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System Unit

a case that contains electronic components of the computer used to process data; are available in a variety of shapes and sizes; made of metal or plastic and protects the internal electronic components from damage


sometimes called a system board; the main circuit board of the system unit


also called CPU or central processing unit; electronic component on a computer's motherboard that interprets and carries out the basic instructions that operate the computer; can contain a control unit and an ALU; impacts overall computing power and manages most of a computer's operations; the leading manufacturers of personal computer chips are Intel and AMD

CPU (Central Processing Unit)

electronic component on a computer's motherboard that interprets and carries out the basic instructions that operate the computer; also called processor.


some computer and chip manufacturers use this to refer to a personal computer processor chip

Multi-core processor

a chip with two or more separate processor cores; typically increase overall performance; more energy efficient that separate multiple processors

Dual-core processor

a chip that contains two separate processor cores

Quad-core processor

a chip with four separate processor cores

Control unit

the component of the processor that directs and coordinates most of the operations in the computer; it interprets each instruction issued by a program and then initiates the appropriate action to carry out the instruction

ALU (Arithmetic Logic Unit)

another component of the processor; performs arithmetic, comparison, and other operations

Machine cycle

operates four basic instructions/(1) fetching (2) decoding (3) executing (4) storing

Clock speed

the pace of the system clock is measured by the number of ticks per second; the faster it goes the more instructions the processor can execute per second

System clock

the processor relies on a small quartz crystal circuit to control the timing of all computer operations


recognize resent two discrete states: on (1) and off (0); most computers are this

Binary system

a number system that has just two unique digits-0 and 1; the computer uses this because it recognizes only two states

Bit (short for binary digit)

it is the smallest unit of data the computer can process; it's not very informative by itself


consists of electronic components that store instructions waiting to be executed by the processor, data needed by those instructions, and the results of processing the data; usually consists of one or more chips on the motherboard or some other circuit board in the computer; stores 3 basic categories of items-1)the operating system and other system software that control or maintain the computer and its devices 2)app programs that carry out a specific task such as word processing and its device 3)the data being processed by the app programs and resulting information

RAM (random access memory)

also called main memory; consists of memory chips that can be read and written to by the processor and other devices; files remain in here as long as the computer has continuous power; most is volatile; can hold multiple programs simultaneously

MB (megabyte)

is approximately 1 million bytes; is exactly 1,048,574 bytes; approximately 500 pages of text

GB (gigabyte)

approximately 1 billion bytes; exactly 1,073,741,824 bytes; approximately 500,000 pages of text

TB (terabyte)

is approximately 1 trillion bytes; exactly 1,099,511,627,776 bytes; approximately 500,000,000 pages of text

Volatile memory

is temporary; it loses its memory when the computer's power is turned off; ex:RAM

Nonvolatile memory

is permanent; doesn't lose its content when power is removed from the computer; ex:ROM, flash drive, CMOS

Memory slot

hold memory modules on the motherboard

Memory module

RAM chips usually reside on this; is a small circuit board


speeds up processing time because it stores frequently used instructions and data; if the instruction or data isn't found in memory, then it must search a slower speed storage medium such as a hard disk or optical disc; it searches memory in this order-L1 cache then L2 cache then RAM

L1 cache

is built directly in the processor chip; usually has a very small capacity, ranging from 8 KB to 128 KB

L2 cache

is slightly slower then L1 cache but has a much larger capacity, ranging from 64 KB to 16 MB

ROM (read-only memory)

refers to the memory chips storing permanent data and instructions; data on this can't be modified; is nonvolatile; often record data, instructions, or information on the chips when they manufacture the chips

Flash Memory

a type of nonvolatile memory that can be erased electronically and rewritten; most computers use this to hold their startup instructions because it allows the computer to easily to update its contents; store data and programs on many mobile computers and devices; flash memory cards contain this on a removable device instead of a chip


provides high speeds and consumes little power; uses battery power to retain information even when the power to the computer is off; batter-backed memory chips can keep the calendar, date, and time current even when the computer is off; flash memory chips that store a computer's startup information often use this

Access time

is the amount of time it takes the processor to read data, instruction, and information from memory; directly affects how fast the computer processes data


extremely fast; is one billionth of a second

Expansion slot

socket on the motherboard that can hold the adapter card

Expansion card

also called an adapter card; is a circuit board that enhances functions of a component of the system unit and/or provides connections to peripherals

Adapter card

also called an expansion card; circuit board that enhances functions of a component of a system unit and/or provides connections to peripherals


a device that connects to the system unit and is controlled by the processor in the computer; ex:modems, desk drives, printers, scanners, and keyboards

Sound card

enhances the sound-generating capabilities of a personal computer by allowing sound to be input through a microphone and output through external speakers or headphones

Graphics card

also called a video card; converts computer output into a video signal that travels through a cable to a monitor which displays an image in the screen

Video card

also called a graphics card; converts computer output into a video signal that travels through a cable to the monitor which displays an image on the screen

Memory card

a removable flash memory device, usually no bigger than 1.5" in height or width, that you insert and remove from a slot in a personal computer, game console, mobile device, or a card reader/writer

USB flash drive

a flash memory storage device that plugs in a USB port on a computer or mobile device

ExpressCard slot

is a special type of expansion slot that holds a PC card or an ExpressCard module; most netbooks don't have one

PC Card

is a thin, credit card-sized removable flash memory device that primarily is used today to enable traditional notebook computers and Tablet PCs to access the Internet wirelessly

ExpressCard module

can be used as a removable flash memory device; is about 1/2 the size of a PC Card and adds memory, communications, multimedia, and security capabilities to computers


is the point at which a peripheral attaches to or communicates with a system unit so that the peripheral can send data to or receive info from the computer; a keyboard, monitor, printer, mouse, and microphone attach to a port on the system unit

USB port (short for universal serial bus port)

can connect up to 127 different peripherals together with a single connector

Firewire port

similar to a USB port in that it can connect multiple types of devices that require faster data transmission speeds; allows you to connect up to 63 devices together


uses radio waves to transmit data between two devices; devices have to be within about 33 feet of each other

Docking station

is an external device that attaches to a mobile computer or device; contains a power connection and provides connections to peripherals


each channel allows the various devices both inside and attaches to the system unit to communicate with each other; are used to transfer bits from input devices to memory, to the processor, from the processor to memory, and from memory to output or storage devices


an opening inside the system unit in which you can install additional equipment; is different from a slot on the motherboard which is used for the installation of adapter cards

Expansion bus

allows the processor to communicate with peripherals

Front side bus

also called the system bus; is part of the motherboard and connects the processor to main memory

System bus

also called the front side bus; referring to this when computer professionals use the term bus by itself

Power supply

is the component of the system unit that converts the wall outlet AC power into DC power

Drive bay

a rectangular opening that typically holds disk drives

What is a bit and how does a series of bits represent data?

the smallest unit of data the computer can process; they form a byte when 8 bits are grouped together as a unit

How do program instructions transfer in and out of memory?


What are the characteristics of various personal CPUs and how are CPUs cooled?


Explain five things that you can do to care for the hardware of your system.


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