IST SEMESTER BCA IGNOU STUDY NOTES-BLOCK1-UNIT2-FUNCTIONING OF A COMPUTER -PC AND HARDWARE- ASCII AND UNICODE -PC AND HARDWARE

ASCII = Old, limited (English only)

Unicode = Modern, global (all languages + emojis)

An alphanumeric code has to represent 10 decimal digits, 26 alphabets and certain other

symbols such as punctuation marks and special characters. Therefore, a minimum of six

bits is required to code alphanumeric characters (26

= 64, but 25

= 32 is insufficient).

With a few variations this 6 bit code is used to represent alphanumeric characters

internally. However, the need to represent more than 64 characters (to incorporate

lowercase and uppercase letters and special characters), have given rise to seven- and

eight- bit alphanumeric codes. ASCII code is one such seven bit code that is used to

identify key press on the keyboard. ASCII stands for American Standard Code for

Information Interchange. It's an alphanumeric code used for representing numbers,

alphabets, punctuation symbols and other control characters. It’s a seven bit code, but for

all practical purposes it’s an eight bit code, where eighth bit is added for parity

Unicode is a computing industry standard for the consistent encoding, representation and

handling of text expressed in most of the world's writing systems. Developed in

conjunction with the Universal Character Set standard and published in book form as The

Unicode Standard, the latest version of Unicode consists of a repertoire of more than

107,000 characters covering 90 scripts, a set of code charts for visual reference, an

encoding methodology and set of standard character encodings, an enumeration of

character properties such as upper and lower case, a set of reference data computer files,

and a number of related items, such as character properties, rules for normalization,

decomposition, collation, rendering, and bidirectional display order (for the correct

display of text containing both right-to-left scripts, such as Arabic and Hebrew, and leftto-right scripts. Unicode can be implemented by different character encodings. The most

commonly used encodings are UTF-8 (which uses one byte for any ASCII characters,

which have the same code values in both UTF-8 and ASCII encoding, and up to four

bytes for other characters), the now-obsolete UCS-2 (which uses two bytes for each

character but cannot encode every character in the current Unicode standard), and UTF16 (which extends UCS-2 to handle code points beyond the scope of UCS-2).

The Unicode Consortium, the nonprofit organization that coordinates Unicode's

development, has the ambitious goal of eventually replacing existing character encoding

schemes with Unicode and its standard Unicode Transformation Format (UTF) schemes,

as many of the existing schemes are limited in size and scope and are incompatible with

multilingual environments. Unicode's success at unifying character sets has led to its

widespread and predominant use in the internationalization and localization of computer

software. The standard has been implemented in many recent technologies, including

XML, the Java programming language, the Microsoft .NET Framework, and modern

operating systems.