Computer codes definition | types of computer codes
In this article i will tell you about computer codes definition and their types, but first of all you need to know what is computer code then we will go on computer codes definition.
Character coding schemes (also known as pc codes) are standards for representing characters in computers. They allow effortless transfer/exchange of statistics between computers, and between pc and peripheral units connected to computers. They additionally allow independent development of numerous hardware and software elements for a large range of computers. Although many coding schemes have developed over the years, we will discuss beneath only the most in many instances used pc codes.
Types of computer codes
- BCD code
- EBCDIC code
- ASCII code
Computer codes definition
Computer codes definition of BCD code
Binary coded decimal (BCD) is one of the early computer codes. In BCD code, each digit of a decimal quantity is represented by its binary equal alternatively of changing the entire decimal cost to a binary number. This makes the conversion procedure easier.
Definition of EBCDIC code
The predominant hassle with BCD code is that it can signify solely 64 different characters. This is not sufficient for offering decimal numbers (10),lowercase (small) letters (26) , uppercase (capital) letters (26), and a large range of other one-of-a-kind characters (28+).
Hence , researches extended BCD code from a 6-bit code to an 8-bit code. The brought two bits are used as extra zone bits, expanding the quarter to 4 bits. The resulting code is referred to as the Extended Binary-Coded Decimal Interchange Code (EBCDIC).
In the code, it is feasible to characterize 256 distinctive characters, as an alternative of sixty four In addition to the a number personality requirements , this additionally allows a large variety of printable characters and numerous non-printable manage characters. System clothier allow use of manage characters to manipulate such activities as printer vertical spacing, motion of cursor on terminal screen, etc.
Out of 256 possible combinations, numerous are still reachable for new characters assignments. Hence, the code can nevertheless grow, as new necessities develop.
Since EBCDIC is an 8-bit code, we can divide it without difficulty into 4-bits corporations and use one hexadecimal digit for representing every of these. Hence, computer authorities use hexadecimal quantity machine as shortcut notation for reminiscence dump in computers that use EBCDIC for interior illustration of characters. This result is a one-to-four reduction in volume of memory dump.
Definition of ASCII code
Another widely used computer code is the American Standard Code for Information Interchange (ASCII). Several American computer manufacturer have adopted ASCII as their computer’s internal code. This code is popular in data communications, is used almost exclusively to represent data internally in microcomputers, and frequently found in larger computers produced by some vendors.
American National Standards Institute (ANSI) published ASCII standard in 1963. However, the standard lacked lowercase letters and ANSI subsequently revised ASCII in 1967. Later revisions in 1968, 1977, and finally in 1986 brought it in its present form. Today, ASCII is one of the most popular and widely supported character encoding standards.
ASCII is of two types
ASCII-7 is a 7-bit code that can characterize 128 distinctive characters. Computers the usage of 8-bit byte (group of 8 bits for 1 byte) and the 7-bit ASCII both set the 8th bit (leftmost bit) of every byte as zero or use it as a parity bit.
ASCII-8 is an prolonged version of ASCII-7. It is an 8-bit code that can signify 256 distinctive characters. It adds the extra bit to the left of the seventh bit (leftmost bit) of ASCII-7 codes.
Need for Unicode?
As computers becomes a popular tool for doing all kinds of data processing across the world, their usage could not be limited to english language users only. Hence, people started developing computer systems that could allow interaction and processing of data in local languages of users (e.g., Hindi, Japanese, Chinese, Korean, etc).
This required support of local language characters and other language specific symbols on these computer systems. ASCII or EBCDIC did not have enough number of bits to accommodate all the characters and language-specifiv symbols of a local language, in addition to english alphabet character and special character.
The unicode standard was designed to overcome these problems. It is a universal character-encoding standard used for representation of text for computer processing. The offical unicode website (http://www.unicode.org) states that it is an encoding system that “provides a unique number for every character, no matter what the platform, no matter what the program, no matter what the language”.
Today, unicode is a universal accepted character-encoding standard because :
- It provides a consistent way of encoding multilingual plain text. This enable data transfer through different systems without the risk of corruption.
- It defines codes for character used in all major languages of the world used for written communication. This enables a single software product to target multiple platform, languages, and countries without re-engineering.
- It also defines codes for special characters (such as various types of punctuation marks), mathematical symbols, technical symbols, and diacritics. Diacritics are modifying character marks such as tilde (~), that are used in conjunction with base character to represent accented letters (indicating different sound -for example, ñ).
- It has the capacity to encode as many as a million characters. This is large enough for encoding all known characters including all historic scripts of the world as well as common notational system.
- It assign each character a unique numeric value and name keeping character coding simple and efficient.
- It reserves a part of the code space for private use to enable users to assign codes for their own characters and symbols.
- It affords simplicity and consistency of ASCII .
- It specifies and algorithm for presentation of text with bi-directional behaviour.
Unicode has a lot of room to accommodate new characters. Moreover, its growth process is strictly additive in the sense that new characters can be added easily but existing characters cannot be removed.
This feature ensures that interpretation of data once encoded in unicode standard will remain in the same way by all future implementations that conform to original or later version of the unicode standard.
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