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.