accumulator (ACC) | Register holding the results of calculations done by the ALU. | The Microprocessor |
| Arithmetic logic unit (ALU) | The part of the CPU that performs arithmetic (add, subtract) and logical operations (AND, OR, NOT, comparisons). | The Microprocessor |
| Bus | A set of parallel wires (or tracks on a circuit board) that carries data, addresses or control signals between components of a computer. | Buses: Data, Address and Control |
| Cache | Small, very fast memory on the CPU that keeps copies of frequently used instructions and data. | The Microprocessor |
| Clock speed | The number of cycles a CPU performs per second, measured in gigahertz (GHz). | What Makes a Processor Faster |
| Control unit (CU) | The part of the CPU that fetches and decodes instructions and sends control signals to coordinate the ALU, registers, memory and input/output. | The Microprocessor |
| Core | An independent processing unit within a CPU. Multi-core CPUs can run several tasks at once. | What Makes a Processor Faster |
| Current instruction register (CIR) | Register holding the instruction currently being decoded and executed. | The Microprocessor |
| ECC memory | Error-correcting RAM that detects and fixes small memory errors; used in servers. | Memory: RAM, ROM and Cache |
| Fetch–decode–execute cycle | The repeated process by which the CPU fetches an instruction from memory, decodes it and carries it out. | The Fetch–Decode–Execute Cycle |
| Hard disk drive (HDD) | Magnetic storage on spinning platters; large capacity at low cost, but slower and less robust than an SSD. | Backing Storage |
| Hot-swappable | Able to be replaced while the system is running. | Server Hardware |
| Memory address register (MAR) | Register holding the address of the memory location about to be read or written. | The Microprocessor |
| Memory data register (MDR) | Register holding the data or instruction just read from, or about to be written to, memory. | The Microprocessor |
| Motherboard | The main printed circuit board in a computer. It holds the CPU socket, memory slots, chipset and connectors, and carries power and data between all the components. | The Motherboard |
| Parity | Extra data calculated from the other blocks in a stripe (using XOR) so that any single missing block can be rebuilt. | RAID and Backup |
| Peripheral | A device connected to the system unit that adds input, output or storage, but is not part of the core CPU and memory. | Input Devices |
| Pipelining | Overlapping the fetch, decode and execute stages of different instructions so the CPU is never idle. | What Makes a Processor Faster |
| Port | A socket on a computer where a cable from a peripheral or network connects, following a standard that defines the shape, signals and speed. | Ports and Connectors |
| Program counter (PC) | Register holding the address of the next instruction to fetch. | The Microprocessor |
| RAID | Redundant Array of Independent Disks: several physical drives combined so the system sees them as one, to improve speed, protect against drive failure, or both. | RAID and Backup |
| RAM (random access memory) | Volatile main memory that holds the operating system, the programs that are running and the data they are using. Its contents are lost when the power is switched off. | Memory: RAM, ROM and Cache |
| Redundancy | Having spare, duplicate components so the system keeps working when one of them fails. | Server Hardware |
| ROM (read-only memory) | Non-volatile memory whose contents are kept without power and are normally not changed during use. It stores firmware such as the start-up program. | Memory: RAM, ROM and Cache |
| Solid-state drive (SSD) | Storage using flash memory chips, with no moving parts. NVMe SSDs connect over PCIe and are the fastest common type. | Backing Storage |
| UPS (uninterruptible power supply) | A device containing batteries that instantly supplies power to connected equipment when the mains fails, and filters surges and dips. | Server Hardware |
| Virtual memory | Part of the storage drive used as extra memory when RAM is full; much slower than RAM. | Memory: RAM, ROM and Cache |
More lessons in Computer Hardware and Peripherals · Previous: Course Exam