Computers: Information Technology in Perspective By Long and Long Copyright 2002 Prentice Hall, Inc. Encoding J. Holvikivi 2012

Quit OUTPUTOUTPUT Information Data PROCESSPROCESS Data vs. Information INPUTINPUT

Quit 2.3 Electronic Signals Analog Digital

Quit 2.4 Binary Digits (Bits) Only 2 states possible On Off Fiber Optic Cable } Light Pulse No Light Pulse Permanently stored on CD-ROM } Pitted Not Pitted Inside the computer’s memory (RAM) } Electronic pulse present Electronic pulse absent Permanently stored on disks } Positive magnetic field Negative magnetic field } Human readable symbols On 1 Off 0

Quit Digital Digitizing Data Analog

Quit 2.6 Encoding Systems “A” is represented by this bit pattern 1 byte= 8 bits “A” is represented by this bit pattern 1 byte= 8 bits A A Encoding

Quit 2.7 ASCII Chart 7 bits Other Systems: ANSI (8 bit) Unicode (16 bit) Hexadecimal display A is 41

Quit 2.8 Encoding Systems  ASCII American Standard Code for Information Interchange  7 bit 2 7 = 128  8 bit 2 8 = 256, including control characters  ANSI, ISO Latin-1: 8 bit codes  Unicode (IBM, Microsoft, Sun)  16 bit encoding: 2 16 =   ISO four bytes   , main frame systems   keyboards, codepages

Hexadecimal notation 2 4 =16 BinaryOctalDecimalHexadecimal ABCDEF9ABCDEF

Quit 2.10 Use of hex and octal numbers  Unix access codes  Web color codes  Unicode code values  Memory addresses  Machine language

Result AND OR NOT Logical operations