Cheat Sheet

(Most Know Terms and Information)

Server – manages network resources; software access; centralized storage

Network computers – typically rely on network for storage; no hard drive or CD

Minicomputer – up to 4,000 users connected via dumb terminals; can also act as server

Supercomputer - 64 billion instructions/second

Hyperlink (link) – built in connection to other related web pages.

Uniform Resource Locator (URL) – web page unique address. Consists of protocol, domain name, and sometimes path to specific web page

http:// - (hypertext transfer protocol) – communications standard used to transfer pages on the web

Search engine – software program used to find web sites, web pages, and Internet files.

Control Unit – directs & coordinates most of the operations in a computer

ALU – Arithmetic/Logic Unit – performs the execution part of the machine cycle; i.e., arithmetic, logic, comparison operations.

Machine Cycle – Fetch (obtain instruction or data), decode (translate the instruction into computer language, execute (carrying out the commands), storing (writing results to memory).

Clock speed – the speed at which processors execute instructions, measured in MHz (megahertz) – one million ticks of system clock, or GHz (gigahertz) – one billion ticks.

Zero Insertion Force (ZIF) socket – small lever or screw designed to facilitate the installation and removal of processor chips.

Analog – continuous signal to represent data; Digital – signal on or off

Binary – computer numbering system that only uses digits 0 and 1. 1=On, 2=Off. Each on/off digit value is called a bit. Eight bits = byte.

Volatile/Non-Volatile memory – volatile: contents of memory are lost when computer is turned off; non-volatile: not lost when powered off

SIMM and DIMM – Single Inline Memory Module – pins on opposite side of circuit board are connected; Dual Inline Memory Module – pins on opposite side of circuit board are NOT connected.

Cache – stores frequently used instructions and data. Level 1 (primary cache) built directly into processor chip. Level 2 (external cache) consists of high-speed SRAM chips.

CMOS – Complementary Metaloxide Semiconductor memory stores configuration data about computer (hard drive, monitor, and keyboard types, data and time stamps, and other startup information required to start computer). Uses battery power.

Universal Serial Bus (USB) - can connect up to 127 different peripheral devices to one connector. Devices are daisy-chained together outside the system unit.

SCSI ports - high-speed parallel ports; transfer up to 32 bits at once; daisy-chain up to 7 devices

IrDA ports – transmit data to system unit via infrared light waves.

Bitmap – rows and columns of dots, each dot consisting of data bits. Today’s scanners range 30-48 bits.

Pixel – single point in an electronic image

Printer control language (PCL) – standard printer language designed to support fonts and layouts.

Postscripts - commonly used in desktop publishing and graphic art – intense colors and graphics.

Track – narrow recording band that forms circle on surface of disk. 80 tracks on floppy;

Sector – pie-shaped sections of disk; 512 bytes of data; 18/track; Cluster – 2-8 sectors; smallest unit of space used to store data

File Allocation Table (FAT) – table used to locate files on disk.

Point of Presence (POP) – local phone # for net access

Packet – data broken into pieces when client computer sends data over Internet

Routers –used to send packets along fastest available path

TCP/IP (transmission control protocol/internet protocol) – communications protocol used to define packet switching on the Internet;

Tags - html codes that specify how text and other elements display in browser & where links lead

File Transfer Protocol (FTP) – Internet standard for file exchange

Cookies - track user preferences; shopping; site visits; targets advertising

Kernel – responsible for managing memory, files, devices, clock, starting applications, assigning resources.

Multiprocessing – can support 2 or more CPU’s running programs at same time.

Buffer – area of memory or storage where data is placed while waiting to be transferred to I/O device

Paging - swapping items between memory & storage

Thrashing - OS spends too much time paging instead of executing applications

Interrupt Request (IRQ) – communications line between device and CPU; most computers have 15

BIOS – Basic I/O System – firmware that contains computer’s startup instructions

Power-On Self Test POST – computer self-test to make sure hardware is connected & operating properly.

Registry – file used to store Windows system configuration information

Global Positioning System (GPS) – one or more earth-based receivers that accept and analyze signals sent by satellites in order to determine the receiver’s geographic location.

Internet – worldwide collection of networks that links together millions of business, government offices, educational institutions, and individuals via modems, telephone lines, satellites, and other communications devices and media.

Twisted-pair cable – consists of one or more twisted pair wires bundled together; each consisting of two separate insulated copper wires that are twisted together.

Coaxial cable – consists of a single copper wire surrounded by three layers: an insulting material, a woven or braided metal, and a plastic outer coating.

Fiber-Optic cable – consists of dozens or hundreds of thin strands of glass or plastic that use light to transmit signals.

Analog signal – consists of a continuous electrical wave.

Digital signal – individual electrical pulses that represent the bits grouped together into bytes.

Bandwidth – range of frequencies that a transmission medium can carry in a given period of time.

ISDN – set of standards for digital transmission of data over analog telephone lines. Provides faster transmission rates than regular telephone lines.

DSL – uses broadband to transmit a greater number of bytes on a standard twisted-pair cable.

Repeater – device that accepts a signal from a transmission medium, amplifies it, and retransmits it over the medium.

Bridge – device that connects two LANs using the same protocol, such as Enthernet.

Gateway – combination of hardware and software that connects networks that use different protocols.

Router – device that connects multiple networks, including those with differing protocols.

Ethernet – LAN protocol that allows personal computers to contend for access to the network.

Token-ring – controls access to the network by requiring that a special signal, called a token, is shared or passed among network devices.

Field – combination of one or more characters and is the smallest unit of data you can access.

Data type – specifies the type of data a field can contain: text, numeric, currency, date, memo, hyperlink, or object.

Record - group of related fields.

Validation – process of comparing data to a set of rules or values to determine if the data is accurate. Validity checks: alpha/numeric, completeness, range, consistency, check digit.

DBMS – software program or set of programs designed to control access to the database and manage the data resources efficiently.

Data dictionary – stores data about each file in the database.

Relational database – stores data in tables that consist of rows and columns.

Structured Query Language – used by relational databases to manipulate and retrieve data. Includes keywords and rules used to implement relational algebra operations: projection, selection, join operations.

Object – item that can contain both data and the activities that read or manipulate the data.

Object-oriented database - based on object-oriented data model and maintains objects.

Database administrator (DBA) – responsible for creating and maintaining data dictionary, establishing and monitoring security of database, monitoring database performance,, and implementing and testing backup and recovery procedures.

Database design guidelines – accurate, verifiable, timely, organized, meaningful and cost-effective information.

System Development Life Cycle (SDLC) – organized set of activities that guides those involved through the development of an information system. Five major phases: planning, analysis, design, implementation, support.

Gantt chart – bar chart that uses horizontal bars to represent project phases or activities.

Planning phase of SDLC – review project requests, prioritize them, allocate resources, identify project development team.

Analysis phase of SDLC – conduct preliminary investigation, perform detailed analysis consisting of study current system, determine users wants and needs, recommend solution.

Design phase of SDLC – acquire hardware and software, develop details of information system to be implemented.

Implementation phase – develop any necessary programs, install and test new system, train and education users, convert to new system.

Structured walk-through – step-by-step review of deliverables. Used throughout entire SDLC.

Program Development Life Cycle (PDLC) – set of steps that programmers use to build programs. Consists of six steps: analyze problems, design programs, code programs, test programs, formalize solutions, maintain programs.

Program specification package – detailed design specification that includes relationship among programs in a system as well as input, output, processing, and data requirements of each program.

Analyzing phase of PDLC – review program specifications, meet with systems analyst and users, identify each programs input, output and processing components.

Designing programs phase of PDLC – grouping each program’s activities into modules, devising a solution algorithm, or each module, and testing each solution algorithm.

Solution algorithm (or program logic) – graphical or written description of step-by-step procedures for a module.

Structure design – approach which all program logic is constructed from a combination of three control structures: sequence control structure, selection control structure, repetition control structure.

Design tools – help develop program solution algorithm: program flowcharts, Nassi-Schneiderman charts, pseudocode

Coding programs phase of PDLC – translating solution algorithm into programming language, entering programming language code into computer

Testing programs phase of PDLC – uncover syntax and logic errors by developing test data and debugging.

Formalize solution phase of PDLC – review program code, review documentation.

Maintaining programs phase of PDLC – correcting errors, adding enhancements.

Low-level language – written to run on one particular computer. Machine languages, assembly languages

High-level language - can run on many different types of computers. 3^rd-generation, 4^th-generation, natural languages.

Encapsulation – details of object are hidden from user

Class – objects may be part of a larger category of objects. Every object in a class shares similar methods and attributes.

Inheritance – concept of lower levels inheriting methods and attributes of higher levels

Script – interpreted program that runs on the client; i.e., runs on your computer as opposed to running on a Web server.

Applet – usually runs on the client but it is compiled.

Servlet – applet that runs on the server.

Multimedia Personal Computer – uses specific hardware and software to input, process, and output various types of media.

Developing multimedia applications – analysis, design, and production.

Multimedia authoring software – allows you to combine text, graphics, sound, animation, and video into an application.

Computer virus – segment of program code that implants itself into a computer file and spreads systematically from one file to another.

Boot sector virus – replaces the boot program used to start a computer with a modified infected version of the boot program.

File virus – attaches itself to or replaces program files then spreads to any file that accesses the infected program.

Trojan horse virus – hides within or is designed to look like a legitimate program.

Macro virus – uses the macro language of an applications to hide virus code.

Logic bomb – computer virus that activates when it detects a certain condition

Time bomb – type of logic bomb that activates on a particular date.

Polymorphic virus – modifies its program code each time it attaches itself to another program or file.

Stealth virus – can infect a program file but still report the size and creation date of the original uninfected program.

Biometric devices – authenticates a person requesting access by verifying personal characteristics such as fingerprints, hand size, signature, typing patterns, and retinal or voice patterns.

Encryption – process of converting readable data into unreadable characters to prevent unauthorized access.