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Hardware

Technology Technology Guide 1Guide 1

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What is a Computer System Computer hardware is composed of the following

components: Central processing unit (CPU) Input devices Output devicesPrimary storageSecondary storage Communication devices

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Computer System

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Representing Data Today’s computers are based on integrated circuits (chips), each

of which include millions of subminiature transistors. The “on-off” states of the transistors are used to establish a

binary 1 or 0 for storing one binary digit, or bit. A byte is a sufficient number of bits to represent specific

characters— usually 8 bits. The two most commonly used coding schemes are:

1. ASCII (American National Standard Code for Information Interchange)

2. EBCDIC (Extended Binary Coded Decimal Interchange Code)

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Representing Pictures

Pictures are represented by a grid overlay of the picture. The computer measures the

color (or light level) of each cell of the grid. The unit measurement of this is called a pixel.

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Representing Time

Time is represented in fractions of a second. The following are common measures of time: Millisecond 1/1000 seconds Microsecond 1/1,000,000 seconds

Size is measured by the number of bytes. Common measures of size are: Kilobyte 1,000 bytes (actually 1024) Megabyte 1,000 kilobytes 106 bytes

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Evolution of Computers The first generation of computers, 1946–1956

Used vacuum tubes to store process information

The second generation of computers, 1957–1963 Used transistors for storage and processing information

Third-generation of computers, 1964–1979 Used integrated circuits for storing and processing information

Early to middle fourth-generation computers, 1980–1995 Used very large-scale integrated (VLSI) circuits to store/ process

information

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Evolution of Computers (cont.)

Late fourth-generation computers, 1996–present Use grand-scale integrated (GSI) circuits to store/ process

information

Fifth Generation of Computers, Present Uses massively parallel processing to process multiple instructions

simultaneously Future Generations of computers

DNA Computers Optical Computers

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Types of Computers Supercomputers

The computers with the most processing power Use the technology of parallel processing

Massively parallel computers Uses a large number of processors The processors divide up and independently work on small chunks

of a large problem Mainframes

Not as powerful and generally not as expensive as supercomputers Most often used by large corporations

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Types of Computers (cont.) Minicomputers (midrange computers)

Smaller and less expensive than mainframe computers Designed to accomplish specific tasks

Workstations Based on RISC (reduced instruction set computing) architecture Provide high-speed calculations and high-resolution graphic displays

Microcomputers (micros or personal computers, PCs) The smallest and least expensive category of general-purpose computers Four classifications based on their size:

– Desktops - Note books– Laptops - Palmtops

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Types of Computers (cont.) Personal digital assistant (PDA)

A palmtop computer that combines a fast processor with a multitasking operating system

Smart Card An even smaller form of computer that has resulted from the continuing

shrinkage of integrated circuits Uses for smart cards are appearing rapidly and include;

– Checkbooks– a bank ATM that can “deposit money” into the card’s memory for

“withdrawal” at retail stores – transporting data between computers

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Network Computers & Terminals

Network computer (NC) “thin” computer desktop terminal that does not

store software programs or data permanently

Windows-based terminals (WBTs) subset of the Network

computer reduces maintenance &

support costs

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Central Processing Unit

The central processing unit (CPU) is also referred to as a microprocessor because of its small size.

The CPU is the center of all computer-processing activities, where all processing is controlled, data are manipulated, arithmetic computations are performed, and logical comparisons are made.

The CPU consists of the;1. Control unit2. Arithmetic-logic unit (ALU)3. Primary storage (or main memory)

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Primary Storage

1. To store data that have been input until they are transferred to the ALU for processing.

2. To store data that have been input until they are transferred to the ALU for processing.

3. To hold data after processing until they are transferred to an output device.

4. To hold program statements or instructions received from input devices and from secondary storage.

Primary storage, or main memory, stores data and program statements for the CPU. It has four basic purposes.

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Buses A bus is a channel (or shared data path) through which data is

passed in electronic form. Three types of buses link the CPU, primary storage, and the

other devices in the computer system.

1. The data bus moves data to and from primary storage. 2. The address bus transmits signals for locating a given

address in primary storage. 3. The control bus transmits signals specifying whether to “read”

or “write” data to or from a given primary storage address, input device, or output device.

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Control Unit The control unit reads

instructions and directs the other components of the computer system to perform the functions required by the program.

The control unit does not actually change or create data; it merely directs the data flow within the CPU.

The Machine cycle is the series of operations required to process a single machine instruction.

Each machine cycle consists of the; instruction cycle, and theexecution cycle

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Memory

There are two categories of memory: 1. The register This is part of the CPU and is very fast. It allows for the fast storage and retrieval of data and

instructions during the processing.

2. Internal memory chips These reside outside the CPU and are slower. The internal memory is used to store data just before they are

processed by the CPU.

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Random-Access Memory

Random-access memory (RAM) is the place in which the CPU stores the instructions and data it is processing. The advantage of RAM is that it is very fast in storing and retrieving

any type of data.

Dynamic random access memories (DRAMs) are the most widely used RAM chips.

Synchronous DRAM (SDRAM) is a relatively new and different kind of RAM.

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Read-Only Memory

Read-only memory (ROM) is that portion of primary storage that cannot be changed or erased.

Programmable read-only memory (PROM) is a memory chip on which a program can be stored.

Erasable programmable read-only memory (EPROM) is a special type of PROM that can be erased by exposing it to ultraviolet light.

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Microprocessor Speed

The speed of a chip depends on four things:

Clock speed Word length Data bus width Design of the chip

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Parallel Processing

A Parallel Processing System is a computer system with two or more processors.

Today, some PCs have 2 to 4 processors while workstations have 20 or more.

Processing data in parallel speeds up processing.

Massively parallel processor (MPP) systems are systems with large numbers of processors.

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Microprocessor Evolution

Microprocessors have become dramatically faster, more complex, with increasing numbers of transistors embedded in the silicon wafer.

Chips are now being manufactured from gallium arsenide (GaAs), a semiconductor material inherently much faster than silicon.

Intel has incorporated MMX (multimedia extension) technology in its Pentium microprocessors. MMX improves video compression/decompression, image manipulation,

encryption, and input/output processing.

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Microprocessor Architecture Computer architecture refers to the arrangement of the components and

their interactions. It includes; the instruction set the number of the processors the structure of the internal buses the use of caches the types and arrangements of input/output (I/O) device interfaces.

An instruction set is the set of machine instructions that a processor recognizes and can execute.

Today, there are two main instruction set strategies:– Complex instruction set computer (CISC) – Reduced instruction set computer (RISC)

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Input/ Output Devices The input/output (I/O)

devices of a computer are not part of the CPU, but are channels for communicating between the external environment and the CPU. Input devices deliver data

and instructions into the computer.

Output devices provide processing results.

I/O devices are subclassified into the following categories;

Secondary storage devices:

primarily disk and tape drives

Peripheral devices: any input/output device that is attached to the computer

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Secondary Storage

Secondary Storage is separate from primary storage and the CPU, but directly connected to it. It provides the computer with vastly increased space for storing and processing large quantities of software and data.

Secondary storage media include; Magnetic tape Magnetic disk Magnetic diskette Optical storage Digital videodisk (DVD)

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Input DevicesUsers can command the computer and communicate with it by using

one or more of the following input devices.

Keyboard. The most common input device is the keyboard. The keyboard is designed like a typewriter but with many additional special keys.

Mouse. The computer mouse is a hand-held device used to point a cursor at a desired place on the screen.

Touch Screen. The user activates an object on the screen by touching it with his or her finger.

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Input Devices (cont.)

Touchpad. A touchpad or trackpad is a small, flat, rectangular pointing device that is sensitive to pressure and motion.

Light Pen. A light pen is a special device with a light-sensing mechanism, which is used to touch the screen.

Joystick. Joysticks are used primarily at workstations that can display dynamic graphics. They are also used in playing video games. The joystick moves and positions the cursor at the desired object on the screen.

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Input Devices (cont.)

Automated Teller Machines (ATMs). ATMs are interactive input/output devices that enable people to obtain cash, make deposits, transfer funds, and update their bank accounts instantly from many locations.

Electronic Form. In form interaction, the user enters data or commands into predesignated spaces (fields) in a form. The headings of the electronic form serve as a prompt for the input.

Whiteboard. A whiteboard is an area on a display screen that

multiple users can write or draw on.

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Source Data Automation Source data automation captures data in computer-readable form

at the moment the data are created.

Examples of Source Data Automation: Point-of-sale systems Optical bar-codes Code scanners Handwriting recognizers Voice recognizers Magnetic ink character readers (MICR) Digitizers Digital Cameras

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Output Devices

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Output Devices (cont.)

Monitors Impact Printers Nonimpact Printers Plotters Voice Output

The output generated by a computer can be transmitted to the user via several devices and media.

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Communications Media

Computer CRT and terminals CD-ROM Computer interactive

videodisc Digital video interactive Compact disc interactive Computer simulation

Motion image Videodisc (cassette) Motion pictures Broadcast television Teleconference/

videoconference Animation & Virtual Reality

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Communications Media (cont.)

Projected still visuals Slide & Overhead

Graphic materials Pictures Printed job aids Visual Displays

Text Printouts

Audio Tape/cassette/record Teleconference Audioconference Sound digitizing Microphone Compact disc Music