Computing Components

Computer Components Consider the following ad Page 116

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

Sizes in Perspective Page 119

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

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

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

History of Computers Web sites 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)

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.

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.

Types of Computers Supercomputers: Mainframes: Mini-computers: 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.

Types of Computers Workstations: Micro/Personal/Home Computers: 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.

Computer Configurations Stand-alone computer system Modem connection

Computer Configurations Terminals-host connections

Computer Configurations Network of computers

Computers as Information Processors Driver 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. Programmer

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.

Computer as Information Processors Computer are Information Processors Computer system Raw data Processed information 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)

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

Basic Machine Hardware Architecture Headphone (Output) Monitor (Output) Hardware box (has processor, memory, buses etc.) Mouse and Keyboard (Input)

Basic Machine Hardware Architecture Network card and CRT card Motherboard (Printed Circuit Board) Floppy disk drive and Hard disk drive Slots for RAM chips Cage for mounting drives Processor © above picture: Patterson and Hennessy

Stored-Program Concept Figure 5.1 The von Neumann architecture

Memory Memory is a collection of cells, each with a unique physical address Page 122

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

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

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

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

The Fetch-Execute Cycle Fetch the next instruction Decode the instruction Get data if needed Execute the instruction

Figure 5.3 The Fetch-Execute Cycle

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

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

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

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

Pipelining Arranges processors in tandem, where each processor contributes one part to an overall computation Figure 5.7 Processors in a pipeline

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)