Computing Components

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Computer Components

• Consider the following ad

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Sizes in Perspective

• Admiral Grace Murray Hopper – A coil of wire nearly 1,000 feet long

• Distance traveled by an electron along the wire in the space of a microsecond

– A short piece of wire• In the space of a nanosecond

– A bag containing grains of pepper• In the space of a picosecond

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Sizes in Perspective

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History of Computers

Abacus invented in Babylonia in 3000BC

Adding machine by Blaise Pascal (1642)

Difference engine and the analytical engine by Charles Babbage (1842)

IBM first electromechanical computer (using relays) designed by Howard Aiken (1937) was based on punched cards. used to calculate tables of mathematical functions

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History of Computers

1st Generation Computers (1940s to early 1950s) – based on vacuum tubes technology. 1943 – ENIAC: first fully electronic computer, designed by

John Mauchly 1944 – Mark I: Howard Aiken 1946 – EDVAC: first stored program computers, designed by

John von Neumann

2nd Generation Computers (late 50s to early 60s) – based on transistors technology. more reliable, less expensive, low heat dissipation IBM 7000 series, DEC PDP-1

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History of Computers

3rd Generation Computers (late 60s to early 80s) – integrated circuits (IC). IBM 360 series, DEC PDP-8 IC – many transistors packed into single container

low prices, high packing density

4th Generation Computers (present day) LSI/VLSI small size, low-cost, large memory, ultra-fast PCs to

supercomputers

5th Generation Computers (future) massively parallel, large knowledge bases, intelligent Japan, Europe and US advanced research programs

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History of Computers

Web sites History of Computers

(http://www.comp.nus.edu.sg/~sf100/c1f7.htm) ACM Timeline of Computing History

(http://www.computer.org/computer/timeline) The Virtual Museum of Computing

(http://www.comlab.ox.ac.uk/archive/other/museums/computing.html)

IEEE Annals of the History of Computing (http://www.computer.org/annals/)

and others (surf the web)

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Application Areas

Scientific: weather forecasting, simulation, space-program. one of the earliest application areas. heavy computation but small amount of data.

Commercial: accounting, banking, inventory, sales. changes nature of business – information is money. high data throughput, simple calculations.

Manufacturing: numerical control, CAD/CAM, integration. graphics, interfacing, device-drivers, networks.

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Application Areas

Real-time & Control System: air-traffic control, aircraft,nuclear power station. real time, very fast, safety-critical.

Educational & Recreational CAI software, multi-media, games, Internet, World Wide

Web.

Telecommunication Network, SCV, Singapore One.

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Types of Computers

Supercomputers: very fast (Gflops) but expensive machine($10m), vector or

parallel processors, used in scientific applications and simulations.

Mainframes: fast (>10mips) but expensive ($1m), high-throughput, used

in large commercial organisations, support many concurrent users interactively.

Mini-computers: fast but affordable ($200k), used in medium-sized

organisations (e.g. SoC), support multiple users.

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Types of Computers

Workstations: affordable ($20k) and fast single-user systems (20 riscs

mips), good graphics capabilities, engineering, network-based computing.

Micro/Personal/Home Computers: cheap and affordable ($3k), transportable, home use, good

for games and as educational tool, word processing, suitable for small enterprise.

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Computer Configurations

Stand-alone computer system

Modem connection

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Computer Configurations

Terminals-host connections

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Computer Configurations

Network of computers

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Computers as Information Processors

Example: An automobile augments our power of locomotion.

A computer is a device capable of solving problems according to designed program. It simply augments our power of storage and speed of calculation.

Driver

Programmer

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Computers as Information Processors

Unlike previous inventions, computers are special because they are general-purpose. Could be used to perform a variety of tasks.

Computer = Hardware + Software. Hardware: physical components for computation/processing;

should be simple, fast, reliable. Software: set of instructions to perform tasks to

specifications; should be flexible, user-friendly, sophisticated.

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Computer as Information Processors

Computer are Information Processors

Data Units: 1 bit (binary digit): one of two values (0 or 1) 1 byte: 8-bits 1 word: 1, 2, or 4 bytes, or more (depends on ALU)

Computer system

Raw data

Processed information

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Basic Machine Hardware Architecture

Main Components: CPU (Central Processing Unit: controls devices and

processes data). Memory: stores programs and intermediate data. Input Devices: accept data from outside world. Output Devices: presents data to the outside world.

An analogy with Human Information Processors: CPU – brain’s reasoning powers Memory – brain’s memory Input Devices – eyes, ears, sensory sub-system Output Devices – mouth, hands, facial and body expressions

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Basic Machine Hardware Architecture

Monitor (Output)

Mouse and Keyboard (Input)

Headphone (Output)

Hardware box (has processor, memory, buses etc.)

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Basic Machine Hardware Architecture

Motherboard (Printed Circuit Board)

Processor

Slots for RAM chips

Network card and CRT card

Cage for mounting drives

Floppy disk drive and Hard disk drive

© above picture: Patterson and Hennessy

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Stored-Program Concept

Figure 5.1 The von Neumann architecture

Memory

• Memory is a collection of cells, each with a unique physical address

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Arithmetic/Logic Unit

• Performing basic arithmetic operations such as adding

• Performing logical operations such as AND, OR, and NOT

• Most modern ALUs have a small amount of special storage units called registers

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Input/Output Units

• An input unit is a device through which data and programs from the outside world are entered into the computer– Keyboard, the mouse, and scanning devices

• An output unit is a device through which results stored in the computer memory are made available to the outside world– Printers and video display terminals

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Control Unit

• Control unit is the organizing force in the computer

• There are two registers in the control unit– The instruction register (IR) contains the

instruction that is being executed– The program counter (PC) contains the

address of the next instruction to be executed

• ALU and the control unit called the Central Processing Unit, or CPU

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Flow of Information

• The parts are connected to one another by a collection of wires called a bus

Figure 5.2 Data flow through a von Neumann architecture

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The Fetch-Execute Cycle

• Fetch the next instruction

• Decode the instruction

• Get data if needed

• Execute the instruction

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Figure 5.3 The Fetch-Execute Cycle

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RAM and ROM

• RAM stands for Random Access Memory– Inherent in the idea of being able to access each

location is the ability to change the contents of each location

• ROM stands for Read Only Memory– The contents in locations in ROM cannot be changed

• RAM is volatile, ROM is not– This means that RAM does not retain its bit

configuration when the power is turned off, but ROM does

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Secondary Storage Devices

• Because most of main memory is volatile and limited, it is essential that there be other types of storage devices where programs and data can be stored when they are no longer being processed

• Secondary storage devices can be installed within the computer box at the factory or added later as needed

Magnetic Tape

• The first truly mass auxiliary storage device was the magnetic tape drive

Figure 5.4 A magnetic tape

Magnetic Disks

• A read/write head travels across a spinning magnetic disk, retrieving or recording data

Figure 5.5 The organization of a magnetic disk

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Compact Disks

• A CD drive uses a laser to read information stored optically on a plastic disk

• CD-ROM is Read-Only Memory

• DVD stands for Digital Versatile Disk

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Synchronous processing

• One approach to parallelism is to have multiple processors apply the same program to multiple data sets

Figure 5.6 Processors in a synchronous computing environment

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Pipelining

• Arranges processors in tandem, where each processor contributes one part to an overall computation

Figure 5.7 Processors in a pipeline

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Ethical Issues: Facial Recognition/Privacy

• An identity verification technique that matches the structure of a person’s face to his/her picture– Cameras scan the peaks and valleys of features

• An invasion of privacy?– Critics oppose both clandestine capture (the scanning

of faces without consent) and tracking (the use of this technology to monitor a person’s movement)