Technology in Action Alan Evans Kendall Martin Mary Anne Poatsy Twelfth Edition Copyright © 2016 Pearson Education, Inc.0

Technology in Action Technology in Focus: Under the Hood

Switches Computer system  Enormous collection of on/off switches  Combined to perform addition, subtraction, and move data around Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 2

Switches Electrical Switches Computers only understand two states  Binary language consists of two numbers: 1 or 0  Electrical switches can be switched between 1 and 0 signifying “On” and “Off” Lock  Computers contain a huge collection of electrical switches Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 3

Switches Vacuum Tubes Used as switches  Earliest generation computers  Allow or block flow of electrical current Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 4 Problems with vacuum tube switches  Take up a large amount of space  Produce heat and burn out frequently

Switches Transistors Electrical switches built of layers of materials called semiconductors  Semiconductors can be controlled to conduct or insulate Made from silicon Smaller and faster than vacuum tubes Produce less heat, can be switched quickly, and are less expensive Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 5

Switches Transistors This silicon wafer has the transistor circuitry for hundreds of devices etched on it Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 6

Switches Integrated Circuits Support huge number of transistors No more than ¼ inch in size Can fit billions of transistors CPUs are microprocessor chips Tiny regions of semiconductor material Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 7

Number Systems The Base-10 Number System ,000s place s place s place s place 6 * 1, * * * 1 Number system is organized plan for representing a number Base 10 uses 10 digits (0–9) Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 8

Number Systems The Base-2 (or Binary) Number System Base-2 or binary uses two digits (0 and 1) 2 3 8s place 2 2 4s place 2 1 2s place 2 0 1s place 1011 Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 9

Number Systems Hexadecimal Notation Used to avoid working with long strings of 1s and 0s Base-16 uses 16 digits (0–9 and A–F)  A equals 10, B equals 11, etc. Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 10

Number Systems Representing Characters: ASCII American Standard Code for Information Interchange represents each letter or character as 8-bit binary code  Each binary digit is a bit  8 binary digits (or bits) create one byte Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 11

Number Systems Representing Decimal Numbers IEEE established floating-point standard  Describes how fractional parts should be represented in binary  Uses a 32-bit system  First digit indicates whether number is positive or negative  Next 8 bits store magnitude  Remaining 23 bits store value of number Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 12

How the CPU Works Machine cycle refers to series of general steps CPU performs 1.Fetch 2.Decode 3.Execute 4.Store Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 13

How the CPU Works The Control Unit Manages switches inside CPU Remembers:  Sequence of processing stages  How switches are set for each stage With each beat of system clock  Control unit moves each switch to correct on/off setting  Performs work of that stage Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 14

How the CPU Works The System Clock Moves CPU from one stage to the next Acts as a metronome, keeping steady beat or tick  Ticks, known as the clock cycle, set the pace  Pace, known as clock speed, is measured in hertz Today’s speed is measured in gigahertz, 1 billion clock ticks per second Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 15

How the CPU Works Stage 1: The Fetch Stage Data and program instructions stored in various areas of system Program or data is moved to RAM from hard drive As instructions are needed, they are moved from RAM into registers  Storage areas located on CPU Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 16

How the CPU Works Stage 2: The Decode Stage CPU’s control unit decodes program’s instructions into commands Instruction set  Commands CPU can execute  Written in assembly language  Assembly language translated into binary code Machine language—long strings of binary code Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 17

How the CPU Works Stage 3: The Execute Stage Arithmetic logic unit (ALU)  Mathematical operations  Test comparisons of values (, =)  Logical OR, AND, and NOT operations  Word size is number of bits worked with at a time Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 18

How the CPU Works Stage 4: The Store Stage Results produced by ALU are stored in registers Instruction explains which register to use When instruction is completed, next instruction will be fetched The fetch–decode–execute–store cycle begins again Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 19

Making CPUs Even Faster Building a faster CPU is not easy Must consider time to design, manufacture, and test processor For release in 36 months, CPU must perform twice as fast as currently available Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 20

Making CPUs Even Faster Pipelining CPU works on more than one stage or instruction at a time Boosts CPU performance System clock indicates when instructions move to next process Can potentially run four times faster Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 21

Making CPUs Even Faster Pipelining Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 22

Making CPUs Even Faster Multiple Processing Efforts Many high-end server systems use large number of processors Multicore processing  Quad-core processors have four separate parallel processing paths  Six- and eight-core processors are available Parallel processing uses multiple computers to work on portion of same problem simultaneously Copyright © 2016 Pearson Education, Inc. TIF Under the Hood 23

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America. Copyright © 2016 Pearson Education, Inc.