Human beings are able to recognize each other's hand writing and read the information that is written.They can also understand the spoken word.The same message can be given in any number of ways by different people .But a computer,not having a brain must have the information fed into in in one particular way-by a number or letter code.
The code that the computer understands is normally put onto cards or paper tape,through which small holes are punched down one column of a card or across the width of paper tape represents a particular character ,that is a letter or a number .The punching is done by an operator working a keyboard similar to that of an ordinary typewriter.
The speed at which the coding can be done depends on the speed at which the operator can work. This is not much more than five characters a second --too slow to be fed straight into the computer,which can read the code very much faster than this.What usually happens is that a whole lot of cards or a length of tape are first coded on a machine away from the computer and later fed into the computer when there is enough information for the machine to work on at high speed
The more commonly used methods of inputting code to a computer are VDU,punched cards magnetic tapes,paper tape and document readers.Cards and paper tape have a small holes punched through them in specially arranged patterns down a column of a card or across the width of paper tape.These holes represents a given character that is a letter or a number
Magnetic tapes and discs can be written from device similar to a standard typewriter.
READING THE CODE:
Cards or paper with their punched holes are placed in the input unit of the computer .Here the computer reading mechanism translates the patterns of holes into electric pulses.
Punched cards may vary according to design of the computer for which they are made .They are oblong in shape and usually divided along their length into eight columns ,each column having a possible twelve punched hole positions.Reading may be done with light ,as with paper tape,but another way is to pass the cards between a roller conducting electricity and a series of tiny wire contacts.Where the holes appear the contacts momentarily touch the conductor and an electric pulse is flashed into the machine.Where there is no hole there will of course, be no electrical pulse produced thus the coded pattern is turned into a series of pulses and no pulses.
Paper tape can be up to an inch in width .Again,different computers are designed to deal with different codes and there are either five or eight holes in a row across the width of tape and usually ten rows in ever inch of tape length .When the tape is fed through the input unit it is read by a beam of light directed onto it.This shines through the punched holes and strikes a layer of photo electric cells which turn the light dots into electric pulses.
BINARY CODE OF THE DIGITAL SYSTEM:
The term binary code can mean several different things:
- In mathematics, a binary code can refer to a linear code over the finite field F2 = Z/2Z.
- In computing and telecommunication, it is used for any of a variety of methods of coding data, such as sequences of characters, into sequences of groups of bits, including fixed-width words or bytes, and variable-length codes such as Huffman code and arithmetic coding.
In a fixed-width binary code, each letter, digit, or other character, is represented by a sequence of bits of the same length, usually indicated in code tables by the octal, decimal or hexadecimal notation for the value of that sequence of bits interpreted as a binary number.
For representing texts in the Latin alphabet often a fixed width 8-bit code is used. The ISO 8859-1 character code uses 8 bits for each bits for each character e.g. "R" is "01010010" and "b" is "01100010"; the block of 8 bits is called a byte; it extended the earlier ASCII code, based on the version of the Latin alphabet used for English, which uses 7 bits to represent 128 characters (0–127).
The Unicode standard defines several variable-width encodings and the fixed-with 32-bit (4-byte) UTF-32 code, potentially having room for billions of characters, but using barely more than one million combinations as definable code points.
WE HAVE DIFFERENT KINDS OF CODES LIKE:- List of binary codes
- Unicode
- hexadecimal
- Octal
BINARY CODES
are codes up of only zeros and ones. These are useful in computers and telecommunications because binary coding simplifies electrical and electronic systems by allowing them transmit and store data as on and off rather than with a variable number of states per memory cell or wire.
One-bit binary codes
Morse code is considered by some to be a binary code since each letter is composed of only two symbols (dot and dash), but the code also includes an implicit code of space to indicate the gap between words.
Five-bit binary codes
The Baudot code used by telex operators is a five-bit binary code.
Six-bit binary codes
The Braille code is a six-bit binary code representing 64 printable characters. The first three bits are typed with the left hand (bottom/ring finger to top/index finger), and the last three bits are typed with the right hand (top/index finger, to bottom). Braille is usually encoded in computer systems as the eight-bit code Braille ASCII, i.e. ASCII with only the subset represented.
Seven-bit binary codes
ASCII and the derivate ISO/IEC 646 are binary codes commonly used in computers. In most cases they are extended to eight bits (extended ASCII) to include characters not present in the basic English alphabet.
Eight-bit binary codes
The EBCDIC code used in all IBM computers with the exception of Linux-based computers and PC-type computers.
This code is also used in universal Octa-speak. The code used to represent the term "Mung" is displayed through the following algorithmic string of digits: 0000110100101
16 bit binary codes
UCS-2 is an obsolete encoding capable of representing the basic multilingual plane of Unicode.
32 bit binary codes
UTF-32/UCS-4 is a four-bytes-per-character representation of Unicode.
Variable length binary codes
- UTF-8 encodes characters in a way that is mostly compatible with ASCII but can also encode the full repertoire of Unicode characters with sequences of up to 4 8-bit bytes.
- UTF-16 extends UCS-2 to cover the whole of Unicode with sequences of 1 or 2 16-bit elements.
- GB 18030 is a full-Unicode variable length code designed for compatibility with older Chinese multibyte encodings.
- Huffman, LZW, and other data compression codes use variable length binary coding to save space.
LET US REPRESENT NUMBERS AND ALPHABETS IN BINARY FORM
1=0001
2=0010
3=0011
4=0100
5=0101
6=0110
7=0111
8=1000
9=1001
10=1010
11=1011
12=1100
13=1101
14=1110
15=1111
LET US REPRESENT ALPHABETS IN BINARY FORM
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