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# Chapter 2 Computer Hardware - PowerPoint PPT Presentation

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 2Computer Hardware

Section A: Data Representation and Digital Electronics

Computer Concepts 7th EditionParsons/Oja

• 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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• 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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• 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 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? 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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• 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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• 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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• 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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• 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?

• 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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