tailieunhanh - Java™ How to Program ( Deitel - Deitel) - Phần 24

Tham khảo tài liệu 'java™ how to program ( deitel - deitel) - phần 24', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | PREV NEXT Page 674 continued . Data Hierarchy Ultimately a computer processes all data items as combinations of zeros and ones because it is simple and economical for engineers to build electronic devices that can assume two stable statesone representing o and the other representing 1. It is remarkable that the impressive functions performed by computers involve only the most fundamental manipulations of os and is. The smallest data item in a computer can assume the value o or the value i. Such a data item is called a bit short for binary digit a digit that can assume one of two values . Computer circuitry performs various simple bit manipulations such as examining the value of a bit setting the value of a bit and reversing the value of a bit from i to o or from o to i . It is cumbersome for programmers to work with data in the low-level form of bits. Instead programmers prefer to work with data in such forms as decimal digits 09 letters AZ and az and special symbols . @ and I . Digits letters and special symbols are known as characters. The computer s character set is the set of all the characters used to write programs and represent data items. Computers process only is and os so a computer s character set represents every character as a pattern of is and os. Characters in Java are Unicode characters composed of two bytes each composed of eight bits. Java contains a data type byte that can be used to represent byte data. The Unicode character set contains characters for many of the world s languages. See Appendix F for more information on this character set. See Appendix B ASCII Character Set for more information on the ASCII American Standard Code for Information Interchange character set a subset of the Unicode character set that represents uppercase and lowercase letters digits and various common special characters. Just as characters are composed of bits fields are composed of characters or bytes. A field is a group of characters or bytes that conveys