| C: |
The designation for the primary hard disk in a
PC. The "C" evolved from the early personal computers that used A: and B: as the
labels for two floppy drives. When hard disks became available, they were named C:. Then,
for a while, A: and B: were used for the two types of floppies (3.5" and 5.25").
When the 5.25" disk was no longer used, PCs wound up with A:
and C: drives. Letters starting with D: and up are used for CD-ROMs, Zip disks, DVDs and
other removable media.
 |
|
| CAB
file |
(CABinet file) A file format from
Microsoft used to hold compressed files on its distribution disks. The Windows Extract
program is run at the DOS command line to decompress the files. For example, to view the
content of the WIN98_02.CAB file in the \WIN98 directory on the E: drive, you would use
the /d (display) switch as follows:
C:\>extract e:\win98\win98_02.cab /d
To copy and decompress EDIT.COM from that same CAB file into the current directory, you
would type:
C:\ANYWHERE>extract e:\win98\win98_02.cab edit.com |
|
| cable categories |
The following categories are based on
their transmission capacity. The majority of new wiring installations use Category 5 UTP
wire in order to be able to run or upgrade to the faster network technologies that will
require it. Categories 1 through 6 are based on the EIA/TIA-568 standard. Level 7 is
enhanced Category 5 cable is not yet standardized. See twisted
pair.
| Category |
Cable type |
Application |
| 1 |
UTP |
Analog voice |
| 2 |
UTP |
Digital voice/
1 Mbps data |
| 3 |
UTP, STP |
16 Mbps data |
| 4 |
UTP, STP |
20 Mbps data |
| 5 |
UTP, STP |
100 Mbps data |
| 5e |
UTP, STP |
500 Mbps data |
| 6 |
UTP, STP |
1000 Mbps data |
| Level 7 |
UTP, STP |
1000+ Mbps data |
|
|
| cable modem |
| A modem used to connect a computer to a cable
TV service that provides Internet access. Cable modems can dramatically increase the
bandwidth between the user's computer and the Internet service provider. Cable modems link
to the computer via Ethernet, which makes the service online all the time. However,
Ethernet is a shared medium, and the speed will vary depending on how many customers on
that cable segment are using the Web at the same time. |
|
| Cable
Select (CS) |
| A feature of some PCs that allows the hard
disks to be numerically identified by the order in which they are attached by the IDE
cable. Both the BIOS and the IDE drive must support Cable Select. Without Cable Select,
jumpers on the IDE drive must be set to Master or Slave designations. See
IDE. |
|
| cache |
Pronounced "cash." A cache is used to
speed up data transfer and may be either temporary or permanent. Memory and disk caches
are in every computer to speed up instruction execution and data retrieval. These
temporary caches serve as staging areas, and their contents can be changed in seconds or
milliseconds (see below).
Browser caches and Internet caches hold popular Web pages long periods of time and even
for the duration, because caching servers constantly update the page with the latest
version from the Internet. In these cases, the cache database is actually a folder on the
disk.
Memory Caches
A memory cache, or "CPU cache," is a memory bank that bridges
main memory and the CPU. It is faster than main memory and allows instructions to be
executed and data to be read at higher speed. Instructions and data are transferred from
main memory to the cache in blocks, using some kind of look-ahead algorithm. The more
sequential the instructions in the routine being executed or the more sequential the data
being read, the greater chance the next required item will already be in the cache,
resulting in better performance.
A level 1 (L1) cache is a memory bank built into the CPU chip. A level 2 cache (L2) is a
secondary staging area that feeds the L1 cache. Increasing the size of the L2 cache may
speed up some applications but have no effect on others. L2 may be built into the CPU
chip, reside on a separate chip in a multichip package module (see MCP)
or be a separate bank of chips. Caches are typically static RAM (SRAM),
while main memory is generally some variety of dynamic RAM (DRAM). |
|
| CardBus |
| The 32-bit version of the
PC Card (or PCMCIA Card) used for
upgrades in laptops. |
|
| carrier detect |
| A signal that indicates a connection has been
made by sensing a carrier frequency on the line. Usually referenced during a dial-up
modem connection. |
|
|
|
| CPU |
(Central Processing Unit)
The computing part of the computer. Also called the "processor," it is made up
of the control unit and ALU. Today, the CPUs of almost all computers are contained on a
single chip.
The CPU, clock and main memory make up a computer. A complete computer system requires the
addition of control units, input, output and storage devices and an operating system.
Computer professionals involved with mainframes and minicomputers often refer to the whole
computer as the CPU, in which case, CPU refers to the whole case or tower in which the
processor, memory and main components reside. |
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