Binary Data Types

Representing text using binary. 

A common method to represent text data is called ASCII (pronounced “as-kee”) and was published in 1963. The letters stand for American Standard Code for Information Interchange.

ASCII uses 7 bits, allowing 128 different possible codes, with the eighth one sometimes used as a check bit to see if the message was received correctly.

This decision was based on early teleprinters, where paper tape could fit only eight holes across. Holes represented a one. Eight bits can represent 28 = 256 different symbols. Everyone at the time thought that this would be more than enough, as in English there are only 26 letters of the alphabet, upper and lower cases, numerals 0-9, punctuation and some other special symbols. 

When we type words in at the keyboard, the signals travel from the keys to the CPU. At this stage of the journey the binary codes are called keyboard scan codes. The computer, however, receives these scan codes and translates them into ASCII to represent the character. 

Here is a small snippet of binary ASCII code:

This is difficult to read, which is why ASCII tables are often written in decimal form. The binary above in decimal looks like this: 

66 73 78 65 82 89

See if you can translate this code into a word using the ASCII table in Table 2.4 

Task 8: Building an ASCII translator

In this activity you will use a spreadsheet to create a translator for binary ASCII code. We have formed the beginning of a well-known joke about binary. Your task is to discover the rest of the joke and explain it!

You will need to use Fill down and Look up tables.

What about other languages? 

By using bits ASCII can represent 256 different symbols. But computers are not only expected to handle the 26 upper case and 26 lower case Roman or Latin characters used in English.

There are many alphabets in use throughout the world. 

What about the Russian or Arabic alphabets and how do we represent the many Chinese characters?

To solve this problem another system called Unicode was invented. To make it easy to switch, ASCII was included as part of Unicode. Thus, the decimal value of 84 represents uppercase “T” in both systems.

Unicode allows as many as 1 1 1 4 1 1 2 possible characters. At present, only about 10% of these have been used.