chapter 17 looking “under the hood”. 2practical pc 5 th edition chapter 17 getting started in...

Chapter 17Looking “Under the Hood”

2 Practical PC 5th Edition Chapter 17

Getting Started

• In this Chapter, you will learn:− How does a computer work− What do RAM and processing circuitry look like− How does data get into chips− Does a computer use the same code for all

types of data

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Getting Started

• In this Chapter, you will learn (continued):− How does software tie into chips, codes, and

circuits − About Hardware: Microprocessors

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How does a computer work?

• A computer works by manipulating data– Data refers to the symbols that describe people, events,

things, and ideas– A computer works with data in four ways

• Accepting input data• Processing data• Producing output data• Storing data

– Input is the data that goes into a computer

• The computer puts data into RAM (Random Access Memory), a temporary holding area for data

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How does a computer work?

• RAM holds data and tells the computer what to do• A computer’s circuitry reads data and processes it• Processing data means manipulating it in some way,

such as performing a calculation• An instruction indicates that data should be

transferred from RAM to a printer, modem, or display screen as output

• Data sent to the hard disk drive is done using a a process called “storing data”

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How does a computer work?

Input data arrives in RAM and is processed

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What do RAM and processing circuitry look like?

• RAM and processing circuitry are contained in “chips” inside PC– Chip: nickname for an integrated circuit– Integrated circuit: thin slice of silicon etched with

microscopic circuitry– Microprocessor chip: carries out most of the

processing work on PC– RAM chips: temporarily hold data– ROM chips: hold the instructions for PC to boot up

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What do RAM and processing circuitry look like?

• Chip is housed in small, black, rectangular chip carrier

• Circuit board contains electrical pathways that allow data to travel between chips

• In a typical PC, a large circuit board houses the microprocessor chip, ROM chips, and support chips

• Series of RAM chips are connected to a small circuit board called a memory module

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What do RAM and processing circuitry look like?

PC System Board

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How does data get into chips?

• PC works with data converted into code and then into electronic signals that travel through circuits on chips and circuit boards– Computer codes are based ones and zeros– Each 1 or 0 is a bit (short for binary digit)– Eight bits form a byte

• Data is coded to transmit electronically• As data is gathered, processed, stored, and

transmitted, special controller chips constantly convert it from one type of signal to another

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Does a computer use the same code for all types of data?

• Computers use different codes for different types of data– Text data: ASCII, extended ASCII, ANSI, Unicode, or EBCDIC codes– Numbers for calculations: binary number system– Bitmap images: binary color code for each dot– Recorded sound: binary number represents height of wave sample

• Codes share characteristics– Digital: converts data into a finite set of numbers– Binary: uses only 0s and 1s– Fixed length: use the same number of bits to represent each data item

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Does a computer use the same code for all types of data?

ASCII code: Digital, Binary, and Fixed Length

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How does software tie into chips, codes, and circuits?

• Software is a collection of programs or program modules containing a list of instructions– Instructions are written in a computer programming

language– Today’s programming languages use English-like words– English-like words must be converted into a machine

language of 1s and 0s

• Compiling is the process of converting English-like words into 1s and 0s – Compiling creates executable EXE files

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Hardware: Microprocessors• Microprocessor is a single integrated circuit• Microcomputer is a type of computer that uses a

microprocessor as its main processing unit, such as your PC• Most microcomputers contain x86 microprocessors

− Able to work with the x86 instruction set− Intel is the original x86 chipmaker and is still the largest− Both Intel and AMD offer chips with speeds over 3 GHz

• Clock speed is measured in megahertz (MHz) or gigahertz (GHz)− One MHz is 1 million cycles per second and one GHz is 1 billion cycles

per second− Clock speed is analogous to how fast you pedal a bike. Faster cycles

mean faster computer processing

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Hardware: Microprocessors• Several factors can affect the speed at which a microprocessor

processes instructions− Instructions per clock cycle: Processors that execute multiple

instructions per clock cycle are referred to as superscalar− Cache memory is data-holding circuitry that can be accessed faster

than RAM• Level 1 cache is on the microprocessor chip• Level 2 cache is on a separate chip

− Accelerated front side bus; fast version will move data quickly and will allow the processor to work at full capacity

• HyperTransport is a technique to accelerate the rate data travels on the front side bus

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Hardware: Microprocessors• Several factors can affect the speed at which a microprocessor

processes instructions (continued)− Extended instruction sets: some processors have this feature to speed

up certain types of processing− Multi-core architecture: multi-core processor is a single microprocessor

chip with circuitry that allows it to process more than one instruction at a time

• Benchmark test is a set of standard processing tasks that measure the performance of computer hardware and software− Microprocessor benchmark tests measure processor speed

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Hardware: Microprocessors• Benchmark tests measuring processor performance fall into

categories:− Multimedia benchmarks measure performance when processing

multimedia data− Integer benchmarks measure performance when processing words and

numbers used in word processing, presentation, spreadsheet, and database applications

− Floating-point benchmarks measure performance for numbers stored in a special “floating point” format used in 3-D graphics, computer-aided design, and many computer games

− Real-world performance benchmarks measure how well a computer executes a predefined set of tasks while running word processing, spreadsheet, and other productivity software

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Who invented the first electronic digital computer?

• What do you think?– Do you think the judge made the right decision,

despite the fact that Atanasoff never filed for a patent?

– Do you think that Zuse, instead of Atanasoff, should be declared the inventor of the first electronic digital computer?

– Do you think that the computer industry would be different today if Sperry Rand had won its patent case?

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Chapter Summary

• You should now:− Understand how a computer works− Know what RAM and processing circuitry look

like− Understand how data gets into chips− Know if a computer uses the same code for all

types of data

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Chapter Summary

• You should now be able to (continued):− Know how software ties into chips, codes, and

circuits − Understand Microprocessors