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Terminology

 

Boot
The process that takes place when a PC is turned on and performs the routines necessary to get all the components functioning properly and then loads the operating system.
Bus
Millions of bits of information are constantly flashing among the components of the PC even when it appears to be simply sitting there. The bus is the highway system for all this data. The bus transports data among the processor and other components. There is no single component you can point to and say that this is the bus. The bus is a complex conglomeration of electrical circuits that permeate the PC. Bus speed is measured in bits - typically either 16 or 32. This is the size of the word that can be moved along the path.
CD ROM Drive
Uses a laser beam to read data from a spiral of indentations and flat areas on a layer of a compact disc, similar to musical compact discs.
CD ROM-DVD Drive
Similar to CD ROM Drive except that the data is more compact and stored on more than one layer of the disc giving it a storage capacity much larger.
Circuit Board
Most of the components of a computer are mounted on a circuit board of which the motherboard is the largest. Expansion cards and memory chips plug into the motherboard ganged together on small circuit boards to create single in-line memory modules or SIMMS.
Clock
A microchip that regulates the timing and speed of all the computers functions. The chip includes a crystal that vibrates at a certain frequency when electricity is applied to it. The shortest length of time in which a computer can perform some operation is one vibration of the clock chip. The speed of clocks, and therefore computers, is expressed in megahertz.
CMOS
Stands for Complementary Metal Oxide Semiconductor. The CMOS, powered by a small battery, chip retains crucial information about what hardware a PC comprises even when power is turned off.
CPU
Stands for Central Processing Unit. This is a microchip that processes information and the code instructions used by the computer. It is the brains of the computer. It consists of a controller (traffic cop), registers (computers fastest memory), and the arithmetic logic unit or ALU. The ALU is the number cruncher.
Daughterboard
See motherboard below.
Floppy Drive
Name come from the past when the discs could be easily bent. It takes a 3.5 inch disc that contains 1.44 MB of data.
 
Hard Drive
A mechanism in a computer used to store data. Before it is processed, it is moved to main memory and then to the registers of the CPU as needed. This memory is slower than RAM  but it remains when the PC is turned off. It consists of spinning disk (s) in the computer that is accessed with read-write heads. The capacity of a hard drive is usually measured in megabytes or gigabytes. As of this writing, the minimum on new computers is around 20 gigabytes.
A sealed metal housing protects the components A cutaway showing the major components inside the metal housing is also shown here.
A printed circuit board is located at the bottom of the drive. This board, also known as a logic board, receives commands from the drive's controller, which in turn is controlled by the operating system. The logic board translates those commands into voltage fluctuations that force the head actuator to move the read/write heads across the platters' surfaces.
A spindle connected to an electrical motor spins as many as eight magnetically coated platters at several thousand rotations per minute. The number of platters and the composition of the magnetic material coating them determines the capacity of the drive.
Read/write heads, attached to the ends of the moving arms, move in unison across the surface of the hard drive's spinning platters. The heads write the data coming from the disk controller to the platters by aligning magnetic particles on the surface of the platters. The heads read data by detecting the polarities of particles that have already been aligned.
The system keeps track of where data is stored by consulting and writing to a file allocation table or FAT. A single file may be stored in many non-contiguous locations.
IDE Controllers
A computer usually has two IDE slots built into the motherboard. They provide connections for ribbon cables that send signals controlling the floppy drive, hard drive, and CD-ROM drives.
Interrupts
Some hardware events, such as a keystroke, coming through a serial or parallel port need an immediate response from the processor. These are handled by a signal called an interrupt. They cause the operating system to temporarily stop what it is doing and divert its attention to the service required by the interrupt signal.
Keyboard
The processor continuously scans for signals being sent from the keys. The signal is generated when the user presses a key an a circuit is closed as shown here in a cut away depiction of the base of a key.
Depending upon the key being pressed, the processor interprets the signal as one of the recognizable numbers, symbols, or characters that is within its vocabulary. The representation is contained a an internationally recognized table called the American Standard Code for Information Interchange or ASCII table or code.                                                             
Microprocessor
The brains of the computer. It is a tight, complex collection of transistors arranged so that they can be used to manipulate data. Most computer operations are handled by the processor and the design of the processor dictates how software must be written to work correctly with the computer.
Modem
Stands for Modulate Demodulate. It converts the digital information of the computer to analog information required by most phone lines. It is used to connect to the Internet, for example.
Monitor
The screen is controlled by a video adapter and displays the contents of special video memory in the adapter, typically called VRAM. VRAM is addressable by the CPU and may contain codes, colors and attributes of characters, or colors and intensities of individual pixels (picture elements) when running in graphics mode.
Digital signals from the operating environment or application software are received by the variable graphics array (VGA) adapter. The adapter runs the signals through a digital to analog converter or DAC. Usually, three DACS are included, one of each of the primary colors (red, green, and blue). The DAC compares the signal to those in a look up table that contains the matching voltage levels for the three primary colors.
The adapter then sends signals to three electron guns located in the back of the monitor's cathode ray tube or CRT that focuses and aims the electron beams.
The beams pass through holes in a metal plate called a shadow mask. The purpose of this mask is to keep the beams precisely aligned with their targets on the CRT screen. The CRT's dot pitch is the measurement of how close the holes are to each other. A smaller dot pitch means the holes are closer to each other. This in turn means a sharper image.
The electrons strike the phosphors coating the inside of the screen. The phosphors are materials that glow when struck by electrons. Three different phosphors are used - one sensitive to each of the three primary colors mentioned above. To create different colors, the intensity of each of the three colors is varied. After a beam leaves a phosphor dot, the phosphor continues to glow briefly. This condition is called persistence. In order for an image to remain stable, the phosphors must be reactivated by repeated scans of the electron beams.
Motherboard
This is a sheet of plastic onto which metallic circuits have been printed and to which slots for other components wait to receive daughter boards, smaller circuit boards that add to the motherboard capabilities
Operating System
This software exists to control the operations of hardware. Essentially, the operating system directs any operation, such as writing data to memory or to disk, and regulates the use of hardware among several application programs that are running at the same time. This frees program developers from having to write their own code for these most basic operations. Examples are Windows 3.1, 95, 98, Me, 2000, NT, and XP
OCX Controls
Short for OLE custom control. It is a software module based on OLE and COM technologies that, when called by an application, produces a control that adds some desired feature to the application. OCX technology is portable across platforms, works on both 16-bit and 32-bit operating systems, and can be used with many applications. It is the successor to VBX (Visual Basic Custom Control) which supported only Visual Basic applications. OCXs have been superseded by ActiveX controls, which are much smaller and therefore work much better over the Internet.
Parallel Port
The parallel port is most often used to connect a printer which requires a high throughput of data.
PCI Expansion Slot
Stands for Peripheral Component Interconnect. They are designed for cards that use Plug and Play, a hardware design that lets the cards adapt to the PC automatically.
RAM
Stands for Random Access Memory. This is memory or disks that can be both read and written to. Random  access memory is really a misnomer because even ROM can be accessed randomly. The term originally applied to tape storage devices.
Reading from RAM
When software wants to read data stored in RAM, another electrical pulse is sent along the address line, once again closing the transistors connected to it. Everywhere along the address line where there is a capacitor holding a charge, the capacitor will discharge through the circuit created by the closed transistors, sending electrical pulses along the data lines. The software recognizes which data lines the pulses come from and interprets each pulse as a 1, and any line along which a pulse is not sent as a 0.
ROM
Stand for Read Only Memory. These are memory chips or data stored on disks that can be read by the computer's processor. The PC cannot write new data to RAM chips or disk drives.  The term originally was used to distinguish RAM from data and software that was stored on magnetic tape, and which could be accessed only sequentially.
Sound Card
Contains the circuitry for recording and reproducing multimedia sound.
ROM BIOS
Stands for Read Only Memory Basic Input Output System. A collection of software codes built into a PC that handle some of the fundamental tasks of sending data from one part of the computer to another.
Serial Ports
Most PCs have two serial ports. They are used for devices that do not require high data transfer such as a mouse. Those that require high data transfer, such a printers, are usually connected to the parallel port.
SIMMS
See circuit boards above.
System Files
Small disk files that contain software code that are the first files a computer reads from disk when it is booted.
Transistor
Electrical device that has two states - open or closed. It is therefore ideally suited for the binary system and many millions are used in the PC to store data.
USB Ports
Stands for Universal Serial Bus. They are a solution to the PC's lack of interrupts and other system resources to let software connect directly to peripherals. USBs can connect keyboards, mice, monitors, printers, and other devices without encountering resource conflicts.
Video Card
Translates image information into the varying electrical currents needed to display an image on the monitor.
Software, in coordination with the operating system, sends a burst of electricity along an address line which is a microscopic strand of electrically conductive material etched into a RAM chip. This burst identifies where to record data along the many address lines in the chip. At each memory location in the chip where data can be stored, the pulse turns on or closes a transistor that is connected to a data line. While the transistors are turned on, the software sends bursts of electricity along selected data lines.
When the electrical pulse reaches an address along which a transistor has been turned on, the pulse flows through the closed transistor and charges a capacitor. The process repeats itself continuously to refresh the capacitor's charge, which would otherwise slowly leak out. When the computer is turned off, the capacitors lose their charges. Each charged capacitor along the address line represents a 1 bit. An uncharged capacitor represents a 0 bit.