Sunday 23 August 2015

BINARY CODING SCHEMES

          Now let us consider an important question. How are characters represented 0's and 1's ("off" and "on" electrical states) in the computer? The answer is in the use of binary coding schemes. A binary coding scheme assigns a unique sequence of bits to each character. (See the below image). Two of the most popular binary coding schemes use eight bits or one byte. These two codes are ASCII and EBCDIC. A recently developed code, unicode, uses 16-bits.


                 
  • ASCII, pronounced "as-key" stands for American Standard Code for Information Interchange. This is an older code which is still widely used for microcomputers. For example, the number 3 is represented in ASCII code as 0011 0011.
  • EBCDIC, pronounced "eb-see-dick", stands for Extended Binary Coded Decimal Interchange Code. It is an older code originally developed by IBM and is used primarily for large computers. For example, the number 3 is represented in EBCDIC code as 1111 0011.
  • Unicode is a family of 16-bit codes that support both ASCII and EBCDIC. It is also used for international languages like Chinese and Japanese. These languages have too many characters to be represented by the 8-bit ASCII and EBCDIC codes.
          When you press a key on the keyboard, a character is automatically converted into a series of electronic pulses that the system can recognize. For example, pressing the number 3 on a keyboard  causes an electronic signal to be sent to the microcomputer's  system unit where it is converted to the character code of 0011 0011.
          Coding schemes are particularly important to hardware designers and computer programmers for tracking down errors and other types of problems. But why are coding schemes important to end users? There are several reasons. One of the most important is that data created by one computer system using one coding scheme cannot be directly accessed and used by another computer system using a different coding scheme. Generally, this is not a problem if both computers are microcomputers since both would most likely use Unicode. And most microcomputer applications store data using this code. However, problems can occur when data is shared between microcomputers and older computer that use EBCDIC code. The data may have to be translated from one coding scheme to the other before processing can begin. Fortunately, special conversion problems are available to help with this translation.

    ASCII and EBCDIC binary coding schemes.

No comments:

Post a Comment