BIOS
Basic Input Output System is code used when a PC first starts up. It contains
configuration information about all the Input and Output devices in the
PC so that the processor chip knows how to connect to and work with them.
BIT
This is binary digit and is the smallest piece of information a computer
uses. A bit is always in one of two states, either 0 or 1, except for
the tiny instant of time required to switch from one state to the other.
BYTE
A byte is eight bits. The data and instructions (code) that a CPU uses
are coded into bytes. For example capital letter 'A' in ASCII (PC) code
is byte 0100 0001. A lower case 'a' is byte 0110 0001.
BROWSER
Software on a computer used to request and display web pages from a Server.
CABLE MODEM
A type of modem that provides very high speed access to the Internet over
the same cable that your cable TV service uses. Rates are asymmetric.
This means that downloads are much faster than uploads. Typical download
rates are 2 to 3 Mbps and uploads are in the 500Kbs range. This is blazing
speed compared to a 56Kbps dial-up modem.
CACHE
Cache is a small fast SRAM type of memory. It prevents CPU slowdown, which
happens when the CPU has to wait on slower devices like RAM memory and
the hard drive. There are two levels of cache.
Level 1 or L1 cache is a small fast memory located on
the same chip as the CPU. When files are first requested by the CPU they
are read into the CPU from the hard drive and written into the L1 cache
at the same time. When the CPU needs data again it checks the L1 cache
and if it finds it there it gets it instantly. If not, it looks successively
in the L2 cache, RAM and finally the hard drive, each of which is a little
slower in delivering the data the CPU has requested.
If the CPU finds the data it wants in a cache it's called
a 'hit' and that's good. If it doesn't it's called a 'miss' which makes
the CPU wait a little longer to get the data or instruction it needs from
one of the other slower devices.
This little bit of time saved by cache hits may not seem
significant, but keep in mind that millions of accesses can be performed
in a second. Every cache hit shaves time off the data access. Every cache
miss adds time to the access. Cache misses lower performance and cache
hits raise it!
Because level 2 or L2 cache is located in chips on the
motherboard or on the board that holds the CPU it takes a little longer
to access than the L1 cache.
L2 cache is becoming more important as it grows in size
and performance. The L1 cache is very small because it is on the same
chip as the large CPU. Due to it's small size, chances are high that the
CPU won't find the data it needs there. An L1 cache miss causes the CPU
to look in the L2 cache for the data.
The long and short of all this - If the data the CPU needs
is not found in the L1 cache or L2 cache, the CPU must to wait to get
it from the RAM memory. And if it isn't in RAM, then the CPU goes on vacation
for a number of milliseconds, which is a long time in the CPU world, while
the data is retrieved from the hard drive.
CDD
Compact Disk Drive is a storage device that uses optics to read data from
compact disks. CDDs that can read as well as write are very popular now.
CPU
The Central Processing Unit is a special chip that controls what happens
in a PC. It fetches instructions and does high speed computations on data.
It is somewhat like our brain in that it controls everything we do.
DIMM
Dual Inline Memory Module is a small printed circuit board that contains
DRAM memory chips. When we say a PC has 256 MBytes of memory we are talking
about the total capacity of all the DIMM modules installed in it.
Modern motherboard provide two to four sockets that accept DIMMs.
DOMAIN NAME
A unique name, formed with letters and numbers, that points to the actual
numerical Internet address which locates a particular computer connected
to the Internet. For instance, The Yahoo domain name points to Internet
address 66.218.71.198.
So when you enter www.yahoo.com in your browser and click
go, a special server called a domain name server intercepts and directs
your request to the server located at address 66.218.71.198.
DRAM
Dynamic Random Access Memory is type of memory that must constantly be
refreshed to retain it contents. It is used as the main memory in a PC
and is packaged in DIMMs which plug into the motherboard.
DSL Modem
DSL stands Digital Subscriber Line. The DSL modem is a fairly new device,
which allows high speed data to move between your PC and the telephone
company on the same line that you use for your telephone calls. Yes. you
can use your PC and talk over this line at the same time without interference!
How? Picture of a double-decker bridge with two levels.
The traffic on the two levels does not interfere with each other even
though it is the same bridge, right? Think of your phone call using the
lower level and your PC using the upper level. Instead of being separated
by different levels in space, the separation is done by your PC and voice
each using a different carrier frequency, just like two different radio
stations.
FAT16
FAT is the abbreviation for File Allocation Table. It is a table where
the system keeps basic information for each file on your hard drive. The
16 indicates the number of bits used to address the hard drive. The largest
partition FAT16 can access is 2MB. When used on a hard drive that is bigger
than 2MB the drive space will be divided into a number of partitions.
For example a 10MB drive would be divided into five partitions
of 2MB each. If the drive were the only one in the system the partitions
would be called C:, D:, E:, F:, and G:.
FAT32
FAT is the abbreviation for File Allocation Table. It is a table where
the system keeps basic information for each file on your hard drive. The
32 indicates the number of bits used to address the hard drive. The largest
partition FAT32 can access is 2 Terabytes (two trillion bytes)! So far
there are no hard drives I know of that begin to approach this size. Windows
98 was the first of the Windows OS to support this file structure.
FDD
Floppy Disk Drive is a device which provides a way for the PC to read
and write floppy disks, which are a type of removable storage media. Floppy
disks (3 1/2 inch) have a capacity of 1.44 Mbytes. When PCs first came
out, floppy disks were 5 1/4 inch and held 720 Kbytes.
FIREWALL
Software to protect computers against hackers.
FIREWIRE
Firewire also known as IEEE 1394 or iLink is a very fast serial bus that
runs at 400 Mbps. It competes directly against USB 2.0. Transmit and Receive
data are carried on two separately-shielded twisted pair transmission
lines. There are two other, rarely used, wires that provide power to remote
devices.
Many newer computers have Firewire ports that are used to connect them
to very fast external devices.
FTP
File Transfer Protocol is the method used by computers to send and receive
files over the Internet.
HTML
Hyper Text Markup Language is the coding that is used to format web pages
on Servers so that Browsers can display them.
HTTP
Hyper Text Transport Protocol is used by browsers and servers to facilitate
the transport of web pages across the Internet.
HDD
Hard Disk Drive is a device that provides a large fixed typically (non
removable) storage area. Some units today easily removable from the front
of the PC. The capacity of HDDs has continued to increase. 40Gbyte drives
are readily available and inexpensive. The HDDs used in the first PC had
only 10Mbytes of storage.
IDE
Integrated Drive Electronics refers to the electronic control section
of a Hard or Floppy Drive. This control section coordinates the electromechanical
operation of the drive so that data can be written to and read from the
spinning disk inside it. The motherboard connects to Drives over an IDE
ribbon cable.
I/O
This means Input/Output. Input is data or signals that are fed into a
device. Output is data or signals that a device drives to the outside.
Some devices can do both, others are only one or the other.
ISA
Industry Standard Architecture refers to a type of expansion slot on the
motherboard. It is the oldest of all expansion type slots and first appeared
in the IBM PC XT. Thousands of expansion or add-on cards as they are also
called, have been designed to plug into the ISA slot. The use of expansion
cards vastly extends the function and capability of the PC.
KEYLOGGING
Software/hardware to track keystrokes on a computer to gather passwords,
credit card numbers.
MEMORY NON-VOLATILE
Memory is a device that retains information electronically. When power
is removed the information is retained.
MEMORY VOLATILE
Memory is a device that retains information electronically. When power
is removed the information is lost. The DRAM memory used in a PC is the
volatile type.
OS
Operating Systems are the basic foundation or platform programs that allow
you to load and run other programs on a PC. Windows 95 is an example of
an Operating System.
PARALLEL PORT
The parallel port is a standard port on a PC and moves data out of the
PC. One byte (eight bits in parallel) are sent out on 8 pins for each
data transfer. Historically this port is connected to your printer. It
also known as a 'Centronics' port, named after the manufacturer of the
38- pin connector first used on the parallel port.
PCI
Peripheral Component Interconnect refers to a type of expansion slot found
on PC motherboards. It is a newer type of expansion slot than ISA, and
many types of Add-On cards have been designed to use it.
RANDOM ACCESS
This refers to an access method. It means that any random location in
a storage or memory device can be immediately accessed, with out going
serially to get there. It's like a cassette where your at the beginning
and have to wind through everything on the tape to get to the last song!
Compact Disks and PC Main memory are random access devices.
SERIAL ACCESS
This access method is found in audio or video cassettes. It means you
can not access any location you choose to instantly. You might have to
rewind or fast forward through lots of information you are not interested
in to get to where you want to go.
SERIAL PORT
The serial port is standard port on a PC and can move data in and out
of the PC. The serial port moves one bit on each data transfer. Many different
types of devices connect to a PC through it.
SERVER
Software on a computer that serves web pages in response to requests from
a Browser.
SIMM
Single Inline Memory Module is a small printed circuit board that contains
DRAM memory. This is an older board style that was used in PCs before
DIMMs were developed.
SPAM
Unsolicited e-mails and pop-ups, often offering products or services in
which you have no interest.
SPYWARE
Small programs that secretly monitor sites visited, potentially violating
privacy and slowing computers.
SRAM
Static Random Access Memory is type of memory that retains data without
being refreshed. It is used in the cache memories of the PC.
TROJAN HORSE
Trojan horses are dangerous programs that appear like they might perform
some useful task, or provide entertainment. This false appearance encourages
people to run them. When they are run, they can damage files or place
a virus on your computer.
Unlike a virus a Trojan horse does not replicate and spread.
Since it isn't a virus it can't be repaired and must be erased from your
computer.
USB
Universal Serial Bus is a high speed serial bus found on all newer PCs.
Eventually it will obsolete the serial and parallel ports still found
on most PCs.
USB specifies three data rates. Every USB port may not
support the highest rate. If you buy a device with a USB port, make sure
out find out which rates it does support.
Low speed - 1.5Mb/s
Full Speed - 12Mb/s
High Speed - 480 Mb/s
VIDEO ADAPTER
The video adapter is circuit board found in the PC or monitor that controls
how data is converted and sent to the monitor for viewing.
Most displays and video adapters adhere to the Video Graphics
Array (VGA) standard, which describes how data - the red, green, blue
data streams - are passed from the computer to the display.
In addition, it defines the frame refresh rates in hertz
and the number and width of horizontal lines, which in turn identifies
the screen resolution in pixels.
Here are some of the video standards that
have been used:
CGA is 320 x 200 - developed in 1981 by IBM, no longer in use.
EGA is 640 x 350 - developed in 1984 by IBM, no longer in use.
VGA is 640 x 480 - developed in 1987 by IBM and still in use.
Super VGA is 800 x 600.
Extended Graphics Adapter, XGA is 1024 x 768.
Super XGA is 1280 x 1024.
Ultra XGA is 1600 x 1200.
VIRUS
It is a program designed to change the way your computer operates without
your permission or knowledge. When a virus attaches itself to another
file, it infects it. Any time you activate an infected file it can damage
files, cause erratic system behavior, or display messages. Some system
viruses are programmed specifically to corrupt programs, delete files,
or erase your disk.
Viruses are inactive until you run an infected program,
start your computer from a disk with infected system files, or open an
infected file. Once a virus is active in memory it can infect any other
programs, local or network, that you run.
Files infected with a virus can be inoculated (the virus
is removed from the program).
