计算机英语(Charpter1 COMPUETR AND DIGITAL BASICS)教学教材.pptVIP

How does digital data work? if we want to send a message by flashing a light, your have two states: on and off. We could use a serial of on and off to present a letter such as uppercase A. In a computer, how to represent number? Numeric data consists of numbers that might be used in arithmetic operations. Computer represents numeric data using the binary system. The binary system only has two digits, 0 and 1. Decimal Binary (Base 10) (Base 2) 0 0 1 1 2 10 3 11 4 100 5 101 6 110 7 111 8 1000 9 1001 10 1010 11 1010 1000 1111101000 How do computers present words and letters? Character data if compose of letters, symbols and numbers that are not used in arithmetic operations. ASCII ( American Standard Code for Information Interchange) requires only 7 bits for each character. For example, uppercase A as 1000001, totally 256 characters Extended ASCII use 8 bits to represent characters. e.g. Uppercase a as totally 256 characters. EBCDIC (extended Binary-coded Decimal Interchange Code) is used only by older IBM mainframe computers. Unicode uses sixteen bits and can represent up to 65000 characters. The is a big bonus that it can represents characters of other language. COMPUETR AND DIGITAL BASICS Section A All