COMPUTER SCIENCE - VOCABULARY - QUARTER 1 - WEEK 3
Hardware - The physical, touchable, material parts of a computer or other system. The term is used to distinguish these fixed parts of a system from the more changeable software or data components which it executes, stores, or carries. Computer hardware typically consists chiefly of electronic devices (CPU, memory, display) with some electromechanical parts (keyboard, printer, disk drives, tape drives, loudspeakers) for input, output, and storage, though completely non-electronic (mechanical, electromechanical, hydraulic, biological) computers have also been conceived of and built.
Motherboard - The main printed circuit board in an electronic device, particularly a computer, which contains sockets that accept additional boards ("daughter-boards"). In a (personal) computer, the motherboard contains the bus, the microprocessor and chips used for controlling any built-in peripherals such as the keyboard, text and graphics display, serial ports and parallel ports, joystick and mouse interfaces.
BIOS – (Basic Input/Output System) The part of the operating system of the IBM PC and compatibles that provides the lowest level interface to peripheral devices and controls the first stage of the bootstrap process. The BIOS is stored in ROM, or equivalent, in every PC. In order to provide acceptable performance (e.g. for screen display), software vendors directly access the routines in the BIOS, rather than using the higher level operating system calls. Thus, the BIOS in the compatible computer must be 100% compatible with the IBM BIOS. As if that wasn't bad enough, many application programs bypass even the BIOS and address the screen hardware directly just as the BIOS does. Consequently, register level compatibility is required in the compatible's display electronics, which means that it must provide the same storage locations and identification as the original IBM hardware.
Processor – (Central Processing Unit or CPU) The part of a computer which controls all the other parts. The CPU fetches instructions from memory and decodes them. This may cause it to transfer data to or from memory or to activate peripherals to perform input or output. A parallel computer has several CPUs which may share other resources such as memory and peripherals. The CPU Info Center lists many kinds of CPU.
ROM – (Read-Only Memory) A type of data storage device which is manufactured with fixed contents. In its most general sense, the term might be used for any storage system whose contents cannot be altered, such as a gramophone record or a printed book; however, the term is most often applied to semiconductor integrated circuit memories, of which there are several types, and CD-ROM. ROM is inherently non-volatile storage - it retains its contents even when the power is switched off, in contrast to RAM. ROM is often used to hold programs for embedded systems since these usually have a fixed purpose. ROM is also used for storage of the lowest level bootstrap software (firmware) in a computer.
RAM – (Random Access Memory Previously "direct-access memory"). A data storage device for which the order of access to different locations does not affect the speed of access. This is in contrast to, say, a magnetic disk, magnetic tape or a mercury delay line where it is very much quicker to access data sequentially because accessing a non-sequential location requires physical movement of the storage medium rather than just electronic switching. The most common form of RAM in use today is built from semiconductor integrated circuits, which can be either static (SRAM) or dynamic (DRAM). In the 1970s magnetic core memory was used. RAM is still referred to as core by some old-timers. The term "RAM" has gained the additional meaning of read-write. Most kinds of semiconductor read-only memory (ROM) are actually "random access" in the above sense but are never referred to as RAM. Furthermore, memory referred to as RAM can usually be read and written equally quickly (approximately), in contrast to the various kinds of programmable read-only memory. Finally, RAM is usually volatile though non-volatile random-access memory is also used. Interestingly, some DRAM devices are not truly random access because various kinds of "page mode" or "column mode" mean that sequential access is faster than random access.
Clock - A processor's clock or one cycle thereof. The relative execution times of instructions on a computer are usually measured by number of clock cycles rather than seconds. One good reason for this is that clock rates for various models of the computer may increase as technology improves, and it is usually the relative times one is interested in when discussing the instruction set.
Bus - A set of conductors (wires, PCB tracks or connections in an integrated circuit) connecting the various functional units in a computer. There are busses both within the CPU and connecting it to external memory and peripheral devices. The width of the bus, i.e. the number of parallel connectors, determines the size in bits of the largest data item which it can carry. The bus width and the number of data items per second which it can transmit are one of the factors limiting a computer's performance. Most current microprocessors have 32-bit busses both internally and externally. Some processors have internal busses which are wider than their external busses (usually twice the width) since the width of the internal bus affects the speed of all operations and has less effect on the overall system cost than the width of the external bus.
Port - 1. <networking> A logical channel or channel endpoint in a communications system. The Transmission Control Protocol and User Datagram Protocol transport layer protocols used on Ethernet use port numbers to distinguish between (demultiplex) different logical channels on the same network interface on the same computer. Each application program has a unique port number associated with it, defined in /etc/services or the Network Information Service "services" database. Some protocols, e.g. telnet and HTTP (which is actually a special form of telnet) have default ports specified as above but can use other ports as well. 2. <operating system, programming> To translate software to run on a different system or the results of doing so. 3. <language> An imperative language descended from Zed from Waterloo Microsystems (now Hayes Canada) ca. 1979.
Serial port - A connector on a computer to which you can attach a serial line connected to peripherals which communicate using a serial (bit-stream) protocol. The most common type of serial port is a 25-pin D-type connector carrying RS-232 signals. Smaller connectors (e.g. 9-pin D-type) carrying a subset of RS-232 are often used on personal computers. The serial port is usually connected to an integrated circuit called a UART which handles the conversion between serial and parallel data. In the days before bit-mapped displays, and today on multi-user systems, the serial port was used to connect one or more terminals (teletypes or VDUs), printers, modems and other serial peripherals. Two computers connected together via their serial ports, possibly via modems, can communicate using a protocol such as UUCP or CU or SLIP.
Parallel port - An interface from a computer system where data is transferred in or out in parallel, that is, on more than one wire. A parallel port carries one bit on each wire thus multiplying the transfer rate obtainable over a single wire. There will usually be some control signals on the port as well to say when data is ready to be sent or received. The commonest kind of parallel port is a printer port, e.g. a Centronics port which transfers eight bits at a time. Disks are also connected via special parallel ports, e.g. SCSI or IDE.
Expansion slot - A connector in a computer into which an expansion card can be plugged. The connector supplies power to the card and connects it to the data bus, address bus and control signals of the motherboard.