## ASCII-Code

# ASCII-Code

All electronic communications involving computers are expressed in binary

language which involves only two symbols. These are 0 for off and 1 for on.

Since normal communications between humans over large distances is both in

letters and numbers it earlier became necessary to come up with a coding

method capable of handling both cases. The result was a coding system

developed in this country in the early 1960s now known as ASCII(American

Standard Code for Information Interchange). We want here to show how this

code works.

Our starting point is to write down the first few integers and underneath them give

their binary form. Also we add a third row giving the 26 letters of the alphabet

written in sequential order. We summarize this information in the following three

tables –

1 2 3 4 5 6 7 8 9 10

0 10 11 100 101 110 111 1000 1001 1010

A B C D E F G H I J

11 12 13 14 15 16 17 18 19 20

1011 1100 1101 1110 1111 10000 10001 10010 10011 10100

K L M N O P Q R S T

21 22 23 24 25 26

10101 10111 11000 110001 110010 110111

U V W X Y Z

Now the major idea behind ASCII is that we can assign a number for each letter

of the alphabet and then convert it to binary form. The difficulty, as seen from the

above tables, is that one can not yet distinguish between a binary expression

being a number or letter. Certainly, as things stand, 110001 could refer to either

the number 24 or the letter X. Likewise 1000 could be 8 or H. To remedy this

difficulty ASCII lengthens the number of bits for each element to eight and then

replaces the first three digits on the left by 010 to indicate a letter. Thus the letter

M in binary reads 01001101 and S in binary is 01010011. A number has the first

four symbols on the left replaced by 0011. That is, the number 2 is written as

00110010. Using eight elements to represent a letter or number allows extra

space for punctuation marks, small letters, and mathematical operation signs.

The basic idea behind the ASCII coding procedure is that each symbol has a

specific binary number attached to it. The original ASCII coding of 1963 involved

128 characters . Later extensions added several hundred more. If you convert

the binary 01010011 into decimal, one gets the ASCII number of 83. Thus S in

ASCII is 83 which converts to 01010011 in binary. There are available on the

internet numerous conversion tables.

In cryptography one would disguise this batch of elements by multiplying things

by a large random number before sending the encrypted message out to a

receiver( and anyone else who may be listening). Only persons familiar with the

random number being used will be able to decipher the massage by dividing the

encrypted massage by the random number being used. As we will show in an

upcoming article, even certain semi-random numbers may be used for an

effective encryption. For most cryptography applications it is sufficient to deal

only with the thirty six ASCII symbols representing the numbers 0 through 9 and

the capital letters A through Z. A table giving all 36 groups follows