Basic Concepts of Computer and Computer Storage

Vocabulary terms and definitions covering basic computer components, types of memory, and various storage technologies and characteristics.

Computer

A machine that receives input, stores and manipulates data, and provides output in a useful format.

Central Processing Unit (CPU)

The portion of a computer system that controls nearly all activities, carries out program instructions, and serves as the primary element for functions.

Microprocessor

A single computer chip on which the CPU resides in modern computers.

Arithmetic Logic Unit (ALU)

The sub-section of the CPU where actual math and logic operations are performed under the direction of the control unit.

Control Unit (CU)

The sub-section of the CPU that directs the arithmetic logic unit (ALU).

Memory (Main Memory)

The storage place for data directly accessed by the CPU, typically consisting of SIMMs mounted on the motherboard.

Random Access Memory (RAM)

Temporary memory used by the computer to store information while applications are in use; at least $64$ RAM is cited as a modern PC requirement.

Read-Only Memory (ROM)

Computer memory on which data has been prerecorded that cannot be removed and can only be read.

Storage (Hard Disk)

The computer's primary storage media device, consisting of a rigid circular disk located inside a hard disk drive.

Keyboard

The primary input device used to enter commands and data.

Scanners

Input devices that transfer pictures and photographs to a computer, sometimes using optical character recognition software to convert printed documents into text.

Output Devices

Computer hardware equipment used to communicate the results of data processing to the outside world.

Monitor

The primary output device used to display information on a screen, available in monochrome or full colors.

LCD (Liquid Crystal Display)

A lightweight screen type that consumes less power compared to traditional monitors; used by most modern computers.

Printer

A device that transfers information from the PC to various sizes of paper; basic types include dot matrix, inkjet, and laser.

Speaker

External computer hardware that often includes a low-power internal amplifier and disables the lower fidelity built-in speaker.

Computer Data Storage

Technology consisting of computer components and recording media used to retain digital data.

Primary Storage (Memory)

Storage directly accessible to the CPU where instructions are continuously read and executed and active data is stored.

Secondary Storage

Storage not directly accessible by the CPU, accessed via input/output channels; hard disks are a typical example.

Tertiary Storage

Storage involving robotic mechanisms to mount/dismount removable mass storage media; used for archival of rarely accessed information.

Offline Storage

Also known as disconnected storage, this medium is not under the control of a processing unit and requires a human operator to be connected.

Byte

A standard string length of eight $0$'s or $1$'s in a row; it equals one character.

Character

A letter, number, or symbol representing anything that can be typed on a keyboard; computers typically use $256$ standard characters.

Non-volatile memory

Memory or storage where data is saved regardless of whether power is on or off, such as hard drives and ROM.

Volatile memory

A type of storage, such as RAM, whose contents are erased when power is turned off or interrupted.

Sequential Access

A retrieval method where the device must move through all information up to a specific location to read or write data; typical of offline storage.

Random Access

The ability of a computer to locate and retrieve data from a storage device immediately, such as with a hard drive.

Mutable storage (Read/write storage)

Storage that allows information to be overwritten at any time.

Immutable storage

Storage that allows information to be written only once (Write Once Read Many) or retains info from manufacture; examples include CD-ROM and CD-R.

Dynamic Random Access Memory (DRAM)

Common RAM that stores info in cells containing capacitors and transistors that must be refreshed with electricity every few milliseconds.

Static Random Access Memory (SRAM)

Memory that requires a constant power flow; it is quicker than DRAM but more expensive, often used for cache and video cards.

Raw capacity

The total amount of stored information a storage device can hold, expressed in bits or bytes.

Memory storage density

The compactness of stored information, calculated as capacity divided by a unit of length, area, or volume.

Location-addressable storage

Storage where each unit of information is selected with its numerical memory address; usually limited to primary storage.

File addressable storage

Storage divided into variable length files selected with human-readable directory and file names; used in secondary and tertiary storage.

Content-addressable storage

Storage where information is selected based on its contents; hardware versions are often used in a CPU cache.

Floppy Disk

A thin, flexible magnetic storage medium invented by IBM in $1969$, available in $8\text{-inch}$, $5\frac{1}{4}\text{-inch}$, and $3\frac{1}{2}\text{-inch}$ sizes.

Compact Disk (CD)

An optical disk introduced in $1982$; a standard $120\text{mm}$ disk can hold up to $700\text{MB}$ of data.

Digital Versatile Disk (DVD)

An optical storage device that can store six times more data than a standard compact disk.

Blu-ray Disc (BD)

Optical disks manufactured by Sony used for gaming and HD video; they use blue-violet lasers and can store up to $50\text{GB}$.

Flash Memory

A non-volatile memory in computer technology that can be electrically programmed or erased.

USB Flash Drive

A memory storage device integrated with the Universal Serial Bus interface, with capacities ranging from $64\text{MB}$ up to $128\text{GB}$.

Punch Cards

Stiff paper pieces containing digital information represented by the presence or absence of perforated holes.