Binary number system = A method of representing numbers in which only the digits 0 and 1 are used. Successive units are powers of 2 such as 23=8; 28=256. In our normal day life we use the Arabic number system which uses the base 10 and successive units are powers of 10 such as 102=100; 104=10,000; etc.
Bit = the smallest unit of information storage capacity found in a computer; we treat a bit as either the binary 0 or 1. The term bit is derived from the blend of B(INARY) and (DIG)IT. The bit is physically a transistor or capacitor in a memory cell, a magnetic domain on disk or tape, a reflective spot on optical media or a high or low voltage pulsing through a circuit.
Byte = (BinarY TablE) The common unit of computer storage from micro to mainframe. It is made up of eight binary digits (bits). A byte holds the equivalent of a single character, such as the letter A, a dollar sign or decimal point. For numbers, a byte can hold a single decimal digit (0 to 9), two numeric digits (packed decimal) or a number from 0 to 255 (binary numbers).
American Standard Code for Information Interchange (ASCII) = Pronounced "ask-ee." A binary code for text as well as communications and printer control. It is used for most communications and is the built-in character code in most minicomputers and all personal computers. ASCII is a 7-bit code providing 128 character combinations, the first 32 of which are control characters. Since the common storage unit is an 8-bit byte (256 combinations) and ASCII uses only 7 bits, the extra bit is used differently depending on the computer.
Unicode = A superset of the ASCII character set that uses two bytes for each character rather than one and is therefore a 16-bit code. Unicode is able to handle 65,536 character combinations rather than just 128 that ASCII can handle.
Operating System = The software in a computer that supports a computer's basic functions, such as scheduling tasks, executing applications and controlling peripherals, such as the keyboard, mouse, monitor, and printer.
Application = A program or piece of software designed and written to fulfill a particular purpose of the computer user.
Quantity
Byte = 8 bits
Kilobytes (KB) = 1,000 bytes = 103 bytes
Megabytes (MB) = 1,000,000 bytes = 106 bytes
Gigabytes (GB) = 1,000,000,000 bytes = 109 bytes
Terabytes (TB) = 1,000,000,000,000 bytes = 1012 bytes
Speed
Basically electrons that move about in a computer carrying information
move at the speed of light. The speed of light = 186,000 miles per
second. The circumference of the earth is approximately 25,000 miles.
Therefore an electron could move almost 7.5 times around the earth in
one second.
Second (sec) = the amount of time to say "one one thousand"
Millisecond (ms) = one thousandth of a second = 10-3
second
Microsecond (µs) = one millionth of a second = 10-6
second
Nanosecond (ns) = one billionth of a second = 10-9 second
(in this amount of time an electron can only move approximately 1 foot)
Picosecond (ps) = one trillionth of a second = 10-12
second
CPU = Central Processing Unit. Every computer has at least one. Our computers only have one CPU.
RAM = Random Access Memory. Our computers have 256MB of main memory. This is very fast memory and consequently very expensive relative to other storage medium. Time to access data on in RAM is generally measured in nanoseconds (approximately 10 ns).
Hard Drive = The main storage medium on all computers today. The computers in Room 226 have 40 GB of storage. Time to access data on a hard drive is generally measured in milliseconds (approximately 20 ms). So as you can see it is about 2 million times faster to get something out of RAM vs getting it off the hard drive, which is so much slower.
ROM = (Read Only Memory) A memory chip that permanently stores instructions and data. Its contents are created at the time of manufacture and cannot be altered. ROM chips are used to store control routines in personal computers (ROM BIOS), peripheral controllers and other electronic equipment. When computers are used in handheld instruments, appliances, automobiles and any other such devices, the instructions for their routines are generally stored in ROM.
Compact Disc = Com·pact Disc (CD) are used to store information such as: hi-fi stereo sound, text, video or graphic images. It is digitally encoded in a format readable by laser beam. CDs can hold 650MB of data, which is equivalent to about 250,000 pages of text or 20,000 medium-resolution images. CDs are becoming obsolete and are being replaced with DVDs on new computers.
Digital Video Disc = Digital Video Disc (DVD) is a type of high-capacity optical compact disc that can store a much larger quantity of hi-fi stereo sound, text, video or graphic images than can a conventional compact disc (CD). It is digitally encoded in a format readable by laser beam. Today DVD discs have a capacity of 4.7 GB. In time DVDs will completely replace CD discs since they hold so much more data and are backward compatible with the CD discs. DVD disc drives can read DVD discs as well as CD discs. Eventually a double-sided double density DVD will have a capacity of 17 GB.
Bus = A parallel circuit (generally will be 32 bits wide in our computers) that connects the major components of a computer, allowing the transfer of electric impulses from one connected component to any other. You can think of a computer bus as being an interstate highway with 32 lanes. In each lane is a car carrying one bit. All cars carry their bits down the bus to their destination, which will be a register, where all the bits are deposited and then the bus brings another group of 32 bits to their destination.
USB = Universal Serial Bus. The speed of a USB 1 bus is 12 Mbps (million bits per second) and the USB 2 bus is 400 Mbps. These buses can accommodate up to 127 devices connected to the same bus. The USB port is used to attach such things as keyboards, printers, cameras, etc. Notice that sometimes we use bits to describe speed and other times we use bytes – be careful about this.
FireWire = A high-speed serial bus developed by Apple and Texas Instruments that allows for the connection of up to 63 devices. Also known as the IEEE 1394 standard, the iLink connector and the High Performance Software Bus (HPSB). Firewire can move data at 400 Mbps transfer rates. Newer versions of Firewire can move data at 800 Mbps speeds. FireWire supports hot swapping, multiple speeds on the same bus and isochronous data transfer, which guarantees bandwidth for multimedia operations. It is widely used for attaching digital camcorders and other video devices to the computer.
Gigahertz (GHz) = One billion cycles per second. Generally this is the term that is used to describe how fast the computer is running. The computers in Room 226 are running at 2.79 GHz. Caution - speed of a computer is affected by many attributes of which the Gigahertz is only one attribute.
Cache = Pronounced "cash." A fast storage buffer in the computer. It can be referred to as the cache memory, which works in conjunction with RAM. Our best computers have 1 MB of cache memory. Additionally it can be referred to as software caching such as the caching of web pages that takes place with Internet browsers.
Modem = A device that converts data from one form into another, as from one form usable in data processing to another form usable in telephonic transmission. Modem is a blend of MO(DULATOR) + DEM(ODULATOR).
Boot = When we "boot" a computer we start the computer up. The term comes from the word bootstrap (A loop of leather, cloth, or synthetic material that is sewn at the side or the top rear of a boot to help in pulling the boot on.). When used in a computer science sense if I tell you to "boot" your computer I simply mean to start it up.
Storage capacity of a floppy disk = 1.44 MB. Floppy disks are obsolete and generally speaking new computers will not have a floppy disk.