The table shows that the character with code value 0 is a control character, 'called the NULL character. The end-of-text code ETXalso known as Control-Cwas inappropriate for a variety of reasons, while using Z as the control code to end a file is analogous to it ending the alphabet and serves as a very convenient mnemonic aid.
The "escape" character ESC, code 27for example, was intended originally to allow sending other control characters as literals instead of invoking their meaning.
Unix and Unix-like systems, and Amiga systems, adopted this convention from Multics. The character column shows the key s that must be pressed. Notice that the character 'A' has the code value of 65, 'B' has the value 66, and so on.
The name "Carriage Return" comes from the fact that on a manual typewriter the carriage holding the paper moved while the position where the typebars struck the ribbon remained stationary.
Note, after the escape backslash, a leading zero should not be included in writing octal or hexadecimal numbers.
The entire carriage had to be pushed returned to the right in order to position the left margin of the paper for the next line. The inherent ambiguity of many control characters, combined with their historical usage, created problems when transferring "plain text" files between systems.
Similarly, the digit symbol characters '0' through '9' are also in an increasing contiguous sequence starting at the code value The Unix terminal driver could only use one code to erase the previous character, this could be set to BS or DEL, but not both, resulting in a long period of annoyance where users had to correct it depending on what terminal they were using shells that allow line editing, such as kshbashand zshunderstand both.
The ASCII code associates an integer value for each symbol in the character set, such as letters, digits, punctuation marks, special characters, and control characters. Consequently, a character data type may optionally represent signed values; however, for now, we will assume that character data types are unsigned, i.
Over time this meaning has been co-opted and has eventually been changed.