| Term | Description |
| C: | A letter followed by a colon is used to designate a drive (physical or virtual) on your computer. C: drive is usually the hard drive inside the case that your computer boots from (contains the operating system files). |
| Cab File | A cabinet file contains several or many compressed files. These files are generally used to distribute software on disk and have a .cab file extension. Most of the files for Windows95/98 are in Cab files on the Setup Disk. The Extract command is used to extract one or more files from the cabinet file. |
| Cable | Wires or a bundle of wires in a protective plastic or rubber covering, with connectors used to join the different components, peripherals and resources associated with your computer system. |
| Cache | An area of high speed memory set aside to store frequently accessed data. When data is accessed, a copy (and its address in memory) is stored in cache memory. The next time the CPU looks for information, it first checks the cache. If the data is there (called a hit), it can retrieve it from the much faster cache memory. If it is not, then it accesses system memory, puts a copy of the new data in the cache, and processes the information. Disk caching and memory caching significantly improves the overall speed of the computer but there are limits. |
| CAD | Computer Aided Design - See CAD/CAM. |
| CAD/CAM | Computer Aided Design/Computer Aided Manufacturing. The use of computers to design and manufacture a product. The product is designed on a computer (using a CAD program) and then built or assembled using computers designed specifically for that process. |
| Calibrate | The process of testing a measuring device (such as a joystick) and then manipulating or changing its settings to conform to a set standard ensuring the device is working accurately. |
| Cancel | A button in most dialogue boxes in a graphical user interface that will exit the box without making any changes. Any settings that were changed will return to what they were before the box was open. |
| Capacitor | An electronic component that can store and maintain an electrical charge for a period of time, releasing it cleanly and evenly. Capacitors are used to smooth out the flow of electricity. |
| CAPS LOCK Key | A key on the left side of your keyboard. When pressed it changes all typed letters to capitals until it is pressed again. It only affects letters; not punctuation, symbols or numbers. |
| Card | Refers to a printed circuit board (adapter board or expansion card) that installs into one of the expansion slots in your computer, expanding the capabilities of your system, allowing it to communicate with external devices such as monitors or speakers. |
| Case | The format of a letter. It can be uppercase (capitalized) or lowercase (not capitalized). |
| Case Sensitive | A program or function that differentiates between capital and non-capitalized letters or words. Something that is not case sensitive would view 'target' and 'TARGET' as the same word. A case sensitive program would see two different words. |
| Cathode Ray Tube | The display screen used in most monitors and television sets. An electron gun, at the back of the tube, shoots electrons at a phosphor coated screen, scanning from top to bottom, left to right. This causes the phosphor pixels to glow which creates the picture you see on the screen. |
| CD-R | A Compact Disk (CD) device that can write data to a CD. Once written, this data cannot be erased or written over. |
| CD-RW | A Compact Disk (CD) device that can write or record data to a CD. This CD device can then erase or write over (re-write) the data previously recorded. |
| Cell | Spreadsheets and tables can be broken up into individual columns and rows which intersect forming smaller boxes or cells. Cell C8 would be the box at the intersection of column B and row 8. These boxes can hold different formulas, text or numbers. |
| Central Processing Unit | The central processing unit (CPU) is an integrated circuit chip (IC) that controls and directs the activities of the computer. Considered the 'brain' of your computer, it is identified by manufacturer, model, and processing speed in megahertz (MHz). Major manufacturers include Intel, Motorola, Cyrix, AMD(Advanced Micro Devices), and IBM. Intel is considered to be the #1 manufacturer and sets the standards for processors. |
| Centronics Connector | Named after the company that originally developed the standard, this connector can be found on the back of many of today's printers (36 pins). It's a parallel interface that has eight data lines and lines for control and status information. It can also be found on scanners and SCSI devices (50 pins). |
| CGA | Color Graphics Adapter. One of the first color display adapter cards. It had a palette of 16 colors but could only display 4 at a resolution of 320 X 200 pixels. Even in monochrome (one color) it had poor resolution for graphics (640 X 200 pixels). |
| Chain | A chain is a group of clusters on a storage disk, linked together to contain a single file. |
| Chipset | A group of microchips that actually control the flow of information on your computer. They are the controllers for the memory, cache, hard drive, keyboard, etc.. These groups of chips direct traffic along the bus and can allow devices to talk to each other without having to go through the CPU. |
| Circuit Board | Boards used in electronic devices that are made from an insulating material and contain electronic components that are interconnected to form a circuit or group of circuits that perform a specific function. |
| Client | A computer hooked to a network, that uses data or programs that are located on another computer (server). |
| Clock Speed | The clock speed is the frequency which determines how fast devices that are connected to the system bus operate. The speed is measured in millions of cycles per second (MHz or megahertz) and is generated by a quartz crystal on the motherboard which acts as a kind of metronome. Devices that are synchronized with the clock may run faster or slower but their speed is determined by multiplying or dividing a factor by the clock speed. |
| Cluster | A cluster is made up of one or more sectors and is the smallest allocation unit that your computer can write to a disk. Cluster size (number of sectors/cluster) depends on type and size of your hard drive and the Operating System that you are using. If you write a very small file, it is still going to take up a full cluster on your hard drive. If your file is large then it will be written to a group of clusters that are linked together to form a cluster chain. |
| CMOS | Complimentary Metal-Oxide Semiconductor. This is one of two technologies used to produce or manufacture microchips. The other is TTL or Transistor Transistor Logic. Although CMOS is a little slower and much more susceptible to ESD or static electricity, it uses less power and generates a lot less heat and has replaced the bulkier chips in PCs. All of today's CPUs and memory chips are CMOS chips. Because your computer's configuration or setup is stored in a CMOS chip, it has sometimes been labeled CMOS setup, or just plain CMOS. So if someone suggests you check your CMOS, they mean you should look in your setup program. |
| COAST | Cache memory is generally hard-wired to the system board. However, you can often add to or upgrade your systems cache by inserting a cache memory module into a socket on the motherboard. These modules are called Cache On A Stick, or COAST modules. |
| Cold Boot | Starting the computer from a power-off status. If your computer is off, and you turn the switch on, you're performing a Cold Boot. |
| COM Port | See communications port. |
| COMMAND.COM | This is the command interpreter that interprets the commands received from the operator (or an application) into something the computer can understand. It can accept commands from the user, launch programs and pass this information to the computer, or the other operating system files. |
| Communications Port | Serial ports used to connect modems, serial printers and other peripherals to your computer. Each port is assigned its own individual number, IO address, and Interrupt Request Line. COM1 and COM2 are usually the physical serial ports you can see on the back of your computer (9-pin and 25-pin DB connectors). COM3 and COM4 are usually virtual communications ports for internal devices connected via the expansion slots inside your computer. |
| Compression Algorithm | A process that reduces the size of a graphics file. Sometimes, the more you compress, the less detail you have. Examples of compression algorithms include .LZW and .JPG. |
| CONFIG.SYS | A user-configurable text file, in the MS-DOS Operating System, that usually contains device drivers and system setup files. During the bootup process in MS-DOS, CONFIG.SYS is located and the external device drivers and configuration options in that file are loaded. |
| Conventional Memory | Relating to the DOS memory map, conventional memory is the memory addresses between 0 and 640K. MS Dos requires the Operating System, Vector Table, and all programs to load and run in this small amount of memory. While trying to maintain backwards compatibility with the older OS, newer programs and Operating Systems have had to deal with what is termed the 640K barrier. |
| Cookie | A file written to your hard drive that Web sites use to track visitors. When you visit a Web site, a file (cookie) may be added to your hard drive or updated to include information such as the time and date, which pages you visited, any passwords you might need for the site, and any other information you might have contributed at their request. |
| Coprocessor | A separate chip (or nowadays, a portion of the CPU) that performs a lot of the calculations and number crunching for the microprocessor, relieving the CPU of some of its work and thus enhancing the overall speed of the system. |
| Corrupted Files | Any file that has been damaged or ruined. This can happen for a variety of reasons; Program glitches, crashes, user error, power failures, power spikes, memory problems.. There are different precautions you can take to reduce the chance of corrupted files, but you will experience them. |
| CPU | See Central Processing Unit. |
| Crop | To delete unwanted portions of an image. |
| Cross-linked Clusters | Files are stored on your hard disk in chains of clusters linked together. Which clusters are used and how they are linked is stored in an index or directory called the File Allocation Table or FAT. If, through some error, the FAT shows two files using the same cluster, then they are cross-linked. |
| CRT | See Cathode Ray Tube. |