ASCII: ex­pla­na­tion and examples

ASCII is a standard for the rep­re­sen­ta­tion of char­ac­ters by elec­tron­ic devices. To get a better un­der­stand­ing of what this means it helps to be aware of how a computer works in the first place. In a computer, computing processes are always based on the binary system. That means: ones and zeros determine the processes of a computer. ASCII too is based on this system. The original ASCII standard defines different char­ac­ters within seven bits – that is, seven digits showing either a 0 or a 1.

The eighth bit, which is one full byte, is tra­di­tion­al­ly used for checking purposes. The ASCII-based extended versions use this exact bit to extend the available char­ac­ters to 256 (2⁸).

Each character cor­re­sponds to a seven-digit sequence of zeroes and ones, which can then be rep­re­sent­ed as a decimal number, or as a hexa­dez­i­mal number. The ASCII char­ac­ters can be divided into several groups.

• Control Char­ac­ters (0–31 & 127): Control char­ac­ters are not printable char­ac­ters. They are used to send commands to the PC or the printer and are based on telex tech­nol­o­gy. With these char­ac­ters, you can set line breaks or tabs. Today, they are mostly out of use.
• Special Char­ac­ters (32–47 / 58–64 / 91–96 / 123–126): Special char­ac­ters include all printable char­ac­ters that are neither letters nor numbers. These include punc­tu­a­tion or technical, math­e­mat­i­cal char­ac­ters. ASCII also includes the space (a non-visible but printable character), and therefore, does not belong to the control char­ac­ters category, as one might suspect.
• Numbers (30–39): These numbers include the ten Arabic numerals from 0-9.
• Letters (65–90 / 97–122): Letters are divided into two blocks, with the first group con­tain­ing the uppercase letters and the second group con­tain­ing the lowercase.

In ASCII, the system converts binary numbers into printable and non-printable char­ac­ters according to a specified standard.

If you take a look at the ASCII table, you’ll find the char­ac­ters rep­re­sent­ed for various numeric values.

Example:

The binary number 01000001 can be written decimally as 65, hexa­dec­i­mal­ly as 41. The character encoded with this number is an “A”. If you now count down further, you will find the uppercase letters listed in al­pha­bet­i­cal order. So, the word “ASCII” would cor­re­spond to the following numerical values:

ASCII is still widely used today, even though UTF-8 has become more important when pre­sent­ing a text. However, Unicode has only been dis­plac­ing the old character encoding method used during the early days of the internet since 2008. The advantage of using UTF-8 is that the code is almost back­ward­ly com­pat­i­ble: ASCII is a subset of UTF-8, so the first 128 char­ac­ters are identical. Since ASCII can be con­sid­ered the lowest common de­nom­i­na­tor of most new encoding forms, the old encoding method is still used in emails and URLs.

In addition, ASCII has long been used for artistic purposes as well as technical ones: ASCII art uses ex­clu­sive­ly printable ASCII code char­ac­ters to produce creative works. The spectrum ranges from lettering to simple stick figures, to real paintings. ASCII artists use the different bright­ness levels of in­di­vid­ual char­ac­ters to create light and shade in their artworks.

The American Standards As­so­ci­a­tion (ASA, now known as ANSI for “American National Standards Institute”) approved the American Standard Code for In­for­ma­tion In­ter­change (ASCII) back in 1963. This set out binding spec­i­fi­ca­tion for how elec­tron­ic devices should represent char­ac­ters. Since the standard is US-American, it is often referred to as US ASCII.

Its pre­de­ces­sors include Morse code and the codes used in telexes, where a stan­dard­ized code (e.g. a fixed sequence of acoustic signals) is trans­lat­ed into text. Since computers cannot handle our alphabet, because their internal processes are based on the binary system, ASCII was in­tro­duced.

To this day, the standard has rarely been changed to adapt to new re­quire­ments. For example, extended versions exist that use an eighth bit so that national pe­cu­liar­i­ties such as the German umlauts (ä, ö and ü) can be rep­re­sent­ed. Latin-1 (ISO 88591-1), which is still popular in Germany, is based on the ASCII code.

However, it is still not possible to switch between the Latin alphabet and, for example, Arabic char­ac­ters. To this end character sets based largely on Unicode, such as UTF-8, are now well-es­tab­lished. Unicode provides space for more than a million different char­ac­ters. UTF-8 is also com­pat­i­ble with ASCII, encoding the first 128 char­ac­ters in the same way.