Computing Terms by Dan, M1ETN

Basic Computer Terms you may come across.

Glossary of Computing terms

In the descriptions, there are words or abbreviations used, that may not be understood, if it is underlined, and in blue, please click it to find out what that abbreviation means.

PC - Personal Computer.

Hardware - The physical bits of a PC system, yes a mains lead can be classified as "Hardware"

Software - This is all the programs you put on the computer, below are a couple of examples

Operating System (OS) - this is the program (Software) which controls the how the computer does what you tell it to do.

Windows - This is the operating system used by most PCs. It gives you and easy to use interface, which is graphical in its use.

DOS - Disk Operating System, this came out before Windows, and was very good at the time, unfortunately this system did not use a GUI, so was very hard to use.

LINUX - This is a UNIX clone developed by a German bloke called Linus Torvalds, with the assistance of developers around the world. This is the operating System that is running the GB3LV IRLP box. More information can be found here.

HUB - This is used when Networking 2 or more PCs together, when using CAT5 cable. Basically this is a bit of equipment that can be inserted in the cable run between PCs, to allow them to communicate. If you look at a network it may look like a bicycle wheel, with the Hub, being the center axle, and the cable run being the spokes, the PC being at the end of the spokes.

Network - This is a system by where 2 or more PCs can "talk" to each other, there are many different types of networking, with different protocols, and configurations. The most common used in the Home network, and small businesses is the 10baseT or 100baseTX, which use the Hub system mentioned above. The MAX speed of 10baseT is 10Mb, and for 100baseTX - 100Mb. There is another system which was used called 10base2, this was built using COAX (Rated at 50ohms), and the computers where daisy chained together. This was a simple system, but the speed was slower than the 10baseT networks.

BUS - This is what computer people call the physical connections between the cpu the memory, I/O (Input / Output) cards etc. See BUS TYPE below

Modem - This is what you use to connect to the internet. It stands for Modulator / Demodulator.

Internet - This is a global network of computers, with many uses, from the colorful World Wide Web, to basic data transfer.

CPU - This stands for Central Processing Unit. Basically this is you Pentium / 486 / 386 / 286 etc chip. Note this is not the PC system as a whole it is *only* the chip that the system is based upon. There are many different types and makes, the two main ones are the Pentium from Intel, and the Athlon / Duron from AMD.

Protocols - These are the system or "code" the computer uses to communicate with the other computer. There are many protocols, and if you set one PC to use say TCP/IP (The most common used for networking), the other should have the same set-up. As there are so many different ones, and they each do different things, please E-mail me, catch me on the radio, or see me at a club meeting to ask me.

CAT5 - This is one type (The most common type) used in networking, all it is, is a cable made up of 4 pairs of cable, each pair is twisted together. The amount of twists per inch is how a network cable is measured. This ranges from Cat3 (Telephone Wire, max data rate 2M) to Cat6 (1Gb) Cat5 is rated at a max of 100M/byte. All data cable is rated at 120ohms.

GUI - Graphical User Interface. This is what most operating systems use, it is a very easy way to help you use the PC, as everything has a graphical representation.

NIC - Network Interface Card, another name for you Network card (10b2, 10bt, or 100bTX) depending on what sort of network you have.

RAM - Random Access Memory, this is volatile memory, once the power has been turned off, and information held in the chip will be lost. This is used in every computer to speed up programs. The Hard Drive loads the program to RAM, and then if you need it again in a short time, it will load faster.

FIFO - This is related to data streams, mainly in the operation configuration of RAM. FIFO stands for First In First Out, i.e. bit 1 goes in the the RAM 1st, and bit 1 comes out 1st.

FILO - This is First In Last Out, i.e. bit 1 goes in 1st, but come out last.

Some terms you may have heard me talk about, mainly to do with my job.

PCM - Pulse Code Modulation. A method by which an audio signal is represented as digital data. Virtually all digital audio systems use PCM, including, CD, DAT, F1 format, 1630 format, DASH, DCC, and MD. Many people get confused because "PCM" is also slang for Sony's F1 format which stores PCM digital audio on videotape.

MUX - Multiplexing 1. <communications> (Or "multiple access") Combining several signals for transmission on some shared medium (e.g. a telephone wire). The signals are combined at the transmitter by a multiplexor (a "mux") and split up at the receiver by a demultiplexor. The communications channel may be shared between the independent signals in one of several different ways: time division multiplexing, frequency division multiplexing, or code division multiplexing. If the inputs take turns to use the output channel (time division multiplexing) then the output bandwidth need be no greater than the maximum bandwidth of any input. If many inputs may be active simultaneously then the output bandwidth must be at least as great as the total bandwidth of all simultaneously active inputs. In this case the multiplexor is also known as a concentrator.

2. <storage> Writing multiple logical copies of data files. Placing the copies on totally separate paths to mirrored devices greatly reduces the probability of all copies being corrupt. Multiplexing differs from mirroring in that mirroring takes one data file and copies it to many devices, thus making it possible to copy a corrupt file many times. Multiplexing writes the data files to many places simultaneously; there is no "original" data file.

TDM - Time Division Multiplexing. A type of multiplexing where two or more channels of information are transmitted over the same link by allocating a different time interval ("slot" or "slice") for the transmission of each channel. I.e. the channels take turns to use the link. Some kind of periodic synchronising signal.

WDM - Wave Division Multiplexing. A form of frequency division multiplexing specifically for packing many Optical Carrier n signals into a single optical fibre. The technique relies on the fact that a laser can be designed to emit monochromatic light. Each signal to be transmitted is attached to a laser that emits a different colour light beam, all the light beams are sent at the same time and a receiving device splits the colours into the original signals again. The device that joins the signals together is known as a multiplexor, and the one that splits them apart is a demultiplexor. With the right type of fibre you can have a device that does both and that ought to be called a mudem but isn't. The first WDM systems combined two signals and appeared around 1985. Modern systems can handle up to 128 signals and can expand a basic 9.6G bps fibre system to a capacity of over 1000G bps. These systems are sometimes called dense wave division multiplexing or DWDM systems. DWDM systems are popular with telecommunications companies because they allow them to expand the capacity of their fibre networks without digging up the road again. All they have to do is to upgrade the DWDM cards at each end. However DWDM systems are expensive and complicated to run. There is currently no standard for DWDM kit which makes it awkward to integrate with older but more standard SONET systems. r distinguishing identifier is usually required so that the receiver can tell which channel is which.

DWDM - Dense Wave Division Multiplexing.

Below is some commonly used bus types found on computers

The links in the info below should take you to the internet dictionary for computing terms.

There main website is http://foldoc.doc.ic.ac.uk/foldoc/index.html

ISA - Intergrated Standard Architecture. A bus standard for IBM compatibles that extends the XT bus architecture to 16 bits. It also allows for bus mastering although only the first 16 MB of main memory is available for direct access. In reference to the XT bus architecture it is sometimes referred to as "AT bus architecture".

EISA - Extended Industry-Standard Architecure. A bus standard for IBM compatibles that extends the ISA bus architecture to 32 bits and allows more than one CPU to share the bus. The bus mastering support is also enhanced to provide access to 4 GB of memory. Unlike MCA, EISA can accept older XT bus architecture and ISA boards. EISA was announced in late 1988 by compatible vendors as a counter to IBM's MCA in its PS/2 series. Although somewhat inferior to the MCA it became much more popular due to the proprietary nature of MCA.

PCI - Peripheral Component Interconnect. A standard for connecting peripherals to a personal computer, designed by Intel and released around Autumn 1993. PCI is supported by most major manufacturers including Apple Computer. It is technically far superior to VESA's local bus. It runs at 20 - 33 MHz and carries 32 bits at a time over a 124-pin connector or 64 bits over a 188-pin connector. An address is sent in one cycle followed by one word of data (or several in burst mode). PCI is used in systems based on Pentium, Pentium Pro, AMD 5x86, AMD K5 and AMD K6 processors, in some DEC Alpha and PowerPC systems, and probably Cyrix 586 and Cyrix 686 systems. However, it is processor independent and so can work with other processor architectures as well. Technically, PCI is not a bus but a bridge or mezzanine. It includes buffers to decouple the CPU from relatively slow peripherals and allow them to operate asynchronously.

AGP - Accelerated Graphics Port A bus specification by Intel which gives low-cost 3D graphics cards faster access to main memory on personal computers than the usual PCI bus. AGP dynamically allocates the PC's normal RAM to store the screen image and to support texture mapping, z-buffering and alpha blending. Intel has built AGP into a chipset for its Pentium II microprocessor. AGP cards are slightly longer than a PCI card. AGP operates at 66 MHz, doubled to 133 MHz, compared with PCI's 33 Mhz. AGP allows for efficient use of frame buffer memory, thereby helping 2D graphics performance as well. There is now an AGP x4 spec, which is 266MHz. AGP provides a coherent memory management design which allows scattered data in system memory to be read in rapid bursts. AGP reduces the overall cost of creating high-end graphics subsystems by using existing system memory.

IDE - Intergrated Drive Electronics (ATA, Advanced Technology Attachment) A disk drive interface standard based on the IBM PC ISA 16-bit bus but also used on other personal computers. The ATA specification deals with the power and data signal interfaces between the motherboard and the integrated disk controller and drive. The ATA "bus" only supports two devices - master and slave. ATA drives may in fact use any physical interface the manufacturer desires, so long as an embedded translator is included with the proper ATA interface. ATA "controllers" are actually direct connections to the ISA bus. Originally called IDE, the ATA interface was invented by Compaq around 1986, and was developed with the help of Western Digital, Imprimis, and then-upstart Conner Peripherals. Efforts to standardise the interface started in 1988; the first draft appeared in March 1989, and a finished version was sent to ANSI group X3T10 (who named it "Advanced Technology Attachment" (ATA)) for ratification in November 1990. X3T10 later extended ATA to Advanced Technology Attachment Interface with Extensions (ATA-2), followed by ATA-3 and ATA-4.

SCSI - Small Computer System Interface. The most popular processor-independent standard, via a parallel bus, for system-level interfacing between a computer and intelligent devices including hard disks, floppy disks, CD-ROM, printers, scanners, and many more. SCSI can connect multiple devices to a single SCSI adaptor (or "host adaptor") on the computer's bus. SCSI transfers bits in parallel and can operate in either asynchronous or synchronous modes. The synchronous transfer rate is up to 5MB/s. There must be at least one target and one initiator on the SCSI bus. SCSI connections normally use "single ended" drivers as opposed to differential drivers. Single ended SCSI can suport up to six metres of cable. Differential ended SCSI can support up to 25 metres of cable. SCSI was developed by Shugart Associates, which later became Seagate. SCSI was originally called SASI for "Shugart Associates System Interface" before it became a standard. Due to SCSI's inherent protocol flexibility, large support infrastructure, continued speed increases and the acceptance of SCSI Expanders in applications it is expected to hold its market. The original standard is now called "SCSI-1" to distinguish it from SCSI-2 and SCSI-3 which include specifications of Wide SCSI (a 16-bit bus) and Fast SCSI (10 MB/s transfer). SCSI-1 has been standardised as ANSI X3.131-1986 and ISO/IEC 9316. A problem with SCSI is the large number of different connectors allowed. Nowadays the trend is towards a 68-pin miniature D-type or "high density" connector (HD68) for Wide SCSI and a 50-pin version of the same connector (HD50) for 8-bit SCSI (Type 1-4, pin pitch 1.27 mm x 2.45 mm). 50-pin ribbon cable connectors are also popular for internal wiring (Type 5, pin pitch 2.54 mm x 2.54 mm). Apple Computer used a 25-pin connector on the Macintosh computer but this connector causes problems with high-speed equipment. Original SCSI implementations were highly incompatible with each other. ASPI is a standard Microsoft Windows interface to SCSI devices.

ATAPI - AT Attachment Packet Interface. Part of the EIDE interface that provides additional commands to control a CD-ROM drive or magnetic tape.