Code

About Code

We use different types of code in the number system. For input processing, we need to codeAnd after completing the process we need to decode. In the computer system for representing many types of signs, the number of special characters individually binary bits is used. The binary bits are converted in different ways for representing the individual signals. 


In this process, the code converted into signs, numbers, and special characters.

We have to use different types of codes in different situations. Here are some types of code 

  1. BCD code
  2. Alphanumeric code
  3. ASCII code
  4. Unicode
  5. Octal Code
  6. Hexadecimal code
  7. EBCDIC code


BCD code


BCD code is a famous code. Its full form is Binary Coded Decimal. For representing the decimal number in binary number this code is used. 

We know all the decimal numbers are built by  0,1,2,3,4,5,6,7,8,9.

For representing these 10 numbers we need 4-bit binary numbers. By 4 bit 2⁴ that means 16 different situations can be represented.

So, by using 16 situations different types of BCD codes can be created. 

Different types of BCD code: BCD 8421 code, BCD 7421 code, BCD 5421 code.

Be noted that BCD is not a number system.

The representation process of decimal numbers in BCD code is easier than representing the binary number system.


Alphanumeric code


In the computer there are different types of letters, numbers, mathematical signs and also many special characters are used. For representing these a special type of code is used. That is called Alphanumeric code. Not only in computers but also in different technological procedures there is a badly need for this code. For many needs it has build. 

Examples: 

ASCII-7 :

It is an alphanumeric code. By using this code 2⁷ = 128 number of signs can be defined.

ASCII-8 :

It is also an Alphanumeric code. 2⁸ = 256 number of signs can be defined by using this.



ASCII code


American Standard Code for Information Interchange is the full form of ASCII. It is a regularly used code. It is a 7-bit code. 

By using this code 2⁷ = 128 number of numbers, letters, different signs, and also many special characters can be represented.

ASCII-7 code :

For A  :

  
1
0
0
0
0
0
1
  
In ASCII code 

Left 3 are Zones

Right 3 are numerical bits

But at the left side adding a parity bit, ASCII is converted into an 8-bit code.

In the present system, the ASCII -8 code is known or called an ASCII code.
As an example 

ASCII-8 code :

For A  : 

0
1
0
0
0
0
0
1

  ↑

Parity bit (Most left)

Use of ASCII code:

- In microcomputers
- In computer input, output devices(Keyboard, Monitor, Printer)
 for alphanumeric data transmission.




EBCDIC code



Its full form is Extended Binary Coded Decimal Information Code. It is an 8-bit code. It is also called the Extended EBCDIC code. By using this code 2⁸ = 256 numbers, letters and special signs can be represented.


At the primary level this code used in 360 and 370 series computers.

In this code used zone bits are given below.

Condition
Used Zone bit
0 to 9
1111
A to Z
1100,1101,1110
Special Sign
0100,0101,0110,0111

Decimal numbers are represented 8421 code then we add 1111 zone bit with each number for representing EBCDIC code.

Unicode



The full form of Unicode is the Universal code. For adding all the language of the universe in computers larger companies have created this. Unicode is a 16-bit code. Unicode is used for representing different types of text and characters.

By Unicode 2¹⁶ = 65536 individual sign can be defined. That's why in those countries where language representation by 8 bit is not possible there Unicode is used. 

Unicode supports like Windows 200, OS/2 operating systems.  

Differences 

BCD code and alphanumeric code



BCD code


Alphanumeric code


We use BCD code for representing each digit of the decimal number in the 4-bit binary number


This code is used for representing different letters, mathematical signs, and also some special characters.

In this code by 4 bit, 2⁴ or 16 different conditions are represented.


By 7 bit of ASCII-7, code 2⁷ or 128 different conditions are represented.

It is a 4-bit code


It is a code of 8 bit or 7 bit.

Example: BCD 8421


Example: ASCII-7, ASCII-8



BCD code and ASCII code



BCD code


ASCII code


Full meaning: Binary coded decimal.


Full meaning: American Slandered Code for Information Interchange.

In this code by 4 bit, 2⁴ or 16 different conditions are represented.


By this code, 2⁷ or 128 different conditions are represented.

It is a 4-bit code.


It is a code of 7 bit.

For converting decimal number into a binary number.

Used in the microcomputers.





BCD code and binary number



BCD code


Binary number


We use BCD code for representing each digit of the decimal number in a 4-bit binary number


We get binary numbers by dividing the decimal numbers by 2.

It is easier to convert a decimal number into BCD code


Converting a decimal number into a binary number is not too easier.

BCD is not a number system. It is a code.


It is a Number system.

More memory use than binary number system.


Less memory use than BCD code.