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Chapter 2 Computer Hardware. Section A: Data Representation and Digital Electronics. Computer Concepts 7th Edition Parsons/Oja. Data Representation: How do computers represent data digitally?. Data is defined as the symbols that represent things, people, events and ideas

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Chapter 2 computer hardware l.jpg

Chapter 2Computer Hardware

Section A: Data Representation and Digital Electronics

Computer Concepts 7th EditionParsons/Oja


Data representation how do computers represent data digitally l.jpg
Data Representation: How do computers represent data digitally?

  • Data is defined as the symbols that represent things, people, events and ideas

  • Computers store data in digital format as a series of 1s and 0s (known as binary code)

    • Each 1 and 0 is called a bit

    • Eight bits is called a byte

  • The term bit comes from “binary digit”

  • Bytes are used to represent one character – a letter, number, or punctuation mark

    • For example, the letter H is represented in binary code as 01001000

    • An exclamation point (!) is 001000001

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Data Representation: How do computers represent data digitally?

  • Digital data is made up of discrete numbers, with each bit being either a 1 or a 0 – it’s either on or off, nowhere in between

  • Analog data is made up of a continuous wave of information, with varying degrees in between

  • For example:

    • A digital clock changes it’s digital display once every minute to show the time

    • An analog clock is continually moving it’s second, minute and hour hands to show the time

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Data Representation: How do computers represent data digitally?

  • Another example isa light fixture

    • A standard light switch is similar to digital

      • It is either on or off – 1 or 0

    • A dimmer light switch is similar to analog

      • It’s rotating dial can be turned to many different positions to make the light varying degrees of bright or dim

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Data Representation: How do computers represent data digitally?

  • Data representation makes it possible to convert letters, sounds, and images into electrical signals

  • Digital electronics makes it possible for computer to manipulate simple “on” and “off” signals to perform complex tasks

    • A computer’s circuits have only two states: on and off

    • A binary 1 represents “on”

    • A binary 0 represents “off”

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How can a computer represent numbers l.jpg
How can a computer represent numbers? digitally?

  • Unlike the decimal system (base 10), the binary number system (base 2) uses only two digits: 0 and 1

  • The following table lists some decimal numbers and their binary equivalent:

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How can a computer represent words and letters using bits l.jpg
How can a computer represent words and letters using bits? digitally?

  • Character data is composed of letters, symbols, and numbers that will not be used in arithmetic operations

    • Numeric data is used in arithmetic calculations, and is encoded differently

  • ASCII (American Standard Code for Information Interchange) requires only 7 bits for each character

  • Extended ASCII uses 8 bits for each character. Used in most personal computers

    • See the code on the next slide

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How can a computer represent words and letters using bits8 l.jpg
How can a computer represent words and letters using bits? digitally?

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How can a computer represent words and letters using bits? digitally?

  • EBCDIC (Extended Binary-Coded Decimal Interchange Code) is an alternative 8-bit used by older IBM systems

  • Unicode uses 16 bits and provides codes for 65,000 characters – a bonus for representing alphabets of multiple languages

    • Used for foreign language support

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How does a computer convert sounds and pictures into codes l.jpg
How does a computer convert sounds and pictures into codes? digitally?

  • Sounds and pictures must be transformed into a format the computer can understand

  • A computer must digitize colors, notes, and instrument sounds into 1s and 0s

  • For example, a red dot on your screen might be represented by 1100, a green dot by 1101

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How does a computer store all these codes l.jpg
How does a computer store all these codes? digitally?

  • Data is stored on a computer in a file

    • Data files might contain the text of a document, the numbers for a calculation, the contents of a web page, or the notes of a music clip as binary code

    • Executable files contain the programs or instructions that tell the computer how to perform a specific task. For example, how to display and print text

  • Data files have a file header which tells the computer how the binary code is used to represent the data.

    • The header tells the computer if the binary code represents a music file, a graphic, a text document, etc.

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Quantifying bits and bytes how can i tell the difference between bits and bytes l.jpg
Quantifying Bits and bytes: How can I tell the difference between bits and bytes?

  • A bit is one binary digit (b)

    • Eg. 0

  • A byte is 8 bits (B)

    • Eg. 0010 0100

  • A nibble is 4 bits

    • Eg. 0011

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Quantifying Bits and bytes: How can I tell the difference between bits and bytes?

  • Prefixes

    • Kilo- means a 1000

    • Mega- means million

    • Giga- means billion

  • Kilobit (Kb) is approx. 1,000 bits (1,024)

  • Kilobyte (KB) is approx. 1,000 bytes (1,024)

  • Megabyte (MB) is approx. 1,000,000 bytes (1,048,576)

  • Gigabyte (GB) is approx. 1,000,000,000 bytes (1,073,741,824)

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Self Quiz Questions between bits and bytes?

  • A(n) _______ device works with discrete numbers, whereas a(n) _______ device works with continuous data.

  • The _______ number system represents numeric data as a series of 0s and 1s.

  • Most personal computers use the _______ code to represent character data.

  • 100 Mb is larger than 100 MB. True or false?

  • A prefix that means a million bytes is _______.

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Self Quiz Answers between bits and bytes?

  • A(n) digital device works with discrete numbers, whereas a(n) analog device works with continuous data.

  • The binary number system represents numeric data as a series of 0s and 1s.

  • Most personal computers use the extended ASCII code to represent character data.

  • 100 Mb is larger than 100 MB. False

  • A prefix that means a million bytes is Mega .

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