2.1 Basic Knowledge of
Computer Platforms

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 Input
– Enter data into the computer
 Processing
– The computer works on the data
 Output
– The processed data or results are given out by the computer
INPUT data
PROCESSING info.
OUTPUT

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 Input devices
 Output devices
 Processing unit
 Primary storage units / Main memory
 Secondary storage units / Backing storage devices

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 Input devices are used for entering data (e.g. characters, numbers, sound, video, graphics and etc.) into the computer
 E.g., mouse, keyboard, digitizer, microphone, bar-code reader, smart card
(e.g. Octopus), scanner, Optical character recognition software, speech recognizer,
Chinese handwriting recognizer, touching screen and etc.

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 Output devices are used for displaying processed data or information (e.g. graphics & movies on screen, printouts, sound and etc.) to the users
 E.g., monitor (visual display unit), printer, speakers, plotter and etc.

 At the heart of every computer is the central processing unit (CPU), or processor, which executes program instructions and performs the computer's processing actions.
 The CPU is a collection of electronic circuits made up of thousands of transistors placed onto an integrated circuit (also called a chip or microchip).
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 The two components of the CPU are the control unit (CU) and the arithmetic/logic unit (ALU)

 it holds data only temporarily as the computer executes instructions.
 2 kinds of primary storage device:
– RAM (Random Access Memory)
– ROM (Read Only Memory)
* RAM ROM

 RAM
– memory that permits data or information to be written into or read from any memory address at any time.
– RAM stores data and information only as long as the computer is turned on ( volatile ).
 ROM
– offers random access to data, but it can hold data and information after the electric current to the computer has been turned off ( non-volatile ).
– data can be read from memory but cannot be written into it
*

*
 augments primary memory
 is used to store data over the long term or for future use.
 E.g., hard disks, floppy diskettes, magnetic tapes, CD-ROM (read-only),
CD-R (recordable), CD-RW
(rewrittable), DVD, magneto-optical
(MO) disks, zip disks, jaz disks and etc.



 contents of primary memory remain there only temporarily .
data vanishes from primary memory as soon as the computer is turned off.
Primary memory is not large enough to contain the large volume of data and information associated with business application.

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Input devices
Processing unit
Output devices
Primary storage
Secondary storage

The processing sequence is a four step processing called the machine cycle. These four steps, all of which are directed by the control unit, are as follows:
 fetch , or obtain the next instruction form memory;
 decode , or translate the instruction into individual commands that the computer can process;


 execute , or perform the actions called for in the instructions; and store , or write the results of processing to memory.
To execute the machine cycle, the control unit depends on registers, temporary storage areas in the processor.

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 Modem
– A modem modulates outgoing digital signals from a computer or other digital device to analog signals for a conventional copper twisted-pair telephone line and demodulates the incoming analog signal and converts it to a digital signal for the digital device.

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 Analog and digital signal conversion
– Digital-to-analog conversion is a process in which signals having a few (usually two) defined levels or states (digital) are converted into signals having a theoretically infinite number of states
(analog).

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 Modulation
A modem modulates outgoing digital signals from a computer or other digital device to analog signals for a conventional copper twisted-pair telephone line.
 Demodulation
A modem demodulates the incoming analog signal and converts it to a digital signal for the digital device.

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 CPU
 RAM
 Cache
 Video memory
 Display adapter

 Clock speed is one measure of computer "power," but it is not always directly proportional to the performance level.
– http://whatis.techtarget.com/definition/0,,s id9_gci211799,00.html
From whatis.com

 A bus is the path over which data are moved.
 The width of the bus determines the amount of data that can be moved at one time.

 Word size is measured in bits . A word is the number of bits a computer can process simultaneously .
 The larger the word size, the faster a computer can process data.

 The computer's workspace (physically, a collection of RAM chips). It is an important resource, since it determines the size and number of programs that can be run at the same time, as well as the amount of data that can be processed instantly.
From whatis.com

From techweb.com

 L1 and L2 are levels of cache memory in a computer.
 If the computer processor can find the data it needs for its next operation in cache memory, it will save time compared to having to get it from RAM.
From whatis.com

 L1 is "level-1" cache memory, usually built onto the microprocessor chip itself.
For example, the Intel MMX microprocessor comes with 32 thousand bytes of L1.
 L2 (that is, level-2) cache memory is built into the CPU chip or on a separate chip that can be accessed more quickly than the larger "main" memory. A popular L2 cache memory size is 1 MB.
From whatis.com

From techweb.com

 Also called "VRAM," it is a type of memory used in a display adapter. It is designed with dual ports so that it can simultaneously refresh the screen while text and images are drawn in memory. It is faster than the common dynamic RAM (DRAM) used as main memory in the computer.
From techweb.com

 An expansion board that plugs into a desktop computer that converts the images created in the computer (digital) to the electronic signals (analog) required by the monitor.
 The display adapter converts the characters or graphic patterns (bitmaps) within the computer's memory into signals used to refresh the display screen.
From techweb.com

 Display adapters also contain their own memory, which is used to build the images before they are displayed
From techweb.com

From techweb.com



Cache memory
– a form of high-speed memory that acts as a temporary holding/processing cell and eliminates the need to move data to and from the main memory repeatedly.
Co-processors
– special chips designed to handle tasks that are performed often.
By taking over this processing work from the main processor, they free the CPU to focus on general processing needs.



Accelerator boards
– are add-in circuit boards that increase a computer's processing speed.
Packing more transistors on a chip
– creating greater chip density , resulting in greater computing speed.



Reduced instruction set computing
(RISC)
– processes data more simply than complex instruction set computing. With RISC, data for the execution of an instruction are taken only from register.
This both simplifies and accelerates instruction processing.
With parallel processing
– computing handle different parts of a problem by executing instructions simultaneously .
In the end, the results of each parallel process are combined to produce a result .

*
 CD-ROM
 CD-R
 CD-RW
 DVD
 Zip
 Jaz
 Floppy diskettes
 Hard disks
From techweb.com

 ( C ompact D isc R ead O nly M emory) A compact disc format used to hold text, graphics and hi-fi stereo sound.
 It's like an audio CD with spiral, grooved tracks, but uses a different format for recording data.
 The audio CD player cannot play CD-ROMs, but CD-ROM players can play audio discs.
From techweb.com

 CD-ROMs hold 650MB of data, which is equivalent to about 250,000 pages of text or 20,000 medium-resolution images.
 The first CD-ROM drives transferred data at 150KB per second (1X) .
Speeds doubled to 300KBps (2X) and continued upward to more than 40 times (40X) the original. Access times range from 80 to 120ms.
From techweb.com

 The 120mm CD-ROM is the de facto standard for software distribution and for publishing large databases .
 The smaller mini CD-ROM is only 80mm in diameter and holds 180MB (compared to the full-size 650MB). It fits into the deeper well in the center of the tray in most
CD-ROM drives.
 CD-ROMs have a silver cast just like audio CDs.
From techweb.com

From techweb.com

 There is only one laser in a drive. Two are used here to illustrate the difference in reflection
From techweb.com

From techweb.com

From techweb.com

From techweb.com

 ( CD-R ecordable) A recordable CD-ROM technology using a disc that can be written only once .
 The drive that writes the CD-R disc is often called a "one-off machine" and can also be used as a regular CD-ROM reader.
 CD-Rs create the equivalent of pits in the disc by altering the reflectivity of a dye layer .
Different dyes can be used, including cyanine (green), pthalo-cyanine (yellow-gold) and metal-azo (blue).
From techweb.com

 Blank CD-R discs can be recorded once and read on any CD-ROM reader . CD-Rs have a gold , blue or green cast .
From techweb.com

 CD-R discs are used for beta versions and original masters of CD-ROM material as well as a means to distribute large amounts of data to a small number of recipients .
 CD-Rs are also used for archiving data . A major advantage over other media is that they can be read in most CD-ROM drives .
From techweb.com

 "Burning" your own CD-Rs is very efficient for small distributions or when it is vital to create copies immediately .
 However, when several hundred or more discs must be created , the CD-
ROM manufacturing process is generally more efficient .
 CD-ROMs are made on a pressing machine from a master plate that was derived from a CD-R recording.
From techweb.com

From techweb.com

From techweb.com

 CD-R drives such as this internal drive from
Sony look just like CD-ROM drives. Only the discs themselves look different. The underside of CD-R media typically has a greenish-gold or silver-blue cast, whereas CD-
ROMs have a silver cast.
(Image courtesy of Sony
Electronics Inc.)
From techweb.com

From techweb.com

(Image courtesy of Cedar
Technologies.)
From techweb.com

 ( CD-R e W ritable) A rewritable CD-ROM technology.
 CD-RW drives can also be used to write
CD-R discs, and they can read CD-ROMs.
 But, CD-RW disks have a lower reflectivity than CD-ROMs and CD-Rs, and newer
MultiRead CD-ROM drives are required to read them.
 Initially known as CD-E (for CD-Erasable), a
CD-RW disk can be rewritten a thousand times .
From techweb.com

 CD-RW disks can be used to master CD-
ROMs, and the same software used for CD-
R creation supports this application.
 However, unlike CD-Rs, in which the entire disc or an entire track is recorded at once,
CD-RWs support UDF (Universal Disk
Format), which is similar to the file system on a hard disk.
 Using variable packet writing, small numbers of files can be appended, and using fixed packet writing, files can be added and deleted.
 The fixed packet approach requires preformatting like a floppy disk, but takes considerably longer.
From techweb.com

 CD-RWs use phase change technology to alter the reflectivity of the disk's surface.
 Phase change is a pure optical technology and does not rely on any magnetic influence as does magneto-optic and its progeny.
 A short, high-intensity laser pulse turns a bit in the recording layer from its natural crystalline state (reflective) to an amorphous one (dull) , which does not reflect light as well.
 A medium-intensity pulse restores the crystalline structure .
 A low-intensity pulse reads the bit .
From techweb.com

From techweb.com

 DVD originally stood for Digital Video
Disc. Since the technology began to seem as important for the computer world as it did for the video world, the
"video" was dropped, and it became simply D-V-D. Later, it was dubbed
Digital Versatile Disc .
From techweb.com

 DVD is an optical disc technology that is expected to rapidly replace the CD-ROM disc (as well as the audio compact disc) over the next few years.
 A DVD holds 4.7 gigabytes of information on one of its two sides, or enough for a 133minute movie.
 With two layers on each of its two sides, it will hold up to 17 gigabytes of video, audio, or other information. (Compare this to the current CD-ROM disc of the same physical size, holding 600 megabytes. The DVD can hold more than 28 times as much information!)
From whatis.com

 DVD-Video is the usual name for the DVD format designed for full-length movies and is a box that will work with your television set.
 DVD-ROM is the name of the player that will
(sooner or later) replace your computer's
CD-ROM. It will play regular CD-ROM discs as well as DVD-ROM discs.
 DVD-R is a write-once version used for creating masters
 DVD-RAM is the writeable version.
 DVD-Audio is a player designed to replace your compact disc player.
From whatis.com and techweb.com

 DVD-Video uses MPEG-2 compression providing approximately 133 minutes of
Laser Disc-quality video per side .
 This is not a fixed length, because the compression rate is based upon the amount of motion taking place.
 DVD-Video supports Dolby Digital surround sound , which provides five discrete channels of CD-quality audio plus a subwoofer (5.1 channel).

 DVD-Audio is a second-generation digital music format that provides higher sampling rates than audio CDs. Many have welcomed the new format, believing that the original audio CD was unable to capture the total sound spectrum.

From techweb.com

From techweb.com

 At minimum, the capacity of a DVD is 750% that of a CD-ROM because its tracks, pits and lands are more than twice as dense, and it uses more efficient recording algorithms. (Image courtesy of C-Cube
Microsystems.)
From techweb.com

From techweb.com

 A 3.5" removable disk drive from Iomega.
 It uses design concepts from Iomega's
Bernoulli technology as well as hard disks to provide 100MB removable cartridges.
 The drive is bundled with software that can catalog the disks and lock the files for security.
 In late 1998, a 250MB version of the Zip drive was introduced which also reads and writes the 100MB cartridges.
From techweb.com

From techweb.com

 A high-capacity removable hard disk system from Iomega.
 The Jaz has been very popular.
 In 1997, 2GB drives were introduced, which support 1GB and 2GB cartridges
 Usually used for backup data
From techweb.com

From techweb.com

 A reusable magnetic storage medium introduced by IBM in 1971.
 The floppy was the primary method for distributing personal computer software until the mid-1990s when CD-ROMs became the preferred medium.
 The floppy disk used today is the rigid 3.5" microfloppy that holds 1.44MB
. The reason it's called a floppy is that the first varieties were housed in bendable jackets. Floppies are terribly undersized for today's use, and their future is uncertain.
From techweb.com

 Floppies spin at 300 rpm, which is from 10 to 30 times slower than a hard disk. They are also at rest until a data transfer is requested.
From techweb.com

From techweb.com

 The primary computer storage medium, which is made of one or more aluminum or glass platters, coated with a ferromagnetic material.
 Most hard disks are fixed disks, which are permanently sealed in the drive.
 Removable cartridge disks such as
Iomega's Jaz disks enable the disk to be removed from the computer and used as backup or transferred to another machine with the same drive.
From techweb.com

 Most desktop hard disks are either IDE (also known as EIDE or ATAPI) or SCSI .
 The advantage of IDE is their lower cost .
 The advantage of SCSI is that up to seven or more devices can be attached to the same controller board .
 SCSI drives are typically used in high-end servers, because SCSI is available as a fault tolerant disk subsystem ( RAID systems), while IDE drives are found in most desktop and laptop machines.
Increasingly, IDE drives are available in
RAID configurations
From techweb.com

 Hard disks provide fast retrieval because they rotate constantly at high speed, from
5,000 to 15,000 rpm . In laptops, they can be turned off when idle to preserve battery life.
 Today's hard disks start around 20 gigabytes and generally use 3.5" platters for desktop computers and 2.5" platters for notebooks .
 Hard disks are usually low-level formatted from the factory, which records the original sector identification on them.
From techweb.com

From techweb.com

(Image courtesy of Seagate Technology,
Inc.)
From techweb.com

IBM's Microdrive Introduced in late 1998 with a platter the size of a quarter, IBM's
340MB Microdrive weighs less than an AA battery.
From techweb.com

*
 bits ( bi nary digi t )


 byte = 8 bits
Kbyte (kilo byte KB ) = 1024 or 2 10 bytes
Mbyte (mega byte MB ) = 1,048,576 or 2 20 bytes
 Gbyte (giga byte GB ) = 1,073,741,842 or
2 30 bytes
 Tbyte (tera byte TB ) = 1,099,511,627,776 or
2 40 bytes

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 ( BI nary digi T ) The smallest element / unit of computer storage. It is a single digit in a binary number (0 or 1) .
 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 .
From techweb.com

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 Bits are widely used as a measurement for transmission . Ten megabits per second means that ten million pulses are transmitted per second. A 16-bit bus means that there are 16 wires transmitting the bit at the same time.
 Measurements for storage devices, such as disks, files and databases, are given in bytes rather than bits.
From techweb.com

From techweb.com

From techweb.com

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 The bit is transmitted as a pulse of high or low voltage .
 Speed is increased by making the transistors open and close faster , which is a combination of making the microscopic elements within the transistor smaller and more durable.
From techweb.com

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 Groups of bits make up storage units in the computer, called "characters,"
"bytes," or "words," which are manipulated as a group.
 The most common is the byte, made up of 8 bits and equivalent to one alphanumeric character.
From techweb.com

From techweb.com

From techweb.com

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 Making the spot or cell smaller increases the storage capacity.
 Holographic storage
From techweb.com

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 File server
 Terminal
 Workstation

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 The computer that a server program runs in is also frequently referred to as a server
From IT Teaching Kit

 A high-speed computer in a network that stores the programs and data files shared by users .
 It acts like a remote disk drive.
From techweb.com

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 In data communications, a terminal is any device that terminates one end (sender or receiver) of a communicated signal.
 In practice, it is usually applied only to the extended end points in a network, not central or intermediate devices.
 In this usage, if you can send signals to it, it's a terminal.
From IT Teaching Kit

 a terminal is an end-use device (usually with display monitor and keyboard) with little or no software of its own that relies on a mainframe or another computer (such as a
PC server) for processing.
 E.g. ATM machines
 The term is sometimes used to mean any personal computer or user workstation that is hooked up to a network.
From whatis.com

File/database server
Application server
Terminal

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 A workstation is a computer intended for individual use but faster and more capable than a personal computer.
 It's intended for business or professional use (rather than home or recreational use).
From IT Teaching Kit

 any individual personal computer location hooked up to a mainframe computer/server
 They're simply personal computers attached to a local area network (LAN) that in turn shares the resources of one or more large computers . Since they are PCs, they can also be used independently of the mainframe assuming they have their own applications installed and their own hard disk storage .
From whatis.com

 A peripheral device is any computer device that is not part of the essential computer
(the processor, memory, and data paths) but is situated relatively close by .
 A near synonym is input/output (I/O) device.
 Some peripherals are mounted in the same case with the main part of the computer as are the hard disk drive, CD-ROM drive, and
NIC.
 Other peripherals are outside the computer case, such as the printer and image scanner, attached by a wired or wireless connection.

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

Keyboards
– is the primary text input device .
It contains certain standard function keys, such as the key, tab and cursor movement keys, shift and control keys and any other manufacturercustomized keys.
Scanners
– transform written or printed information (optical character recognition scanners) or photographic images , drawings, or entire documents (image scanners) into a digital form that is entered directly into the computer.

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 Mouse
– is a small device that a computer user pushes across a desk surface in order to point to a place on a display screen and to select one or more actions to take from that position.
 Digital cameras
– capture photographic images on light-sensitive computer memory chips.
 Voice input devices
– are attached to the computer to capture spoken words and other sounds in digital form .

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

Video displays or monitors
– a monitor is a computer display and related parts packaged in a physical unit that is separate from other parts of the computer.
Printers
– which produce paper output (hard copy )

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 Plotters
– draw image information , such as charts and graphs, line drawings, and building blueprints; and
 Film recorders
– transform the electronic image on the computer screen into a film image . The uses of these devices vary greatly from business to business, but all businesses use output devices in their computer systems