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Unless the instructions and data are saved to a disk, RAM forgets them when you turn
your computer off. RAM is measured in megabytes (M). Most computers today come
with 32M of RAM, though some sell with only 16M installed. There are a few different
flavors and speeds of RAM, as well. One of the most prominent today is Extended Data
Output (EDO) RAM, but an even faster type of RAM that has just hit the market is called
SyncDRAM
.
Serial port –
Serial ports are also sometimes called
COM
(short for COMmunications)
ports, and are labeled
COM1
,
COM2
, and so on. It is simple in concept: one line to send
data, another line to receive data, and a few other lines to regulate how data is sent over
the other two lines – from commonplace modems and printers to plotters and burglar
alarms. The most common use for serial port is with a
mouse
or
modem
. The reason
for this is that a serial port is not a very efficient way to transfer data, so little data that
speed is not crucial, and perfect for modems because with current technology, phone lines
cannot transport more than one signal at a time anyway. The
serial port
is often referred
to as an
RS-232 port
.
SCSI (Small Computer System Interface) – An intelligent bus for transmitting data
commands between a variety of devices. There are many implementations of SCSI,
including Fast SCSI, Wide SCSI, Fast Wide SCSI, Fast-20, and Fast-40.
SCSI-2 – The second generation of SCSI; includes many improvements to SCSI-1,
including Fast SCSI, Wide SCSI, and mandatory parity checking.
SCSI-3 – The third generation of SCSI; introduces Fast-20 and Fast-40 as
improvements to the parallel bus. The standard also includes a number of specifications
for high-speed serial bus architectures such as SSA, Fiber Channel, and IEEE 1394.
Also known as Ultra SCSI.
Ultra SCSI – Also known as SCSI-3, is a third generation SCSI standard that introduced
parallel bus speed improvements (FAST-20 and FAST-40), an the miniaturized 68-pin
micro connector.
USB (Universal Serial Bus) – USB consolidates serial, parallel, keyboard, mouse, and
game ports into one asynchronous and isochronous communications port with bandwidth
for data transfer speeds up to 12 Mbps without termination. By daisy-chaining USB hubs,
up to 127 I/O devices can be connected to one USB port on the PC. USB is completely
plug-and play meaning peripherals can be correctly detected and configured automatically
as soon as they are connected.
UTP (Unshielded Twisted Pair) – Twisted pair cable with neither individual nor overall