How to validate ASCII Text – PHP. Many modern character encoding schemes extend the character set used by ASCII by providing additional characters so as to not only maintain backward compatibility but also achieve the benefits of encoding more international characters. For example, 74 is 'J', 106 is 'j', 123 is , and 32 is a space. To convert to ASCII from textual characters, you should use the chr function, which takes an ASCII value as its only parameter and returns the text equivalent if there is one.
![]()
Contents.Overview ASCII was developed from. Its first commercial use was as a seven- code promoted by Bell data services.
Work on the ASCII standard began on October 6, 1960, with the first meeting of the 's (ASA) (now the or ANSI) X3.2 subcommittee. The first edition of the standard was published in 1963, underwent a major revision during 1967, and experienced its most recent update during 1986. Compared to earlier telegraph codes, the proposed Bell code and ASCII were both ordered for more convenient sorting (i.e., alphabetization) of lists, and added features for devices other than teleprinters.Originally based on the, ASCII encodes 128 specified into seven-bit integers as shown by the ASCII chart above. Ninety-five of the encoded characters are printable: these include the digits 0 to 9, lowercase letters a to z, uppercase letters A to Z,. In addition, the original ASCII specification included 33 non-printing which originated with; most of these are now obsolete, although a few are still commonly used, such as the, and codes.For example, lowercase would be represented in the ASCII encoding by 1101001 = 69 ( i is the ninth letter) = 105.History. Main article:ASCII reserves the first 32 codes (numbers 0–31 decimal) for: codes originally intended not to represent printable information, but rather to control devices (such as ) that make use of ASCII, or to provide about data streams such as those stored on magnetic tape.For example, character 10 represents the 'line feed' function (which causes a printer to advance its paper), and character 8 represents 'backspace'. Refers to control characters that do not include carriage return, line feed or as non-whitespace control characters.
Except for the control characters that prescribe elementary line-oriented formatting, ASCII does not define any mechanism for describing the structure or appearance of text within a document. Other schemes, such as, address page and document layout and formatting.The original ASCII standard used only short descriptive phrases for each control character. The ambiguity this caused was sometimes intentional, for example where a character would be used slightly differently on a terminal link than on a, and sometimes accidental, for example with the meaning of 'delete'.Probably the most influential single device on the interpretation of these characters was the ASR, which was a printing terminal with an available reader/punch option. Paper tape was a very popular medium for long-term program storage until the 1980s, less costly and in some ways less fragile than magnetic tape. In particular, the Teletype Model 33 machine assignments for codes 17 (Control-Q, DC1, also known as XON), 19 (Control-S, DC3, also known as XOFF), and 127 became de facto standards. The Model 33 was also notable for taking the description of Control-G (code 7, BEL, meaning audibly alert the operator) literally, as the unit contained an actual bell which it rang when it received a BEL character.
Because the keytop for the O key also showed a left-arrow symbol (from ASCII-1963, which had this character instead of ), a noncompliant use of code 15 (Control-O, Shift In) interpreted as 'delete previous character' was also adopted by many early timesharing systems but eventually became neglected.When a Teletype 33 ASR equipped with the automatic paper tape reader received a Control-S (XOFF, an abbreviation for transmit off), it caused the tape reader to stop; receiving Control-Q (XON, 'transmit on') caused the tape reader to resume. This technique became adopted by several early computer operating systems as a 'handshaking' signal warning a sender to stop transmission because of impending overflow; it persists to this day in many systems as a manual output control technique. On some systems Control-S retains its meaning but Control-Q is replaced by a second Control-S to resume output.
The 33 ASR also could be configured to employ Control-R (DC2) and Control-T (DC4) to start and stop the tape punch; on some units equipped with this function, the corresponding control character lettering on the keycap above the letter was TAPE and TAPE respectively.The Teletype could not move the head backwards, so it did not put a key on the keyboard to send a BS (backspace). Instead there was a key marked RUB OUT that sent code 127 (DEL). The purpose of this key was to erase mistakes in a hand-typed paper tape: the operator had to push a button on the tape punch to back it up, then type the rubout, which punched all holes and replaced the mistake with a character that was intended to be ignored.
Teletypes were commonly used for the less-expensive computers from, so these systems had to use the available key and thus the DEL code to erase the previous character. Because of this, DEC video terminals (by default) sent the DEL code for the key marked 'Backspace' while the key marked 'Delete' sent an escape sequence, while many other terminals sent BS for the Backspace key.
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, and, understand both). The assumption that no key sent a BS caused Control+H to be used for other purposes, such as the 'help' prefix command in.Many more of the control codes have been given meanings quite different from their original ones.
The 'escape' character (ESC, code 27), for example, was intended originally to allow sending other control characters as literals instead of invoking their meaning. This is the same meaning of 'escape' encountered in URL encodings, strings, and other systems where certain characters have a reserved meaning. Over time this meaning has been co-opted and has eventually been changed. In modern use, an ESC sent to the terminal usually indicates the start of a command sequence usually in the form of a so-called ' (or, more properly, a ') from ECMA-48 (1972) and its successors, beginning with ESC followed by a ' (left-bracket) character. An ESC sent from the terminal is most often used as an character used to terminate an operation, as in the. In (GUI) and systems, ESC generally causes an application to abort its current operation or to (terminate) altogether.The inherent ambiguity of many control characters, combined with their historical usage, created problems when transferring 'plain text' files between systems.
The best example of this is the problem on various. Teletype machines required that a line of text be terminated with both 'Carriage Return' (which moves the printhead to the beginning of the line) and 'Line Feed' (which advances the paper one line without moving the printhead). The name 'Carriage Return' comes from the fact that on a manual the carriage holding the paper moved while the position where the typebars struck the ribbon remained stationary.
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.operating systems (, etc.) used both characters to mark the end of a line so that the console device (originally ) would work. By the time so-called 'glass TTYs' (later called CRTs or terminals) came along, the convention was so well established that backward compatibility necessitated continuing the convention. When created he was inspired by some command line interface conventions used in 's. Until the introduction of in 1981, had no hand in this because their 1970s operating systems used EBCDIC instead of ASCII and they were oriented toward punch-card input and line printer output on which the concept of carriage return was meaningless. IBM's (also marketed as by Microsoft) inherited the convention by virtue of being loosely based on CP/M, and inherited it from MS-DOS.Unfortunately, requiring two characters to mark the end of a line introduces unnecessary complexity and questions as to how to interpret each character when encountered alone.
To simplify matters data streams, including files, on used line feed (LF) alone as a line terminator. And systems, and systems, adopted this convention from Multics. The original, and, on the other hand, used carriage return (CR) alone as a line terminator; however, since Apple replaced these operating systems with the Unix-based operating system, they now use line feed (LF) as well. The Radio Shack also used a lone CR to terminate lines.Computers attached to the included machines running operating systems such as TOPS-10 and using CR-LF line endings, machines running operating systems such as Multics using LF line endings, and machines running operating systems such as that represented lines as a character count followed by the characters of the line and that used rather than ASCII.
The protocol defined an ASCII ' (NVT), so that connections between hosts with different line-ending conventions and character sets could be supported by transmitting a standard text format over the network. Telnet used ASCII along with CR-LF line endings, and software using other conventions would translate between the local conventions and the NVT. The adopted the Telnet protocol, including use of the Network Virtual Terminal, for use when transmitting commands and transferring data in the default ASCII mode. This adds complexity to implementations of those protocols, and to other network protocols, such as those used for E-mail and the World Wide Web, on systems not using the NVT's CR-LF line-ending convention.The PDP-6 monitor, and its PDP-10 successor TOPS-10, used Control-Z (SUB) as an end-of-file indication for input from a terminal. Some operating systems such as CP/M tracked file length only in units of disk blocks and used Control-Z to mark the end of the actual text in the file. For these reasons, EOF, or, was used colloquially and conventionally as a for Control-Z instead of SUBstitute.
The end-of-text code , also known as, was 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. See also:Eventually, as 8-, and (and later ) computers began to replace, and computers as the norm, it became common to use an 8-bit byte to store each character in memory, providing an opportunity for extended, 8-bit relatives of ASCII. In most cases these developed as true extensions of ASCII, leaving the original character-mapping intact, but adding additional character definitions after the first 128 (i.e., 7-bit) characters.Encodings include (India), (Vietnam). Although these encodings are sometimes referred to as ASCII, true ASCII is defined strictly only by the ANSI standard.Most early home computer systems developed their own 8-bit character sets containing line-drawing and game glyphs, and often filled in some or all of the control characters from 0 to 31 with more graphics.
Computers used the 'upper' 128 characters for the Greek alphabet.The code used for their systems is probably unique among post-1970 codes in being based on ASCII-1963, instead of the more common ASCII-1967, such as found on the computer. 8-bit computers and computers also used ASCII variants.The IBM PC defined, which replaced the control characters with graphic symbols such as, and mapped additional graphic characters to the upper 128 positions. Operating systems such as supported these code pages, and manufacturers of supported them in hardware. Developed the (DEC-MCS) for use in the popular as one of the first extensions designed more for international languages than for block graphics. The Macintosh defined and Postscript also defined a set, both of these contained both international letters and typographic punctuation marks instead of graphics, more like modern character sets.The standard (derived from the DEC-MCS) finally provided a standard that most systems copied (at least as accurately as they copied ASCII, but with many substitutions). A popular further extension designed by Microsoft, (often mislabeled as ), added the typographic punctuation marks needed for traditional text printing.
ISO-8859-1, Windows-1252, and the original 7-bit ASCII were the most common character encodings until 2008 when became more common.introduced 32 additional control codes defined in the 80–9F range, as part of extending the 7-bit ASCII encoding to become an 8-bit system. See also:and the ISO/IEC 10646 (UCS) have a much wider array of characters and their various encoding forms have begun to supplant ISO/IEC 8859 and ASCII rapidly in many environments. While ASCII is limited to 128 characters, Unicode and the UCS support more characters by separating the concepts of unique identification (using called code points) and encoding (to 8-, 16- or 32-bit binary formats, called, and ).ASCII was incorporated into the Unicode (1991) character set as the first 128 symbols, so the 7-bit ASCII characters have the same numeric codes in both sets. This allows to be with 7-bit ASCII, as a UTF-8 file containing only ASCII characters is identical to an ASCII file containing the same sequence of characters. Even more importantly, is ensured as software that recognizes only 7-bit ASCII characters as special and does not alter bytes with the highest bit set (as is often done to support 8-bit ASCII extensions such as ISO-8859-1) will preserve UTF-8 data unchanged.
See also., an asteroid named after the character encoding. (ASCII as a subset of Unicode)., a glossary of computer programmer slang which includes a list of common slang names for ASCII characters.Notes.
Whether you’re new to Mac or have been using it for years, highly specialized things like shortcuts, special Mac symbols, and accented characters might result in a web investigation spiralling out of control.If you’ve just recently switched from Windows, you should know that Macs don’t really use alt codes to type special symbols. Instead, all of the most popular Unicode characters can be typed in right from the keyboard. Unfortunately, Apple could do a much better job of shining light at this functionality.For example, if you want to get a copyright symbol on Windows (©), you need to type in Alt 0169 — whereas, a copyright symbol on Mac is just Option + G. Similarly, a degree symbol on Mac (º) is Option + Zero and a registered trademark symbol on Mac (™) is Option + 2.Truth is there are many more like this and below we’ll explore different ways of how to type copyright symbol on Mac or any special characters Macs allow, where to find Apple keyboard symbols, and whether there’s an emoji keyboard on Mac. Even if you’ve been using your Mac for a while, it’s useful to look at all the possible keyboard combinations from time to time to refresh your memory and discover new ways of quickly inputting information.Luckily, it’s easy to show all Mac key symbols at once:. Go to System Preferences ➙ Keyboard. Check the box next to “Show keyboard and emoji viewers in menu bar”Now you can click on the language flag in your menu bar and choose Show Keyboard Viewer.
The interactive display will appear, showing all the keyboard symbols and altering the view in real time when you use modifier keys.Of course, even using all the modifier keys and combinations available, it’s impossible to fit all the characters in such constrained amount of space. To see all Mac key symbols, you need to select Show Emoji & Symbols option from the same language flag menu, or use a shortcut Control + Cmd + Space.Here, you’ll see all kinds of categories on the left: Emoji, Arrows, Currency Symbols, etc. In the center are all the characters within a given category. And on the right you can pick a font variation of the same symbol.To type in a TM symbol Macs use, for example:. Open your word processor of choice. Call the Mac symbols menu. Navigate to Letterlike Symbols on the sidebar.
![]() ![]()
Double-click on ™ to paste it into your editor. With the Show Emoji & Symbols window, you have access to nearly all Unicode characters you’ll ever need. However, if you need to use some special characters — such as a copyright symbol on Mac — rather frequently, it would be quite inconvenient to call up a menu and search for what you need every time. Of course, you can add the copyright symbol to your favorite characters, which will save you some time, but there’s a much better way.Macs allow you to create shortcuts for all keyboard symbols to be able to easily type them in whenever you need. For example, to create a shortcut for the copyright symbol on Mac:. Type in the © character into your editor as described above and copy it with Command + C. Open System Preferences ➙ Keyboard.
Navigate to the Text tab. Click the plus sign. Paste your © symbol in the With column on the right. Type in a desired key combination to trigger the copyright symbol on Mac in the Replace column on the leftAlthough this default shortcuts method works well for characters or emoji, it doesn’t effectively translate into longer strings of text or paragraphs. If you want to, for instance, create a shortcut that outputs a sales email template, you’d need to use a little nifty tool called Rocket Typist.is a full-featured text expansion app created to minimize repetition in composing any form of text-based communication. It’s essentially a small database of text snippets you’ll use over and over again.Starting with Rocket Typist is easy: use File ➙ New to create a new snippet, specify the abbreviation, fill out as much text (sentences or even paragraphs) as you need, and then use the abbreviation to expand text in any application.
Sometimes, the Mac keyboard symbols you need are only available in another language — say, they could be Cyrillic-based. To access them, you’d need to enable another keyboard layout on your Mac.Luckily, it’s easy to do:. Go to System Preferences ➙ Keyboard. Navigate to Input Sources. Click the plus sign. Choose the language you need and press AddNow, the second keyboard layout will be activated. Don’t forget to check the box next to “Show Input menu in menu bar” to see which layout is currently active.
The standard shortcut to switch between layouts is Cmd + Space, but you can also change it to Caps Lock key in the Input Sources options. Extra tip: typing emoji on iPhone is much easier if you add an emoji keyboard layout to your languages.
In some cases, you might just want to access a variation of the symbol that’s already on your keyboard, such as an accented letter.One way to do this is to find the character of your choice in the Keyboard Viewer, as described above. Another way is to use a keyboard shortcut. You can get an acute accent by typing Option + E and then the letter. Similarly, circumflex is Option + I, grave accent is Option + backquote, tilde is Option + N, and umlaut is Option + U.A quicker option though is to simply press the key of the letter you want to modify and hold it for a second until a small menu appears. Then just choose a number that corresponds to the modification you seek. If your studies or line of work require the use of complex math, you might be spending too much time crafting LaTeX and MathML expressions by hand.
But as with nearly everything else nowadays, there’s an easier way.is a Mac app specifically developed to write complex equations in academic papers and math documents. Instead of composing dozens of obscure symbols together, the app allows you to hand-write the equation using your trackpad (or mouse) and output perfect LaTeX or MathML, ready for publication.Search for anything instantlyIt’s likely that you won’t retain all the information provided here. But don’t worry, the only thing you need to keep is a supercharged search that can take you right back to the answer you’re looking for.is an intelligent search for your Mac that contextually analyzes the query and outputs a range of possible solutions, whether it’s launching a certain app, looking it up online, or performing a pre-defined action.Any question about Mac keyboard shortcuts symbols — such as “how to type copyright symbol on Mac?” — would be met with a guiding response. And all you have to do to start Lacona is press Option + Space.So there are a lot of things your Mac is capable of that you might have not even considered before. With regards to symbols and characters, what you see on the keyboard is just a tiny slice compared to the total amount available. Using Mac symbols properly will enrich your communication, making it clear and efficient, especially if you get used to creating snippets with Rocket Typist, transferring math equations with MathKey, and keeping everything at the tips of your fingers with Lacona.Best of all, the apps mentioned above are available to you on a free trial through, a platform of more than 150 specific Mac apps that are designed to make your days more productive and fun.
Now you’re ready to solve some equations!
![]() Comments are closed.
|
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
January 2023
Categories |