Technology Guide 1

Hardware

What is a Computer System?

Computer hardware is composed of the following components:– Central Processing Unit (CPU)– Input devices– Output devices– Primary storage– Secondary storage– Communication devices

Computer System

Input devices: accept data and instructions and convert them to a form that the computer can understand

Output devices: present data in a form people can understand

CPU: manipulates the data and controls the tasks done by the other components

Computer System, cont’d.

Primary storage: temporarily stores data and program instructions during processing. It also stores intermediate results of the processing.

Secondary storage: stores data and programs for future use

Communication devices: provide for the flow of data from external computer networks

Computer System Diagram

Evolution of Computers

The 1st generation of computers, 1946-1956 – Used vacuum tubes to store process information

The 2nd generation of computers, 1957-1963 – Used transistors for storage and processing information

The 3rd generation of computers, 1964-1979 – Used integrated circuits for storing and processing

information Early to middle 4th generation computers, 1980-1995

– Used very large-scale integrated (VLSI) circuits to store/ process information

Evolution, cont’d.

Late 4th generation computers, 1996-Present – Use grand-scale integrated (GSI) circuits to store/

process information

5th Generation of Computers, Present– Uses massive parallel processing to process

multiple instructions simultaneously (Multi-instructions processing)

Evolution, cont’d.

ENIAC – The First Computer

How the Computer Became Small

Vacuum tube

vs.

Transistor

Integrated circuit chip

VLSI

Types of Computers

Supercomputers Massively Parallel Computers Mainframes Minicomputers Workstations Microcomputers/Personal Computers (PCs) Personal Data Assistant (PDAs) Smart Card

Supercomputers

The computers with the most processing power

Use the technology of parallel processing Trillion operations/second Simulate nukes, weather forecasting, etc. TOP 500 Supercomputers of the world

(http://www.top500.org/list)

Massively Parallel Computers

Use a large number of CPUs The processors divide the large problem into

smaller pieces and work on them independently

Mainframes

Not as powerful and generally not as expensive as supercomputers

Most often used by large corporations Recall these have dummy terminals with all

processing occurring on the ‘mainframe’ 3270 and 5250 terminal emulations JCL, COBOL, CICS are acronyms

associated with mainframe computing

Supercomputers vs. Massively Parallel Computing

Parallel Processing

A Parallel Processing System is a computer system with 2 or more CPUs– Today, some PCs have 2 to 4 processors while

some workstations have 20 or more – Processing data in parallel speeds up processing

Massively Parallel Processor (MPP) systems are systems with large numbers of processors

Network Computers and Terminals

Network Computer– ‘Thin’ computer– Desktop terminal that does not store software

programs or data permanently

Minicomputers

Also called ‘mid-range’ computers Smaller and less expensive than a

mainframe Designed to accomplish a specific task

Workstations

Based on Reduced Instruction Set Computing (RISC) architecture

Provide high-speed calculations and high-resolution graphic displays

Microcomputers

The smallest and least expensive category of general-purpose computers

Four classifications based on their size:– Desktops– Laptops– Notebooks– Palmtops

Personal Data Assistant

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– Credit Cards– SunRay from Sun Microsystems

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:– Control unit– Arithmetic-logic unit (ALU)– Primary storage (or main memory)

Arithmetic Logic Unit (ALU)

The ALU adds, subtracts, multiplies, divides, compares, and determines whether a number is positive, negative, or zero

All computer applications are achieved through these six operations.

The ALU operations are performed sequentially, based on instructions from the control unit

For these operations to be performed, the data must first be moved from the storage to the arithmetic registers in the ALU

Registers are specialized, high-speed memory areas for storing temporary results of ALU operations as well as for storing certain control information

Memory

Two categories– The Register (cache)

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

– Internal Memory Chips (primary memory) These reside outside the CPU and are slower The internal memory is used to store data just before

they are processed by the CPU

Memory Diagram

Primary Storage

Primary storage, or main memory, stores data and program statements for the CPU

It has four basic purposes:– To store data that have been input until they are transferred

to the ALU for processing– To store data and results during intermediate stages of

processing– To hold data after processing until they are transferred to an

output device– To hold program statements or instructions received from

input devices and from secondary storage

Cache Memory

Caching is a technology based on the memory subsystem of your computer. The main purpose of a cache is to accelerate your computer while keeping the price of the computer low. Caching allows you to do your computer tasks more rapidly

When using a cache, you must check the cache to see if an item is in there. If it is there, it's called a cache hit. If not, it is called a cache miss and the computer must wait for a round trip from the larger, slower memory area.

A computer is a machine in which we measure time in very small increments. When the microprocessor accesses the main memory (RAM), it does it in about 60 nanoseconds (60 billionths of a second). That's pretty fast, but it is much slower than the typical microprocessor. Microprocessors can have cycle times as short as 2 nanoseconds. So to a microprocessor, 60 nanoseconds seems like an eternity.

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:

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

address in primary storage – 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

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– The execution cycle

Random-Access Memory (RAM)

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 quickly taking over as the most widely accepted type of RAM

Microprocessor Speed

The speed of a chip depends on 4 things:– Clock Speed: Determines how many times per second the

processor performs operations (Pentium 4, 2GHz)– Word length: the number of bits that can be processed at

one time by a chip. Chips are commonly labeled as 8-bit, 16-bit, 32-bit, 64-bit, and 128-bit devices. A 64-bit chip, for example, can process 64 bits of data in a single cycle. The larger the word length, the faster the chip speed.

– Width of the buses: determines how much data can be moved at one time. The wider the data bus, the faster the chip.

– Design of the chip

Input/Output Devices (I/O)

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, cont’d.

I/O devices are classified into the following categories:– Secondary storage devices: primarily disk

and tape drives– Peripheral devices: any input/output device

that is attached to the computer

Secondary Storage

Secondary Storage: 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 diskette – Optical storage – CD– DVD

Storage Hierarchy

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.

Input Devices, cont’d.

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.

Input Devices, cont’d.

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 pre-designated 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.

Source Data Automation

Source data automation captures data in computer-readable form at the moment the data are created.

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

Output Devices

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 – 8 bits.

The two most commonly used coding schemes are: – ASCII (American National Standard Code for Information

Interchange)

– EBCDIC (Extended Binary Coded Decimal Interchange Code)

Data, cont’d.

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.

Pictures, cont’d.