John Cletheroe's
PC And Internet Hints

PC And Internet Glossary - Including File Extensions - C

C, C+, C++, C#, Visual C

Variants of the C programming language. The original C language was extremely difficult to learn and use, being very close to machine code and using some bizarre and inconsistent syntax. However, when used skilfully it could create programs which ran extremely quickly. I haven't explored any of C's more modern versions.

A serious problem with the original version of C was the almost total lack of error trapping, causing any program bug to crash the program and in the case of Windows, probably the operating system as well.

C was the original version of the language. One of the best known versions was Borland's Turbo C.

C+ appears to be a short-lived enhanced version of C.

C++ is an object-oriented version of C.

C# is an object-oriented version of C published by Microsoft, said to be very similar to Java.

Visual C is a Microsoft version of C with a complete graphical integrated development environment, similar to that of Visual BASIC.

C:\WINDOWS\TEMP

The folder used by most programs to store their temporary files. These files should be automatically deleted after use but if a program is badly written, if a program crashes or if the computer locks up then this may not be done. Therefore it is well worth deleting all the folders and files in C:\WINDOWS\TEMP - but not C:\WINDOWS\TEMP itself - every so often. Shut down all programs before doing this in case they have any legitimate files open in C:\WINDOWS\TEMP. See also TMP.

ca

The Internet top-level domain for Canada (and not California, as you might perhaps think).

CA

Certificate Authority. An organisation which issues digital identity certificates. A certificate authority is usually a company that, for a fee, will issue a public key certificate which states that the CA attests that the public key contained in the certificate belongs to the "owner" noted in the certificate. A practical difficulty with this system in the real world is that most users will be completely unfamiliar both with the digital certificate concept and the names of certificate authority companies.

CAB

"Cab". File extension. Cabinet File. A Microsoft variant on the PKZIP concept. The files within a CAB file could be of any type and therefore could contain viruses.

Cable Modem

A device for interfacing a PC with a cable television line. Cable modems offer very high speeds. I am not sure if cable modems can be used in the UK yet or not.

Cache

"Cash". Any area of high speed storage used to store most recently accessed data in the hope that it may be required again soon. Examples include the relatively small cache in modern processors, areas of memory in PC's and hard disk cache areas on some ISP servers for commonly accessed web page files.

L1 cache, level 1 cache and primary cache are names for the small amount of high speed cache memory included in all modern processor chips. Typically 32KB or 64KB of static ram.

L2 cache, level 2 cache, secondary cache and external cache are names for the larger and slightly slower cache memory fitted to all modern PC's. Typically 256KB or 512KB of dynamic ram.

Caption Buttons

In the list of items in Control Panel > Display > Properties > Appearance, the name "Caption Buttons" refers to the Minimise, Maximise/Restore and Close buttons located at the righthand end of window title bars, and the "What's This" ("?") and Close buttons located at the righthand end of dialog box title bars. Therefore caption buttons are not command buttons.

Carat

A common mis-spelling of caret.

Caret

  1. ^ (see that entry).

  2. The text cursor; normally a black, blinking vertical line between two characters. Also called the insertion point, since it indicates where text will be inserted when you type.

CAS-Latency

See "CL Numbers".

Case

  1. Lower case means small letters. Upper case means capital letters.

  2. A statement in many programming languages which provides multi-way branching, depending on the value of a specified variable. This avoids having to write a lengthy set of IF - THEN - statements.

  3. CASE (in upper case): Computer Aided Software Engineering. A short-lived fad in the late 1980's or early 1990's, around the time that Structured Programming, Fifth Generation Languages and Oracle's myth of getting normal users to understand SQL were prevalent. CASE involved drawing complicated "crow's feet" diagrams showing the relationships between files and getting users to agree to them. As the users (and most of the system analysts and programmers) hadn't got a clue what the diagrams meant, the idea didn't survive very long.

Case Sensitive

An indication that it matters whether you enter an item in lower case or upper case. Most passwords and URL's are case sensitive. File names in DOS and Windows are not case sensitive.

Cast

In the C programming language, a function which converts data from one variable type to another, in the same way as the STR$ and VAL functions do in BASIC. The C Cast function has angle brackets round its parameters, not the normal round brackets.

Catalyst and Catalyst Control Centre

Display drivers and associated configuration software for ATI video boards, published by ATI. Confusingly, users looking for drivers on the ATI web site should download Catalyst.

Category x Cable

These definitions are from an article which appeared in the 15-May-02 edition of the LockerGnome email newsletter.

CC

  1. Carbon copy. A list of recipients of an email message in addition to the main list. For example, you might need to send a copy of a message to your manager as well as the main recipient, in order to keep them informed of a situation.

  2. Closed Captioning. In American television, a system whereby subtitles are transmitted via a method similar to teletext.

  3. Creative Commons. I'm not sure what this organisation's purpose is, and its web site doesn't explain it at all well. It appears to be some sort of copyright licensing organisation. External link verified May-04.

CCITT

Comité Consultatif International Téléphonique et Télégraphique. An organisation that sets international communications standards.

CD

  1. Compact disk.

  2. Change directory (an MS-DOS command).

CD Ripper

See DAC.

CD-R

A CD recording system which only allows a disk to be written to once. See also CD-RW.

CD-ROM and CD-ROM XA

CD-ROM, sometimes called Mode 1, refers to a CD with one session (it may have one or more than one track).

CD-ROM XA, sometimes called Mode 2, refers to a CD with more than one session (or currently with one session but capable of having additional sessions added later).

I believe that strictly speaking referring to CD-ROM as being Mode 1 and CD-ROM XA as being Mode 2 is not quite true. However, this usage is common.

CD-RW

A CD recording system which allows disks to be written and re-written, in the same way as magnetic disks can be (although at a much slower speed). I believe that CD-RW disks must be erased before they can be written on again, and that there is a finite limit to the number of times this can be done. CD-R and CD-RW disks, players and writers are different to each other, although most modern drives can handle both types of disks, as well as being able to read conventional mass-produced audio CD's and CD-ROM's. See also DVD.

CDA

File extension. When a digital audio CD is examined in Windows Explorer (etc) a CDA file is listed for each track. Double-clicking on a CDA file will start the Windows CD Player program and play the track. However, the CDA files are only 44 bytes long and are therefore shortcuts to the actual track information which doesn't appear in the directory listing. Copying a CDA file will not copy the music - to do that you need to use a CD Ripper (DAC) program. CDA files cannot contain viruses.

CDDB

A database of audio CD's, listing artist names, album names and track names, keyed by each CD's serial number. Some audio CD related programs can access this database via the Internet and obtain the relevant information from it, relieving the user of the task of entering the information manually. Unfortunately some of these programs constantly attempt to access the database even if would you prefer them not to, which is a considerable pain. I don't know what CDDB stands for: "compact disk database" seems a reasonable guess.

CDFS

In Windows, the file system driver for CD-ROM drives.

CDMA2000

The system used in 3G mobile phone networks in the USA and Canada.

CDO

Collaboration Data Objects, or Collaborative Data Objects. Associated with Outlook and possibly some other Microsoft programs.

CDP

  1. Certificate Distribution Point or CRL Distribution Point. See CRL.

  2. File extension. See this entry on my Trainz Wordz page.

CDP2

File extension. See this entry on my Trainz Wordz page.

CDR

File extension. Corel Draw data file.

CDT

File extension. Corel Draw data file.

CE

A version of Microsoft Windows for PDA's (personal digital assistants, tiny handheld computers).

Celeron

A range of Intel processors, relatively low performance and low cost.

Centrino

A range of Intel processors and associated chips for portable computers, which according to some sources provides built-in wireless networking capability.

CER

Canonical Encoding Rules. Associated with ASN.1 (see that entry).

CERT

(United States) Computer Emergency Readiness Team, a division of the US Department of Homeland Security. Amongst other things, CERT offer free security alert bulletins via email. Sometimes referred to as US-CERT.

Certificate

An electronic means of the proof of identity, for example of an email address or a web site. I think certificates operate by means of the public-private key mechanism, the idea being that only the person knowing their own private key could have encoded the message but anyone knowing the public key can decode it. Since certificates are issued and distributed electronically, and displayed using PC software and operating systems, it is very difficult to see how they can possibly be regarded as being reliable. I think "certificate" is another name for "digital signature".

CES

The Consumer Electronics Show, which takes place each January in Las Vegas, Nevada.

CFM

File extension. According to one source you can change a CFM's file extension to PDF and it will open in Adobe Acrobat Reader.

CG:

Microsoft KnowledgeBase article title prefix for articles relating to Microsoft's ClipArt Gallery.

CGI

Common Gateway Interface.
  1. A method by which web pages can exchange messages with programs running on their server, for example to handle forms. Such programs may be written in languages such as PERL.

  2. File extension. An HTML file created by a program running on the server in conjunction with CGI, often in combination with a database. I think that CGI files might be capable of containing JavaScript and Visual BASIC script programs which could include viruses - although browsers should prevent such programs from performing inappropriate actions.
See also ASP and PHP, which are alternative methods of achieving much the same effect.

CGM

File extension. Computer Graphics Metafile. A type of clipart file. CGM files cannot contain viruses.

Channel

  1. One section of a large web site.

  2. A push technology web site.

  3. Selling through conventional means such as distributors, shops and mail order, rather than selling direct as companies such as Dell do.

Characters per Inch (CPI)

An old method of specifying the size of printer fonts, commonly used with dot-matrix printers before the introduction of Windows. Now replaced by specifying the font size. With font sizes, the larger the number the larger the characters. With characters per inch, the larger the number the smaller the characters.

Chat, Chatroom

A facility whereby two or more people can type messages to each other in real time over the Internet.

Opinion: A very good way of running up a huge phone bill.

Chip's Challenge

A very highly recommended game, included in Microsoft's Windows Entertainment Pack. Chip's Challenge has simple 2D graphics but a very rich set of game elements which permits the creation of levels with very different styles. Some levels involve pure logic, some require a map to be created and some are pure monster dodging. A search on the net should reveal sources of additional levels and even a level editor, but for copyright reasons the main program is not so easily obtained.

CHK

File extension. A recovered file created by Scandisk, the program which detects and corrects directory corruptions. CHK files could contain viruses.

CHM

File extension. Compiled HTML file. The new style of Windows Help file used with Internet Explorer V4. Also called HTML Help. See also HLP. CHM files can contain instructions which could perform undesirable operations on a computer.

Opinion: I must question the need for another Windows Help file system, especially one which is slower and even more user-hostile than the original system.

CHUMP

File extension. See this entry on my Trainz Wordz page.

CHW

File extension. A type of Help index file, presumably associated with CHM files. According to Microsoft KnowledgeBase article 275539 CHW files are rebuild as required and can therefore be deleted. I don't think that CHW files can contain viruses.

CIL

Common Intermediate Language. The method by which .NET runs programs written in various languages. The original source code is translated into a CIL called MSIL (Microsoft Intermediate Language). This step requires a different translation routine for each language. Then the MSIL coding is executed on a single virtual machine.

CIM

Common Information Model. A Microsoft term for which I have not yet found an explanation.

CIW

Custom Installation Wizard. Used in Microsoft Office 2000's installation procedure and probably those of some other Microsoft products.

CL Numbers (CL2, CL2.5, CL3, etc)

In memory (RAM) specifications, a measure of the CAS-Latency. There are other, less significant latency numbers. The lower the CL number the faster the memory operates, although according to most sources differences in CL numbers have little effect on the actual performance of most modern computers.

Memory speed parameters are usually quoted as clock cycles, in decreasing order of importance, with dashes between figures, as follows:

CAS Latency (CL) - RAS to CAS (tRCD) - RAS Precharge (tRP) - Active to Precharge (tRAS)

See also "DDR Numbers" and "PC Numbers".

Class

  1. A term used in object oriented programming languages, for example Java. Classes are templates from which individual copies (instances) of objects are created. A class can be either a program in its own right or a subroutine used in a program.

    WordPad is a simple word processor program supplied with Windows 95/98. When it starts it very briefly displays a title windows which includes the wording "Microsoft Foundation Classes V3.2". I think this means that the program includes classes in the object oriented programming sense, not that the program was developed by trainee programmers or that it was initially developed for use in educational establishments. The abbreviation MFC means Microsoft Foundation Classes.

  2. File extension. Java class, in other words a compiled Java program or subroutine. Java class files tend to be numerous but small. Collections of Java files are often distributed as PKZIP/WinZip ZIP archive files, usually with an extension of ZIP but sometimes with an extension of JAR (Java Archive) or CAB (Cabinet). Normally the contents of these files do not have to be extracted before they can be used. Class files, being programs, can contain viruses. Therefore ZIP, JAR and CAB files containing Class files can contain viruses. However, in theory the Java Virtual Machine which runs compiled Java programs should protect a computer from any malicious coding.

ClearType

An optional feature in Windows XP which is claimed to make text more readable but which actually makes it appear very fuzzy and out of focus, making it much more difficult to read.

CLI

  1. Command line interface. A style of operating a program where the user types in commands rather than by means of a mouse or a menu system. Many old programs and operating systems used this method of operation.

  2. Common Language Infrastructure. Part of .NET, and very closely associated with the CLR (Common Language Runtime).

Click-through

Clicking on a banner advertisement on a web page, for example on a search engine. The click-through rate is the percentage of users who click on the advert.

Clicks and Bricks

An informal name for the type of traditional company which now also dabbles in e-commerce as a sideline, often in a very amateurish manner.

Client

  1. A normal PC operating as a workstation, as opposed to a server.

  2. A network-related program running on an end-user's computer. Examples include any web browser or email program. An "email client" is simply an email program or a web browser with integrated email facilities.

Client-Server

The current nearly universally used style of computer system, where computers used by users (clients) communicate over a network with computers holding shared information (servers). The client-server style of computer system replaced the old mainframe computer and vdu style during the 1980's and 1990's.

Clip-Art

Cartoon-like drawings.

Clipboard

The area of memory used to hold items when they are cut or copied, and from which they are pasted. The clipboard can hold a various of types of material including not only sections of text but also images and (in Windows 95/98 Windows Explorer) files. Also called the cut and paste buffer.

Closed

The "on" position of a switch, since then the electrical circuit is connected.

CLR

  1. In some programming languages, a command which clears the screen. Other languages tend to use a command called CLS to perform the same operation.

  2. In some programming languages, a command which erases the variable table, so as to clear the values of all variables.

  3. Common Language Runtime. The virtual machine which runs MSIL (Microsoft Intermediate Language) coding. CLR is part of .NET Framework. This page on GotDotNet.com offers some information on the subject but unfortunately it assumes familiarity with .NET concepts. External link verified May-04.

CLS

  1. File extension. Class module. A file associated with some modern programming languages. For example, a Visual BASIC class module (associated with version 6 of Visual BASIC). I do not know whether CLS files can contain viruses or not.

  2. A command in BASIC which clears the screen.

CLSID

Class Identifier (presumably). A unique 64-bit number (or, according to other sources, a 128-bit number) usually quoted in hexadecimal, sometimes inside curly brackets, associated with each OLE Automation object. The Registry holds a list of installed OLE Automation objects, their CLSID's and their other properties. According to one source CLSID's are URL's and that CLSID's are one type of UUID (Universal Unique Identifier) associated with Microsoft's COM (Component Object Model), and that other different types of UUID's are used for Java. A CLSID is a globally unique identifier that identifies a COM class object. I don't know how uniqueness is achieved (perhaps only Microsoft can issue numbers). I suspect that a program will first look on the same PC to see if the requested object has already been installed, and if not then it will download and install it, although how it knows where to go to obtain it is a mystery to me (perhaps they are only available from Microsoft).

Cluster

  1. The connecting together of two or more computers so that they share their processing and disk accessing operations. Ideally clustering should also allow the system to continue operating if some components fail.

  2. A unit of disk space. Space on disks is allocated to files one cluster at a time, a cluster consisting of a number of blocks. Sometimes called disk allocation unit or allocation unit. Since directory systems have a limit on the number of clusters they can handle, larger disks have larger cluster sizes and so more space is wasted at the end of each file. Every so often Microsoft increases the number of clusters its directory system can handle, solving the problem for a while until hard disk sizes increase again. See also FAT and FAT32.

CMD

File extension. Microsoft Windows NT Command script. CMD files can contain instructions which could perform undesirable operations on a computer.

Cmdninst.exe

The Configuration Manager Device Installer launcher in Windows ME, and maybe also in other versions of Windows. See Microsoft KnowledgeBase article 277994.

CMOS

Complementary Metal Oxide Silicon. The most common form of Non-volatile RAM (see that entry).

CMS

  1. Content management system, a script or program for maintaining a web site.

  2. Code management system, a script or program for archiving and maintaining source code.

CNP

Card Not Present. A credit or debit card transaction carried out over the phone, by fax, by mail order or via the Internet, in which the seller does not physically see the card.

CNT

File extension. A file associated with a Windows Help HLP file (contents???). CNT files cannot contain viruses.

co.uk

The Internet domain for commercial organisations (companies) in the United Kingdom.

COAST

Cache On A Stick. A memory module, somewhat similar in design to a SIMM, for secondary cache memory. Found in some but not all modern PC's.

Code

  1. A sequence of commands written in a programming language.

  2. A means of representing characters as numbers, for example ASCII.

Codec

Coder/Decoder (or Compressor/Decompressor). A software module (library routine, similar to a DLL) associated with playing and recording sound files (and probably also video files). There are separate codecs for each file format.

ColdFusion

A program which runs on a server and which creates web pages on demand by extracting information from a database. There are many other similar programs.

Collection

A term used in Microsoft's style of object oriented programming. A collection is an object that contains a set of related objects, making it easier to work with the objects as a set. For example, you can use a "For Each" loop to perform the same operation on each object in the collection.

Colon

: (see that entry).

COM

"Com".
  1. The Internet top-level domain for commercial organisations (companies). Most but by no means all .com web sites relate to US or multinational companies.

  2. File extension. Compiled Object Module (?). A type of compiled (executable) program file, used for very small MS-DOS programs under 64KB in size (larger programs are EXE files). Now largely historical. COM and EXE files can contain viruses.

  3. Component Object Model, or sometimes Common Object Model. Very closely related to ActiveX, I think. COM was the successor to OLE (Object Linking And Embedding), and has in turn now been replaced by .NET.

  4. An RS-232 communications port, for example COM1: or COM2:.

Compile

To convert a program from a high level language to machine code. A program which performs this process is called a compiler. "Make EXE" is Microsoft's jargon for "compile".

Compiled HTML

See CHM.

Compute With Fruit

A colourful way of saying that someone uses an Apple computer.

CONFIG

  1. File extension. In .NET, a file used to store application configuration settings.

  2. File extension. In .NET, a file used by ASP.NET to store the configuration settings for a web project.

Configmg

The Windows Configuration Manager in Windows ME, and maybe also in other versions of Windows. See Microsoft KnowledgeBase article 277994.

Connector

Microsoft KnowledgeBase article 824684 includes the following definition of this term as used by Microsoft: "A connector is a software component that is designed to support connections between software."

Connection

Windows uses the word "connection" in a potentially very confusing way. Instead of referring to a physical connection, in Windows a "connection" is a set of network, wireless network, or Internet configuration settings. It is quite possible for more than one Windows "connections" to all use the same physical connection from a computer via a modem or router to the Internet, for example if more than one ISP account is used from the same computer. Windows does not use this terminology when referring to the configuration settings of any other physical interfaces or ports.

Console Application

In the jargon used by modern Microsoft programming languages, a console application is a program which runs in a DOS window.

Contacts

See Address Book.

Control

In Visual BASIC, any object which can be placed on a form (window) and which will react in some way when the user clicks on it, drags it, etc. Examples include command buttons, text boxes, scroll bars, picture boxes, check boxes, option buttons and additional custom controls (now called ActiveX controls).

Cookie

A small file stored on your computer noting details such as your preferred style of display for a web page (frames or non-frames, for example), or your username. Many users regard cookies as an invasion of privacy and a serious security risk; however many web sites will not work unless you permit cookies to be saved on your computer. Probably the best compromise is to block third party cookies, as follows:

Core

  1. With a lower-case c, a core is the central part of a processor, its arithmetic and logic elements. Traditional processors had one core. Modern processors may have one, two or four cores.

  2. With an upper case C, Core is a range of Intel processors, coming in sequence after the Pentium range. Core 2 is the second version of the Core range. All Core processors may potentially have one core ("Solo"), two cores ("Duo") or four cores ("Quad"). Thus very confusingly "Core 2" does NOT mean the same thing as "dual core".

CPI

See Characters per Inch

CPL

File extension. Control Panel file. Each Control Panel option is handled by a corresponding CPL file. Sometimes called a Control Panel Applet. According to one item of Microsoft documentation, CPL files are a special type of DLL file. CPL files can contain viruses.

CRC

See Cyclic Redundancy Check.

Creative Commons

See CC.

Critical Update

Microsoft KnowledgeBase article 824684 includes the following definition of this term as used by Microsoft: "A critical update is a broadly released fix for a specific problem that addresses a critical, non-security-related bug."

CRL

Certificate Revocation List. Associated with Outlook Express 6, Outlook 2000, and possibly other programs.

CRM

Customer Relationship Management. I think this may refer to software which tracks customers' purchasing habits as recorded by supermarket loyalty cards.

CRT

  1. Cathode Ray Tube.

  2. File extension. Security certificate.

CS

  1. File extension. Visual C# .NET assembly information file.

  2. File extension. Visual C# .NET class.

  3. File extension. Visual C# .NET code file.

  4. File extension. Visual C# .NET COM class.

  5. File extension. Visual C# .NET component class.

  6. File extension. Visual C# .NET custom control.

  7. File extension. Visual C# .NET data form wizard.

  8. File extension. Visual C# .NET inherited form.

  9. File extension. Visual C# .NET inherited user control.

  10. File extension. Visual C# .NET installer class.

  11. File extension. Visual C# .NET transactional component.

  12. File extension. Visual C# .NET user control.

  13. File extension. Visual C# .NET web custom control.

  14. File extension. Visual C# .NET web form.

  15. File extension. Visual C# .NET web service.

  16. File extension. Visual C# .NET Windows form.

  17. File extension. Visual C# .NET Windows service.

CSR

Certificate Signing Request. Associated with Digital Certificates, I think.

CSS

  1. Cascading Style Sheet. A method of specifying the format of web pages, usually in a separate file.

  2. File extension. A cascading style sheet file.

  3. Cross Site Scripting (for which the abbreviation XSS is more commonly used, so as to avoid confusion with cascading style sheets).

CSV

File extension. Comma Separated Values. A file format occasionally used to export/import unformatted data between different programs. Basically an ASCII text file, with one record per line, fields separated by commas and if necessary enclosed by double-quote characters. CSV files cannot contain viruses.

CTD

Crash To Desktop. When a program quits unexpectedly by itself due to a bug.

CTL

File extension. Visual BASIC V6 User Control file. I do not know whether CTL files can contain viruses or not.

CTRL

Two keys on the keyboard used in conjunction with other keys or the mouse.

CTS

See RTS/CTS.

CTX

File extension. Visual BASIC V6 User Control binary file. I do not know whether CTX files can contain viruses or not.

Curly Brackets

{ and }

CUR

File extension. Custom cursor. The graphic image of a special mouse pointer or text cursor, presumably.

Cursor

  1. The indication of the position of the mouse on the screen. The shape sometimes changes to indicate the program's current mode or the nature of the object under the mouse.

  2. The indication of the position of the "insertion point" in text, in other words where text will appear when you type. Normally a black vertical flashing line between two characters. This cursor is sometimes also called the caret.

  3. In modern database terminology, the word cursor has a totally unrelated and therefore extremely confusing meaning, namely the currently selected record or records in a file.

Custom Control

In Visual BASIC, an additional type of object beyond those offered by the language by default. See OCX and VBX.

Cut and Paste Buffer

See clipboard.

CVF

Compressed Volume File. A file which holds a compressed disk volume.

CVS

Concurrent Versions System. A term used in the Open Source/Java/Linux world to refer to a computer system which attempts to allow multiple programmers to work on the same project and merge their results. The concept strikes me as an instant recipe for potential total disaster. I'm not sure whether CVS is a general term, a product name, or a product name which has become a general time (in the same way that "Hoover" is a general term for all makes of vacuum cleaner).

See also "Repository".

CW

Corporate Workgroup. A mode of Outlook 2000 (and possibly other versions of Outlook), the other mode being IMO (Internet Mail Only). I think the mode is chosen when the program is installed, and there may be a third "no email" option.

Cyclic Redundancy Check (CRC)

An error detection system used in some data storage and data transmission systems. A type of parity check, I believe. I don't think CRC can correct errors, only detect them.
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