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The NULL character (code 0) is represented by Ctrl-@, "@" being the code immediately before "A" in the ASCII character set. For convenience, some terminals accept Ctrl-Space as an alias for Ctrl-@. In either case, this produces one of the 32 ASCII control codes between 0 and 31.
Many Unicode characters are used to control the interpretation or display of text, but these characters themselves have no visual or spatial representation. For example, the null character (U+0000 NULL) is used in C-programming application environments to indicate the end of a string of characters.
In 1973, ECMA-35 and ISO 2022 [18] attempted to define a method so an 8-bit "extended ASCII" code could be converted to a corresponding 7-bit code, and vice versa. [19] In a 7-bit environment, the Shift Out would change the meaning of the 96 bytes 0x20 through 0x7F [a] [21] (i.e. all but the C0 control codes), to be the characters that an 8-bit environment would print if it used the same code ...
ASCII codes represent text in computers, telecommunications equipment, and other devices. ASCII has just 128 code points, of which only 95 are printable characters, which severely limit its scope. The set of available punctuation had significant impact on the syntax of computer languages and text markup.
In all modern character sets, the null character has a code point value of zero. In most encodings, this is translated to a single code unit with a zero value. For instance, in UTF-8 it is a single zero byte. However, in Modified UTF-8 the null character is encoded as two bytes: 0xC0,0x80. This allows the byte with the value of zero, which is ...
If the terminating character is a letter, the letter is the keycode value, and the optional number is the modifier value. The modifier value defaults to 1, and after subtracting 1 is a bitmap of modifier keys being pressed: Meta+Ctrl+Alt+⇧ Shift. So, for example, <esc>[4;2~ is ⇧ Shift+End, <esc>[20~ is function key F9, <esc>[5C is Ctrl+→.
The delete control character (also called DEL or rubout) is the last character in the ASCII repertoire, with the code 127. [1] It is supposed to do nothing and was designed to erase incorrect characters on paper tape. It is denoted as ^? in caret notation and is U+007F in Unicode.
Six-bit BCD code was the adaptation of the punched card code to binary code. IBM applied the terms binary-coded decimal and BCD to the variations of BCD alphamerics used in most early IBM computers, including the IBM 1620 , IBM 1400 series , and non- decimal architecture members of the IBM 700/7000 series .