Expo/Computation/The Metacomputer

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The Metacomputer: Glossary of Terms

Application

The type of job performed by a computer or system of computers. Examples of applications include: climate modelling; molecular dynamics; airline scheduling; word processing.

Algorithm

A set of rules or procedures by which a computer solves a problem in a stepwise fashion.

Architecture

A term used to describe the design of processors, both individual and in general. It may also be used to describe any complex system, eg. "software architecture", "network architecture".

Andrew File System (AFS)

A type of file system which is not dependent on any one computer to hold its files. With AFS, a user can login to any computer within the AFS environment and access his/her files, regardless of which computer actually stores the files. AFS is therefore a distributed file system.

Asynchronous Transfer Mode (ATM)

A networking medium which uses a fixed-size packet, called a cell, to transfer data. ATM can handle the "high bandwidth" requirements of multimedia data transmission (video and sound data use an extremely large amount of bits).

Bandwidth

Refers to how much data can be sent through a connection, usually measured in bits-per-second. The more bits-per-second, the "higher" the bandwidth.

Bit

The smallest bit of information in a binary encoding system, either a 1 or 0.

Bus

A common pathway that connects the parts of computer system and through which data in the form of electrical signals is transferred.

Byte

A unit of 8 contiguous binary digits, or bits. A byte represents one character.

C++

A superset of the C programming language. C++ was developed primarily to facilitate the management, programming, and maintenance of extremely large sets of C software. C++ is an object-oriented language; it manipulates data sets, or objects, rather than individual numbers.

Compiler

A program which reads a source program created by a programmer, and then converts the program into a set of instructions known as the object program, also known as machine code. The object program is in a form that a computer can underst and and execute directly.

Compile Server

A computer connected to a supercomputer, on which source programs for the supercomputer are compiled. This allows the supercomputer to use all of its resources for number crunching. The compile server's architecture matches the supercomputer's, so that the compiled object programs are compatible.

Debugging

Detecting, tracing, and eliminating mistakes in programs and other software.

Disk

A flat rotating disk covered on one or both sides with magnetizable material. Data is stored in concentric rings called "tracks" and read and written by a disk drive. There are two main types of disk: the hard disk and the floppy disk.

Domain Name

The unique identifier for a computer on the Internet. A domain name consists of a sequence of names separated by periods. As an example, "cm5.ncsa.uiuc.edu" is the domain name for the computer cm5 (the cm5 being referred to as the "hostname" corresponding to a Connection Machine 5) which is housed at NCSA at the University of Illinois at Urbana-Champaign (uiuc). Each sequence by itself may not be unique, but when put together is sufficient to assure a unique domain name.

Ethernet

A network system for local computers that uses a series of standard network protocols that allow different types of computers to communicate, at about 10,000,000 bits-per-second.

FDDI

Fiber Distributed Data Interface. A standard for transmitting data on optical fiber cables at a rate of around 100,000,000 bits-per-second (about 10 times faster than Ethernet).

File Transfer Protocol (FTP)

Allows the transfer of files between any machines supporting TCP/IP on a network. FTP provides a limited route by which a user can login to a computer for the sole purpose of retrieving and/or sending files.

Flop(s)

Floating point operations per second. A measure of how fast a computer is based on calculations per second. A floating point is a number representation consisting of a mantissa, an exponent, and an assumed radix. The number represented is M multiplied by R raised to the power of E (M*R^E) where R is the radix or base of the number system. (For example, 10 is the radix of the decimal system.)

Fortran

Fortran stands for FORmula TRANslator, the first and still the most widely used programming language for numerical and scientific applications. Popular versions include Fortran 77 and Fortran 90; some versions, such as HPF, have been developed to run on parallel processor machines.

Giga-

10^9 power. A gigabyte is 1,073,741,824 bytes, or roughly a billion bytes.

HiPPI

High Performance Parallel Interface. HIPPI is a simple point-to-point unidirectional connection for data transmission at speeds up to 800 Mbits/second on a single cable. HIPPI is normally (but not necessarily) deployed in pairs in order to achieve a full duplex connection (one that can allow simultaneous transmission in both directions).

HIPPI cables are limited to 25 meters by physical limitations, but repeaters can be used to connect cables together as well as extenders that work to extend HIPPI over fiber up to 20 kilometers. A HIPPI interface is commonly used to connect together a group of computers in close proximity, allowing very rapid transfers of data.

High-performance Fortran (HPF)

An extension of Fortran 90 which supports data parallel programming.

Interface

1) A network interface is the software that handles machine to machine communication.
2) A user interface refers to the aspects of a computer system or program which can be seen by the user, and the commands and mechanisms used to control a computer's operation and input data.

Load Balancing

Techniques which aim to spread tasks among the processors in a parallel processing system in order to avoid some processors standing idle while others have tasks queueing for execution. Load balancing may be performed by (a) heavily loaded processors sending tasks to other processors; (b) idle processors requesting work from others; (c) some centralized task distribution mechanism; or (d) some combination of these options.

Mainframe

A large computer that can handle many tasks and multiple users at the same time.

Mega-

A million, in reference to computing. A megabyte is a million bytes or a thousand kilobytes.

Message Passing Interface (MPI)

A "translator" language that allows different types of computers or processors to communicate and share tasks. Think of MPI as "computer Esperanto."

Network Protocol

A formal description of message formats and rules that two or more computers must follow in order to communicate across a network.

Node
In networking terms, an individual computer within a network that can communicate with other computers in the network. Also, refers to an individual processor within a multiprocessor machine which can communicate with other processors within that machine.

Object-oriented (Programming)

An method of programming that depends on sets of data objects, each capable of responding to a group of commands targeted at it.

Operating System
An integrated collection of programs that controls the execution of computer programs and performs system functions. Examples include VMS, DOS, UNIX, DOS, O/S 2, etc.

Packet

A unit of data sent across a network is referred to as a packet. Apart from data, each packet possesses routing and error-control information.

Parallelizing Code

The process of dividing the overall problem into separate tasks and allocating tasks to processors. This may be handled implicitly by the operating system, or explicitly by the programmer, where the programmer must annotate his program to show how it is to be partitioned.

Parallel Processing

The simultaneous use of more than one computer or processor to solve a problem. The processors may communicate in order to be able to cooperate in solving a problem or they may run completely independently, possibly under the control of another processor which distributes work to the others and collects results from them.

Peta-

10^15 power. A petaflop is a thousand trillion floating point operations per second, or a thousand teraflops.

Processor

A system or device that can carry out operations on data.

Round Robin (DNS)

A load balancing technique, where a group of computers take turns using a single domain name.

Scalable

A program designed on a workstation and can also be run on a larger machine (such as a supercomputer) is said to be scalable. Also, a computer to which more processors, disk drives, etc. can be added is referred to as scalable.

Shared Memory

Memory in a parallel computer, usually RAM (Random Access Memory - the "working memory" of the computer) which can be accessed by more than one processor, usually via a shared bus or network.

Software

Instructions or sets of instructions, also called a program, that directs a computer's handling of data.

Transmission Control Protocol/Internet Protocol (TCP/ICP)

Each term refers to a standard for software to control communications between computers on interconnected networks, particularly the Internet. A protocol is a set of rules controlling how computers communicate with eachother.

Transparency

1) Networking protocols are said to be transparent when not perceived in using a remote computer; instead, the user's perception is that of being directly linked to the remote computer, as if it's an integral part of his or her own computer.
2) In the context of "metacomputing," computers and other types of equipment may be separated by thousands of miles, yet they appear to the user interface as one system. This type of transparency depends heavily on very fast networks to prevent any time lag.

Tera-

In computing, a trillion. A terabyte is one trillion bytes.

Vector Processing

Calculations are performed in linear, assembly line fashion. Each processor carries out a mathematical step on a piece of data before handing the data off to the next processor.

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NCSA. Last modified, 10/21/95