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CS110: Introduction to Computers

PC Architecture Terminology Guide - Fall 2002

Note: These items are intentionally not in alphabetical order. I’ve attempted to group related things together, for example the types of memory.

 

Computer

A device that accepts input, processes & stores data, and produces output.

CPU (Central processing unit)

The main processing unit in a computer, consisting of circuitry that executes instructions to process data. The key component in a microprocessor, such as the Intel Pentium. In general conversation, the terms CPU and microprocessor are used synonymously.

Memory

The computer circuitry that holds program instructions and data.

RAM (Random Access Memory)

A type of computer memory circuit that holds data, program instructions and the operating system while the computer is on. RAM holds raw data that is waiting to be processed, as well as the instructions that will process the raw data. In addition, RAM holds processed data before it is stored more permanently on disk.

 

Another attribute of RAM is that it is volatile. That is, when power to the chips, or system, is lost or turned off the contents of RAM memory are lost. That’s one of the reasons it seems to take so long to shut down your computer, because the Operating System is writing any important information, back out to disk.

ROM (Read-only Memory)

One or more integrated circuits (i.e. chips) that contain (semi-) permanent instructions that the computer uses during the boot process.

 

ROM is necessary because, when you turn on the computer, the CPU receives electrical power and is ready to begin executing instructions, but because the computer was just turned on, RAM is empty and does not have any instructions for the CPU to execute. This is where ROM comes into play; its ROM BIOS instruction set tells the computer how to access the disk drives, and other peripheral devices.

 

The instructions on some ROM chips are permanent, hence the only way to change them is to remove the ROM chips from the motherboard and replace them with another set. However, many computers utilize a type of programmable ROM, also called Flash Rom, that allow for the BIOS program instructions to be upgraded in place. (This is sometimes necessary on older computers when installing new technology, such as a new Operating System version or new peripherals, e.g. new rewriteable DVD or new disk drive technology.)

ROM BIOS (Basic Input/Output System)

A small set of basic input/output system instructions stored in ROM, which cause the computer system to load critical operating files when the user turns on the computer, and tell the computer how to access the disk drives and other peripheral devices (based on configuration information stored in the computers’ CMOS memory). Once the operating system is loaded, the computer can understand & respond to your input, display output, run software & access your data.

CMOS memory (pronounced “SEE moss”, stands for Complementary metal oxide semiconductor but no need to memorize that).

A type of integrated circuit that holds data, but requires very little power to retain its contents. Because of its low power requirements, a CMOS chip can be powered by a battery (i.e. CMOS is also volatile) that’s integrated into the motherboard. The battery trickles power to the CMOS chip so that it can retain vital data about your computer system configuration, even when your computer power is turned off. In many of today’s microcomputers, the CMOS chip is housed within the same chip carrier as the ROM BIOS.

 

When your system configuration changes, the data in the CMOS memory must be updated. Some operating systems have a special utility, or feature, called “plug and play” that automatically updates the configuration information in CMOS when hardware components are upgraded or new peripherals are added, e.g. you install a new hard drive.

Virtual Memory

 

A computer's ability to use storage space on a hard disk drive to simulate RAM.

Virtual memory allows computers without sufficient amounts of real memory to run large programs, manipulate large data files, and run multiple programs simultaneously. It does this by temporarily writing the contents of the least-used sections of RAM to the hard drive to free up RAM memory when needed. For example, if you are running a word processing program and open a spreadsheet program, the operating system frees up memory, as needed, by copying the contents of the least-used memory segments used by the word processing instructions and data to the disk; thereby creating space for the spreadsheet program and its data. (This is one example of the operating system managing the computer system’s resources).

Virtual memory is not as fast as RAM, because your computer takes longer to retrieve data from virtual memory because the disk is a mechanical device (vs. an electronic circuit).

Like data held in RAM, data in virtual memory becomes inaccessible if the power fails. Data in virtual memory is not erased from the disk if the power fails, but the instructions that direct the computer to the location of virtual memory are stored in RAM and are lost when the power fails.

Cache

Special high-speed memory that gives the CPU more rapid access to data than from memory located elsewhere on the motherboard (also called RAM cache or cache memory). A very fast CPU can execute an instruction so quickly that it often must wait for data to be delivered from RAM, which slows processing. As you begin a task, the computer anticipates what data the CPU is likely to need and loads this data in the cache area. When an instruction calls for data, the CPU first checks to see if the required data is in the cache. If so, it takes the data from cache instead of fetching it from RAM, or the hard drive (even slower).

 

Note: disk drives typically also have memory devices, i.e. caching mechanisms, built in to speed up access to data on the disk.

The Boot Process

 

The sequence of events that occur when you turn the power to your computer on. They are:

  1. Power up – power distributed to fan, motherboard and peripheral devices
  2. Start boot program – the microprocessor begins to execute instructions stored in ROM BIOS
  3. POST – the computer performs diagnostic tests of crucial system components (based on configuration data stored in CMOS)
  4. Load operating system – operating system instructions copied from disk to RAM
  5. Check (operating system related) configuration and customization – the microprocessor reads configuration data and executes any customized startup routines specified by the user
  6. Ready – the computer is ready for user input.

POST (Power-on Self-test)

A diagnostic process that runs during startup (i.e. boot process) to check components of the computer such as the graphics card, RAM, keyboard and disk drives. The computer tests RAM by placing data in each memory location (i.e. address) in RAM, then retrieving that data to see if it is correct. The computer then displays the amount of memory tested on the monitor. When it checks the disk drives you will see the drive activity lights flash on for a moment, and you will hear the drives spin.

Safe Mode

A menu option that appears when Windows is unable to complete the boot sequence. It is a limited version of Windows that allows you to use your mouse, keyboard and limited use of your monitor, but no other peripheral devices. This mode is designed for troubleshooting. By entering safe mode, a user can gracefully shut down the computer, and then try to reboot it.

Peripheral Device

Components and equipment that expand a computer’s input, output, and storage capabilities. By some definitions this includes devices that are included with most basic computer systems, such as keyboards, monitors, disk drives and mice, but also include devices that extend a computer’s capabilities, such as a printer, scanner, and modem.

Computer Program & Software

Computer Program - A set of detailed, step by step instructions that tells a computer how to solve a problem or carry out a task.

 

Software – The instructions, and associated data, stored in electronic format that set up a computer to do a task, indicate how to interact with a user, and specify how to process data.

Operating System (OS)

The software that controls the computer’s use of its hardware, or system, resources such as memory and disk storage space. An OS is essentially the master controller for all of the activities that take place within a computer.

System Resource

A system resource is any part of a computer system, such as disk drive space, memory capacity, processor time, or peripheral devices that might be used by a computer program. An operating system allocates system resources so that programs can run efficiently.

Multitasking

Multitasking - A service provided by an operating system that allows two or more programs to be run at the same time.

User Interface & GUI (pronounced “gooey”, Graphical User Interface)

A user interface includes the software and hardware that enable people to interact with the computer. A graphical user interface is a type of user interface that feature on-screen objects such as menus and icons that may be manipulated using a mouse. They are based on the philosophy that people can use computers intuitively, i.e. with minimal training, if they can manipulate on-screen objects that represent tasks or commands.

 

GUIs often display menus and prompts (the latter may be in the form of dialog boxes and wizards) in addition to graphical objects, because graphical user interface designers found it difficult to design icons and tools for all possible tasks. Typically, all of the commands for a software program will be listed in the menus. The commands that tend to be used most frequently might also be represented by graphical objects that provide a quick shortcut for carrying out a task (e.g. toolbar buttons).

Icon

Graphical representation of an object such as a disk, printer or program.

Document production software

Computer programs that assist the user in composing, editing, designing, printing or electronically publishing documents. Other features typically provided include:

  • the ability to type content and then edit text afterwards
  • search & replace functions to fix multiple instances of a problem easily
  • formatting features such as the ability to add graphics, title pages, TOC, indexes, font & paragraph styles, headers & footers, page #s, tables, etc.

Document Template

A preformatted document into which the user types text. In a document template, format settings such as margins, line spacing, heading fonts or styles, type size and page layout have typically been set up for you. A template document may also contain labels, boilerplate text or instructions.

Document Wizard

A wizard provides you with a document format, just as a template, but also prompts a user, in a step-by-step fashion/sequence, for data or information to be inserted into the resulting document.

Text Blocks & White Space

You can easily insert text, cut sections of text, and move entire paragraphs or pages to improve the structure and logical flow of a document. In document production terminology, sections of your document are sometimes referred to as Text Blocks. The open areas between these text blocks are known as white space and represent an effective tool for improving readability of a document.

Search & Replace

A feature of documentation production software that allows the user to automatically locate all instances of a particular word or phrase and substitute another word or phrase for it.

Tables

A structure, enabling the arrangement of text, data or pictures into a grid of rows and columns. In addition to serving a purpose for formatting certain information, they are also useful in building page layout structure (whether it is a Word document or HTML page).

HTML (Hypertext Markup Language)

A standardized, text-based, format used to display documents that will be used as Web pages. HTML consists of a set of codes, known as “tags”, that can be inserted into a document. A special class of application software, known as a web browser, then interprets those tags and renders the page with its text, graphics and links appropriately.

Spreadsheet

A numerical model or representation of a real situation, presented in the form of a table. A spreadsheet works well for recording and graphing data, for making calculations, and for constructing numerical models of the real world. The main advantage of spreadsheet software is the time it saves – once you create a worksheet, you can change your data without redoing your calculations. In addition, worksheet data is stored in electronic format, so it can be merged with word processing documents, posted on the Internet, or transmitted as part of an e-mail message.

File Management software

Software, such as Windows Explorer, that helps users locate, rename, move, copy, and delete files (and folder).

Directory, Root Directory & Folders

An operating system maintains a list or index called a Directory of the files on each disk or storage device. A directory contains information about every file on the storage device, including the filename, the filename extension, the date and time it was created, and the file size. The terms directory and folder are often used synonymously. The main directory, or folder level, of a disk is referred to as the root directory. Any given directory, or folder, is often divided into other sub-folders or sub-directories for organizational purposes. When viewing a folder, at any level, you can see (and manage) the files and sub-directories that it contains.

File Specification

A combination of the drive letter, subdirectory (ies), filename, and extension (also known as “file type”) that identifies a file. For example, given the file specification “A:\word\mydocs\myresume.doc”:

“A:” is the drive letter

“Word\mydocs” is the subfolder

the “\” (backslash) character is used to separate the directory levels

“myresume” is the File name

“.doc” is the file extension, or file type, which indicates the native file format.

 

A file specification is sometimes referred to as a file path.

Executable File

Executable - A file, usually with an .exe extension, containing instructions that tell a computer how to perform a specific task. These types of files include operating system, utility and application software programs. To use an executable file, such as an application program, you “run it” or “start it”.

 

 

Motherboard

The main circuit board in the computer that houses the chips that control the processing functions. Chips may be soldered on the motherboard or plugged into the board. Chips, or cards, that are plugged into the motherboard may be upgraded. These include the microprocessor chip (CPU), as well as chips for memory (RAM) or that handle basic input and output (ROM). Circuits are etched into the motherboard and act like wires, providing a path so the computer can transport data from one chip to another as needed for processing.

Data Bus

An electronic pathway or circuit that connects the electronic components (mainly the processor and RAM) on a computer’s motherboard.

Expansion Slots

The motherboard also contains expansion sockets (or slots) that allow you to plug in circuit boards, called expansion cards. A computer usually contains sets of different types of slots.

Expansion Card

A circuit board that is plugged into a slot on a PC motherboard in order to add extra functions, devices, or ports. For example, a video, sound or network interface card. Any given card is manufactured to fit in a specific type of expansion slot. Also known as an “expansion board”.

Expansion Port

A socket, located on an expansion card, into which the user plugs a cable from a peripheral device, allowing data to pass between the computer and the peripheral device.

Expansion Bus

The segment of the data bus that transports data between RAM and the peripheral devices. That is, it connects RAM to the expansion slots/cards, which in turn are connected to peripheral devices through their expansion ports(s) and the cables. All input & output travels through such a path.

Bit, byte, ASCII & the Binary number system

As microcomputers are digital devices, all data, information, programs, graphics, music, etc. are stored as a digital series of 1s and 0s. A bit is the smallest unit of information handled by a computer. By the above definition then a bit can hold one of two values, either a 0 or a 1. Eight bits comprise a byte which, by use of coding mechanisms, can represent a letter or number. ASCII is the coding system used to represent characters, while the Binary number system is a method for representing numbers using only two digits.

Network Interface Card or NIC (pronounced “nick”)

A NIC is the key hardware component for connecting a computer to a local area network (LAN). It is a small circuit board/card that sends data from a workstation out over a network, and collects incoming data for the workstation. Every device must have one in order to connect to a network. It is sometimes built into a device; otherwise an NIC expansion card is required.

Computer Network

A computer that is not connected to a network is referred to as a “stand-alone” computer. When you physically connect your computer to a network, typically using a cable, your computer becomes a workstation on the network. In this scenario, your workstation provides you with your computer’s usual resources, referred to as local resources, such as its hard drive, software, data and printer. In addition, you also have access to network resources, which typically include application software, storage space for data files, and printers other than the one connected to your local computer.

 

Sharing programs on a network is effective for several reasons. First, less disk storage space is required because the program is stored only once on the server, instead of being stored on the hard disks of multiple stand-alone computers (assuming multiple people use the program). Second, when a new version of the software is released, it is easier to update one copy of the program on the server than to update many copies stored on stand-alone computers. Third, purchasing a software license for a network can be less expensive than purchasing single-user licenses for each workstation on the network. When an application is run from a network server, the program is downloaded to the local workstation’s RAM. It then works just as if you had run the program locally.

Sharing data files on a network is effective because if you store a file on your local hard disk, you can typically only access the file from your workstation. However, if you store the file on the hard disk of a server, you can access the file from any workstation on the network. Other network users can also access the files that you have stored on the server, but most networks provide you with the option of restricting access to files as necessary. Finally, most network installations schedule automated backup of the files and programs running on the network servers, thereby minimizing the risk of loss of valuable information.

Drive Mapping

(not on final exam)

In network terminology for assigning a drive letter to a network server disk drive. For example, the network login process might automatically map a server hard drive by assigning the letter ‘F’ to it (or you can manually map a drive in Windows explorer).

 

Once a drive letter has been mapped, you can access data files and application software from that drive just as you would from your local hard disk drive.

E-mail System

The collection of computers and software that work together to provide e-mail services.

E-mail Address

The network address for an individual’s e-mailbox. Usually the user’s network ID, an @symbol, and the name of the e-mail server.

E-mail Message

A computer file containing a letter or memo that is transmitted electronically via a communications network. More simply stated, it is a document sent electronically from one user to another.

E-mail Attachment

A separate file that is transmitted along with an e-mail message.

Store-and-forward technology

A technology used by communications networks in which an e-mail message is temporarily held in storage on a server until it is requested by a client computer. In other words, e-mail messages are stored on a server. When you want to read this mail, the server forwards your messages to your workstation. Hence, your workstation does not need to be turned on when someone sends an e-mail message to you. In many ways, an e-mail system works like the traditional postal system. The server that stores your mail is similar to your local post office because it holds your mail until it can be delivered to your house.

 

Depending on the e-mail client software that you are using, the messages may remain on the e-mail server or they may be downloaded to your workstation and removed from the server. Usually, web browser based e-mail systems maintain the message on the e-mail server, while e-mail clients download your messages, by default, to your workstation (although you may often set options to maintain a copy of your messages on the server also).

 

The benefit of browser based e-mail clients is that you can easily access your e-mail from any workstation having Internet connectivity. However, custom e-mail client software tends to provide more robust functionality. In addition, some e-mail systems limit the amount of storage space that your e-mail messages may use on the server. If you go over the limit, it may prevent you from receiving additional e-mail or delete your oldest messages to free up space.

 

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