Misplaced Pages

#637362

96-514: In 1981, the Education Departments of Western Australia and South Australia announced joint tenders calling for the supply of personal computers to their schools. Acorn's Australian computer distributor, Barson Computers, convinced Joint Managing Directors Hermann Hauser and Chris Curry to allow the soon to be released Acorn BBC Microcomputer to be offered with disk storage as part of the bundle. They agreed on condition that Barson adapted

192-525: A shift function (like in ITA2 ), which would allow more than 64 codes to be represented by a six-bit code . In a shifted code, some character codes determine choices between options for the following character codes. It allows compact encoding, but is less reliable for data transmission , as an error in transmitting the shift code typically makes a long part of the transmission unreadable. The standards committee decided against shifting, and so ASCII required at least

288-522: 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 manually-input 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 with the less-expensive computers from Digital Equipment Corporation (DEC); these systems had to use what keys were available, and thus

384-458: A character count followed by the characters of the line and which used EBCDIC rather than ASCII encoding. The Telnet protocol defined an ASCII "Network Virtual Terminal" (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

480-805: A cloud based Unified Communications solution nominated by Gartner Inc. as Cool Vendor in Unified Communications, 2017 . In 2022, he invested in the Munich based quantum computing startup planqc, a spin-off from the renowned Max Planck Institute for Quantum Optics, and joined the advisory board. Hauser was voted the UK's "Computer Personality of the Year" of 1984. In 2010, Eureka , in its "100 most important scientists", placed Hauser at 51. He became patron of The Centre for Computing History in December 2011, 30 years after

576-459: A colon then the drive number, a dot, then the directory letter, another dot, and the name. For example, a file in the default directory of "drive" 2 called BOB would have a complete specification of :2.$ .BOB . The drive and directory specifiers are both optional. "Directories" in the DFS are single character prefixes on filenames - such as F in F.BankLtr - used to group files. The arrangement

672-409: A file's data must be stored in a single run of consecutive sectors, but free space is prone to becoming fragmented . Random-access file writes fail when the end of the file reaches the beginning of the next, even though there may be free sectors elsewhere on the disc. In such cases the DFS aborts with a Can't extend error. SAVE is also unable to split a file to fit the available space, but as

768-477: A holding company to begin work on marketing the NetStation. NetChannel was sold to AOL in 1996. He claimed in the 1990s that the networking technology used for AppleTalk was based on the (unpatented) Cambridge Ring . In 1997 he co-founded Amadeus Capital Partners Ltd, a venture capital company, and in 1998 he co-founded Cambridge Network with David Cleevely and Alec Broers . In 2000, Plastic Logic

864-491: A line terminator. The tty driver would handle the LF to CRLF conversion on output so files can be directly printed to terminal, and NL (newline) is often used to refer to CRLF in UNIX documents. Unix and Unix-like systems, and Amiga systems, adopted this convention from Multics. On the other hand, the original Macintosh OS , Apple DOS , and ProDOS used carriage return (CR) alone as

960-600: A line terminator; however, since Apple later replaced these obsolete operating systems with their Unix-based macOS (formerly named OS X) operating system, they now use line feed (LF) as well. The Radio Shack TRS-80 also used a lone CR to terminate lines. Computers attached to the ARPANET included machines running operating systems such as TOPS-10 and TENEX using CR-LF line endings; machines running operating systems such as Multics using LF line endings; and machines running operating systems such as OS/360 that represented lines as

1056-540: A non-standard disc format. Beyond that, the Solidisk implementation introduced proprietary "chained" catalogues which allowed unlimited files per disc (only constrained by the disk size). Other features in third-party implementations included being able to review free space, and built-in FORMAT and VERIFY commands, which were shipped on a utility disc with the original Acorn DFS. Acorn followed up their original DFS series with

SECTION 10

#1733093088638

1152-518: A paperback book", featuring a screen and stylus for interaction and employing a "book" metaphor known as Hyperpage. The company planned to launch its first product after Christmas 1990, featuring an approximately A5-sized reflective display, automatic recognition of printed, as opposed to cursive, characters, and employing a multipurpose chip called Hercules featuring a static, low-power ARM core. A licensing agreement had been signed with Acorn for access to that company's hardware and software technology, and

1248-401: A real-time clock) but instead offer a peculiar feature: a modification count. Every time the catalogue is updated, the count increments. The count is shown in parentheses after the title in the first line of the disc catalogue, such as the 12 in the catalogue listing shown earlier. The DFS also supports a means to start up disc software based on a key sequence. If the shift key is held while

1344-591: A reserved device control (DC0), synchronous idle (SYNC), and acknowledge (ACK). These were positioned to maximize the Hamming distance between their bit patterns. ASCII-code order is also called ASCIIbetical order. Collation of data is sometimes done in this order rather than "standard" alphabetical order ( collating sequence ). The main deviations in ASCII order are: An intermediate order converts uppercase letters to lowercase before comparing ASCII values. ASCII reserves

1440-541: A reserved meaning. Over time this interpretation has been co-opted and has eventually been changed. In modern usage, an ESC sent to the terminal usually indicates the start of a command sequence, which can be used to address the cursor, scroll a region, set/query various terminal properties, and more. They are usually in the form of a so-called " ANSI escape code " (often starting with a " Control Sequence Introducer ", "CSI", " ESC [ ") from ECMA-48 (1972) and its successors. Some escape sequences do not have introducers, like

1536-498: A series of keys to be typed, like a recording to play back. Thus, they cannot loop or branch unless they input such code into the BASIC interpreter. As well as being used during a reset, they can be executed at any time with the operating system's *EXEC command. EXEC files are file system independent. There was a variant of the DFS called the DNFS, or Disc/Network Filing System, that contained

1632-404: A seven-bit code. The committee considered an eight-bit code, since eight bits ( octets ) would allow two four-bit patterns to efficiently encode two digits with binary-coded decimal . However, it would require all data transmission to send eight bits when seven could suffice. The committee voted to use a seven-bit code to minimize costs associated with data transmission. Since perforated tape at

1728-399: 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 end-of-file , was used colloquially and conventionally as a three-letter acronym for control-Z instead of SUBstitute. The end-of-text character ( ETX ), also known as control-C , was inappropriate for

1824-446: A variety of reasons, while using control-Z as the control character to end a file is analogous to the letter Z's position at the end of the alphabet, and serves as a very convenient mnemonic aid . A historically common and still prevalent convention uses the ETX character convention to interrupt and halt a program via an input data stream, usually from a keyboard. The Unix terminal driver uses

1920-481: A venture capitalist and entrepreneur. The award was presented at the annual European Electronics Industry Awards in London. Hauser was awarded an Honorary CBE for "innovative service to the UK enterprise sector" in 2001. In 1998, Hauser was elected into an honorary fellowship of Hughes Hall, Cambridge , and he was also elected into an honorary fellowship of King's College, Cambridge with effect from 1 January 2000. In

2016-731: Is 0101 in binary). Many of the non-alphanumeric characters were positioned to correspond to their shifted position on typewriters; an important subtlety is that these were based on mechanical typewriters, not electric typewriters. Mechanical typewriters followed the de facto standard set by the Remington No. 2 (1878), the first typewriter with a shift key, and the shifted values of 23456789- were "#$ %_&'()  – early typewriters omitted 0 and 1 , using O (capital letter o ) and l (lowercase letter L ) instead, but 1! and 0) pairs became standard once 0 and 1 became common. Thus, in ASCII !"#$ % were placed in

SECTION 20

#1733093088638

2112-451: Is flat and a default directory of $ is used instead of a root directory. On requesting a catalogue of the disc (with the *CAT or *. commands), files in the current directory are shown with no directory prefix in one block, and below that are listed all other files in a second block, with their directory prefixes visible. For example, (from Acorn DFS - third party DFS implementations may vary slightly): The top seven files are all in

2208-464: Is in) is limited to 31. In the interests of saving space, the most significant bit of the directory letter for a file is used as the locked (read-only) flag. Although physical disks are usually formatted as either 100 KB or 200 KB, DFS supports volume sizes up to 256 KB. The largest DFS file size allowed is the volume size minus ½ KB for the catalogue, as file sizes are stored as an 18-bit quantity. The DFS does not support data fragmentation , meaning

2304-566: Is limited by the choice of the Intel 8271 controller in the original BBC Micro, which only supports FM encoding, not the MFM encoding which was already in common use by the time of the BBC Micro's launch. FM encoding gives half the recording capacity of MFM for a given physical disc density. FM and MFM encoding are commonly referred to as "single density" and "double density", although the discs and drives are

2400-528: Is present in all Acorn machines supplied with 3½" drives. As of 2009, 3½" drives are more commonly used with BBC Micros than in the past, including use with DFS, due to their greater availability and easier data interchange with more recent computers. High-density 5¼" and 3½" discs are not supported by DFS. The DFS does not directly support double-sided discs; instead, the two heads of a double-sided drive are treated as two separate logical drives. The DFS can support up to four volumes, numbered from 0 to 3. Drive 0

2496-427: 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 its typehead backwards, so it did not have a key on its keyboard to send

2592-543: Is space on the disc. In contrast the *COMPACT command uses program memory as a buffer to relocate the files, overwriting any program and data in memory. Like the cassette filing system, the Acorn DFS supports the BBC Micro's standard file metadata: load address and execution address, required because Acorn MOS (the operating system used by the BBC Micro) does not support relocation of binary code. A file should be loaded to

2688-490: Is stored as a sector count in the catalogue on track zero. Track zero is located in the same place on both 40- and 80-track discs, allowing a disc file system to set the motor stepping accordingly. However, the Intel 8271-based Acorn DFS does not do so, and so dual-format capability was addressed in a number of ways: Failure to use the correct setting would result in errors from the DFS such as Disk fault 18 at 01/00 , or damage to

2784-404: Is the newline problem on various operating systems . 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 typewriter the carriage holding the paper moves while

2880-462: Is the working directory on the current volume, much like the working directory on any other command line system. The "library" is a second, alternative working directory that functions more like PATH and had the benefit of being able to be on any volume. Requests to open files with unqualified names, will first be searched for in the working directory; failing this, the library directory will also be searched. The directory and library both default to

2976-404: Is the default with drive 1 representing a second drive attached to the cable. "Drive" 2 referred to the reverse side of drive 0, and "drive" 3 was the reverse of drive 1. There is no support for more than two physical drives. Due to the installed base of single-sided drives, commercial software was normally provided on single-sided discs, or as " flippy discs " that were manually reversed to access

Disc Filing System - Misplaced Pages Continue

3072-486: The Comité Consultatif International Téléphonique et Télégraphique (CCITT) International Telegraph Alphabet No. 2 (ITA2) standard of 1932, FIELDATA (1956 ), and early EBCDIC (1963), more than 64 codes were required for ASCII. ITA2 was in turn based on Baudot code , the 5-bit telegraph code Émile Baudot invented in 1870 and patented in 1874. The committee debated the possibility of

3168-618: The Teletype Model 33 , which used the left-shifted layout corresponding to ASCII, differently from traditional mechanical typewriters. Electric typewriters, notably the IBM Selectric (1961), used a somewhat different layout that has become de facto standard on computers – following the IBM PC (1981), especially Model M (1984) – and thus shift values for symbols on modern keyboards do not correspond as closely to

3264-697: The United States Federal Government support ASCII, stating: I have also approved recommendations of the Secretary of Commerce [ Luther H. Hodges ] regarding standards for recording the Standard Code for Information Interchange on magnetic tapes and paper tapes when they are used in computer operations. All computers and related equipment configurations brought into the Federal Government inventory on and after July 1, 1969, must have

3360-667: The carriage return , line feed , and tab codes. For example, lowercase i would be represented in the ASCII encoding by binary 1101001 = hexadecimal 69 ( i is the ninth letter) = decimal 105. Despite being an American standard, ASCII does not have a code point for the cent (¢). It also does not support English terms with diacritical marks such as résumé and jalapeño , or proper nouns with diacritical marks such as Beyoncé (although on certain devices characters could be combined with punctuation such as Tilde (~) and Backtick (`) to approximate such characters.) The American Standard Code for Information Interchange (ASCII)

3456-641: The "Reset to Initial State", "RIS" command " ESC c ". In contrast, an ESC read from the terminal is most often used as an out-of-band character used to terminate an operation or special mode, as in the TECO and vi text editors . In graphical user interface (GUI) and windowing systems, ESC generally causes an application to abort its current operation or to exit (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

3552-574: The "help" prefix command in GNU Emacs . Many more of the control characters have been assigned meanings quite different from their original ones. The "escape" character (ESC, code 27), for example, was intended originally to allow sending of other control characters as literals instead of invoking their meaning, an "escape sequence". This is the same meaning of "escape" encountered in URL encodings, C language strings, and other systems where certain characters have

3648-401: The "line feed" function (which causes a printer to advance its paper), and character 8 represents " backspace ". RFC   2822 refers to control characters that do not include carriage return, line feed or white space as non-whitespace control characters. Except for the control characters that prescribe elementary line-oriented formatting, ASCII does not define any mechanism for describing

3744-419: The ASCII chart in this article. 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 , and punctuation symbols . In addition, the original ASCII specification included 33 non-printing control codes which originated with Teletype models ; most of these are now obsolete, although a few are still commonly used, such as

3840-676: The ASCII table as earlier keyboards did. The /? pair also dates to the No. 2, and the ,< .> pairs were used on some keyboards (others, including the No. 2, did not shift , (comma) or . (full stop) so they could be used in uppercase without unshifting). However, ASCII split the ;: pair (dating to No. 2), and rearranged mathematical symbols (varied conventions, commonly -* =+ ) to :* ;+ -= . Some then-common typewriter characters were not included, notably ½ ¼ ¢ , while ^ ` ~ were included as diacritics for international use, and < > for mathematical use, together with

3936-453: The Acorn 1770 DFS, which used the same disc format as the earlier version but added a set of extra commands and supported the improved WD1770 floppy drive controller chip. DFS conventionally uses one side of a double-density 5¼" floppy disc . Discs are formatted as either 40 or 80 track, giving a capacity of 100 or 200 KB per side (ten 256-byte sectors per track, with FM encoding). The capacity

Disc Filing System - Misplaced Pages Continue

4032-544: The Acorn DFS from the System 2 without assistance from Acorn as they had no resources available. This required some minor hardware and software changes to make the DFS compatible with the BBC Micro. Barson won the tenders for both states, with the DFS fitted, a year ahead of the UK. It was this early initiative that resulted in the BBC Micro being more heavily focused on the education market in Australia, with very little penetration of

4128-495: The BBC Micro defaulting to caps lock being enabled after a hard or soft reset. The character set is quite permissive, and all printable characters of 7-bit ASCII are allowed, including spaces, but excluding: For the sake of portability to third-party DFS implementations, it is best to avoid : and . in leaf names. Quotation marks are allowed, although BBC BASIC requires them to be escaped twice: A fully qualified filename, or "file specification" ("fsp" for short) contains

4224-467: The DEL character was assigned to erase the previous character. Because of this, DEC video terminals (by default) sent the DEL character for the key marked "Backspace" while the separate key marked "Delete" sent an escape sequence ; many other competing terminals sent a BS character for the backspace key. The early Unix tty drivers, unlike some modern implementations, allowed only one character to be set to erase

4320-632: The Econet Network Filing System (NFS), standard Disc Filing System and Tube co-processor support software on a single ROM; this ROM installed two filing systems into the OS at once. The initial design for the DFS was based around an Intel Corporation FDC 8271 disc drive controller, the immediate predecessor of the 8272 design found in the IBM Personal Computer . The 8271 controller was of limited functionality and obsolete, and later versions of

4416-462: 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 ( delete ) 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

4512-551: The UK. Publication of the report in 2010 led to the establishment of Catapult centres with £200 million of government funding. He was co-founder of ARM Holdings, the Cambridge-based microchip manufacturer that was bought in 2016 by Japan's SoftBank. Since 2015, he is actively supporting Austrian start-ups and technology companies. In particular, he has invested in 2017 in the MEMS-speaker start-up "USound" and in eyeson,

4608-711: The US and Europe. In 1986, Hauser co-founded the Olivetti Research Laboratory (ORL) in Cambridge with Andy Hopper , who became the laboratory's director. Hauser's role in Acorn was portrayed by Edward Baker-Duly in the BBC drama Micro Men . In 1988, Hauser left Olivetti to start the Active Book Company, investing £1 million of his own money. The company sought to develop a portable ARM-based microcomputer "the size of

4704-504: The address the programmer intended, as the contents may refer to internal locations by absolute addresses. An execution address is also recorded as the entry point is not necessarily at the beginning, or even within the file. File attributes are limited to a single bit: Locked. When set, an L appears to the right of the file's name in the catalogue and the file may not be altered, overwritten or deleted. DFS discs do not track any dates (because Acorn MOS prior to version 3 did not maintain

4800-656: The board of Red-M (Communications) Ltd. He holds honorary doctorates from the Universities of Bath and Loughborough and from Anglia Ruskin University . He is a member of the advisory board on the Higher Education Innovation Fund, and of the UK's Council for Science and Technology . Hauser was commissioned by the Department for Business, Innovation and Skills to write a report on technology and innovation in

4896-585: The change into its draft standard. The X3.2.4 task group voted its approval for the change to ASCII at its May 1963 meeting. Locating the lowercase letters in sticks 6 and 7 caused the characters to differ in bit pattern from the upper case by a single bit, which simplified case-insensitive character matching and the construction of keyboards and printers. The X3 committee made other changes, including other new characters (the brace and vertical bar characters), renaming some control characters (SOM became start of header (SOH)) and moving or removing others (RU

SECTION 50

#1733093088638

4992-644: The company was seeking application developers for the platform. The Active Book was intended to cost around $ 2,000, provide eight to ten hours of battery life, and was to run the Helios operating system . Not wanting to repeat the mistakes made by Acorn, which had kept its technology to itself, he demonstrated the Active Book to as many large companies as he could. AT&T Corporation acquired Active Book in July 1991 and incorporated it into their EO Personal Communicator , which

5088-600: The company was sold to Illumina, Inc of San Diego in January 2007 for over $ US600 million. In 2009, Hauser was announced as the first customer of the Illumina Personal Genome Sequencing service. As of 2009, Hauser is the head of the East Anglia Stem Cell research network. Hauser is a non-executive director of Cambridge Display Technology , a non-executive director of XMOS Ltd and a member of

5184-493: The concept of "carriage return" was meaningless. IBM's PC DOS (also marketed as MS-DOS by Microsoft) inherited the convention by virtue of being loosely based on CP/M, and Windows in turn inherited it from MS-DOS. Requiring two characters to mark the end of a line introduces unnecessary complexity and ambiguity as to how to interpret each character when encountered by itself. To simplify matters, plain text data streams, including files, on Multics used line feed (LF) alone as

5280-524: The convention was so well established that backward compatibility necessitated continuing to follow it. When Gary Kildall created CP/M , he was inspired by some of the command line interface conventions used in DEC's RT-11 operating system. Until the introduction of PC DOS in 1981, IBM had no influence in this because their 1970s operating systems used EBCDIC encoding instead of ASCII, and they were oriented toward punch-card input and line printer output on which

5376-416: The current directory which is $ on drive 0. Below that are all the files in other directories, in this case A , B and F . An L after a filename (as with A.HELLO , above) shows the file is locked against modification or deletion. The first line contains the disc title and the modification count. The DFS provides a working space, divided up into the directory and the library. The "directory"

5472-412: The disc drive by trying to step the heads beyond the physical end of the disc surface. Switching to 80 tracks did not extend the catalogue in any way, leaving the user prone to running out of filename slots before running out of space on the disc. This situation resulted in a Cat full error. DFS is case-preserving but not case-sensitive. The prevalence of all-capitals filenames is most likely due to

5568-659: The earlier five-bit ITA2 , which was also used by the competing Telex teleprinter system. Bob Bemer introduced features such as the escape sequence . His British colleague Hugh McGregor Ross helped to popularize this work – according to Bemer, "so much so that the code that was to become ASCII was first called the Bemer–Ross Code in Europe". Because of his extensive work on ASCII, Bemer has been called "the father of ASCII". On March 11, 1968, US President Lyndon B. Johnson mandated that all computers purchased by

5664-576: The earlier teleprinter encoding systems. Like other character encodings , ASCII specifies a correspondence between digital bit patterns and character symbols (i.e. graphemes and control characters ). This allows digital devices to communicate with each other and to process, store, and communicate character-oriented information such as written language. Before ASCII was developed, the encodings in use included 26 alphabetic characters, 10 numerical digits , and from 11 to 25 special graphic symbols. To include all these, and control characters compatible with

5760-544: The end-of-transmission character ( EOT ), also known as control-D, to indicate the end of a data stream. In the C programming language , and in Unix conventions, the null character is used to terminate text strings ; such null-terminated strings can be known in abbreviation as ASCIZ or ASCIIZ, where here Z stands for "zero". Other representations might be used by specialist equipment, for example ISO 2047 graphics or hexadecimal numbers. Codes 20 hex to 7E hex , known as

5856-444: The failure occurs at the sector allocation stage, the error returned is Disk full . The *COMPACT command is provided to relocate all files on disc to a solid block, placing all the free space after it in a second block. This allows the next file created to fill the disc, but only the last existing file can be extended without being moved. SAVE deletes any existing file and copies the specified block of memory to wherever there

SECTION 60

#1733093088638

5952-489: The file system from various vendors including Solidisk, Acorn and Watford Electronics were based on the later WD1770 and WD1772 drive controllers. The 1770 controller quickly became the standard controller in the Acorn range following the advent of ADFS. The DFS was superseded by the Advanced Disc Filing System (ADFS) which was fully hierarchical and was suitable for running hard drives on the BBC Micro. The ADFS

6048-624: The first 32 code points (numbers 0–31 decimal) and the last one (number 127 decimal) for control characters . These are codes intended to control peripheral devices (such as printers ), or to provide meta-information about data streams, such as those stored on magnetic tape. Despite their name, these code points do not represent printable characters (i.e. they are not characters at all, but signals). For debugging purposes, "placeholder" symbols (such as those given in ISO 2047 and its predecessors) are assigned to them. For example, character 0x0A represents

6144-507: The home computer market until the arrival of the Acorn Electron . The DFS shipped as a ROM and Disk Controller Chip fitted to the BBC Micro's motherboard. The filing system was of extremely limited functionality and storage capability, using a flat directory structure. Each filename can be up to seven letters long, plus one letter for the directory in which the file is stored. The DFS is remarkable in that unlike most filing systems, there

6240-448: The keytop for the O key also showed a left-arrow symbol (from ASCII-1963, which had this character instead of underscore ), 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

6336-564: The launch of the BBC Micro . In 2001, Hauser became an Honorary Doctor at Anglia Ruskin University . On 8 July 2002, Hauser was elected a Fellow of the Institute of Physics (FInstP) and an International Fellow of the Royal Academy of Engineering (FREng). In May 2004 he presented the prestigious IEE Pinkerton Lecture . In 2005, Hauser received a Lifetime Achievement Award for his work as

6432-776: The local conventions and the NVT. The File Transfer Protocol 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

6528-505: The machine is soft or hard reset, the DFS checks drive 0 for a disc containing a positive boot flag. The boot flag is either 0 (ignore), 1 (load file), 2 (run machine code file) or 3 ("execute" script). If the boot flag is positive, a file called $ .!BOOT is looked for and loaded into memory (1), loaded and executed as machine code (2) or fed into the keyboard buffer (3). Option 3 reads "EXEC" files, text macro files used as primitive shell scripts . These are not true shell scripts but simply

6624-498: The other side. Discs can be formatted using 40 or 80 tracks, using the *FORM40 or *FORM80 commands, and drives can be either 40 or 80 track. This is the most common compatibility issue for DFS users: 40-track discs were the norm for commercial software distribution, due to the installed base of 40-track drives, but 80-track drives became more common as prices dropped, allowing users to store more data. An 80-track drive will not automatically read 40-track discs. The disc capacity

6720-452: The previous character in canonical input processing (where a very simple line editor is available); this could be set to BS or DEL, but not both, resulting in recurring situations of ambiguity where users had to decide depending on what terminal they were using ( shells that allow line editing, such as ksh , bash , and zsh , understand both). The assumption that no key sent a BS character allowed Ctrl+H to be used for other purposes, such as

6816-515: The previous section. Code 7F hex corresponds to the non-printable "delete" (DEL) control character and is therefore omitted from this chart; it is covered in the previous section's chart. Earlier versions of ASCII used the up arrow instead of the caret (5E hex ) and the left arrow instead of the underscore (5F hex ). ASCII was first used commercially during 1963 as a seven-bit teleprinter code for American Telephone & Telegraph 's TWX (TeletypeWriter eXchange) network. TWX originally used

6912-413: The printable characters, represent letters, digits, punctuation marks , and a few miscellaneous symbols. There are 95 printable characters in total. Code 20 hex , the "space" character, denotes the space between words, as produced by the space bar of a keyboard. Since the space character is considered an invisible graphic (rather than a control character) it is listed in the table below instead of in

7008-444: 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. The use of ASCII format for Network Interchange was described in 1969. That document was formally elevated to an Internet Standard in 2015. Originally based on the (modern) English alphabet , ASCII encodes 128 specified characters into seven-bit integers as shown by

7104-443: The same directory. The catalogue (file table) occupies the first two disc sectors: one for the names and directories of each file, and a matching sector holding the file locations, sizes and metadata. Eight bytes of each sector are used for each file. With a further eight bytes from each sector reserved for the 12-byte disc title and the volume information, the total number of files on the disc (irrespective of which directory each file

7200-516: The same reason, many special signs commonly used as separators were placed before digits. The committee decided it was important to support uppercase 64-character alphabets , and chose to pattern ASCII so it could be reduced easily to a usable 64-character set of graphic codes, as was done in the DEC SIXBIT code (1963). Lowercase letters were therefore not interleaved with uppercase . To keep options available for lowercase letters and other graphics,

7296-735: The same year he was awarded the Mountbatten Medal . Hauser was elected a Fellow of the Royal Society (FRS) in 2012. His nomination reads: Distinguished as a science-based innovator and serial-entrepreneur whose ventures have been at the forefront of UK innovation. A major contributor to the global technology and growth agendas and an influential member of senior policy making bodies. An inspiration and role-model for generations of entrepreneurs who has been directly involved in many companies, providing enthusiasm, mentoring, and financing leading to technology based wealth creation at scale. Hauser

7392-420: The same, unlike "high density", which uses different drives and discs. Double-density 3½" discs can be formatted and used with 1770 DFS (the Intel 8271-based DFS has problems with many 3½" drives), giving the same "single-density" capacity with FM encoding, but this was not originally standard practice. 3½" discs were normally formatted as MFM "double density" using the later Advanced Disc Filing System , as this

7488-494: The second stick, positions 1–5, corresponding to the digits 1–5 in the adjacent stick. The parentheses could not correspond to 9 and 0 , however, because the place corresponding to 0 was taken by the space character. This was accommodated by removing _ (underscore) from 6 and shifting the remaining characters, which corresponded to many European typewriters that placed the parentheses with 8 and 9 . This discrepancy from typewriters led to bit-paired keyboards , notably

7584-534: The simple line characters \ | (in addition to common / ). The @ symbol was not used in continental Europe and the committee expected it would be replaced by an accented À in the French variation, so the @ was placed in position 40 hex , right before the letter A. The control codes felt essential for data transmission were the start of message (SOM), end of address (EOA), end of message (EOM), end of transmission (EOT), "who are you?" (WRU), "are you?" (RU),

7680-402: The special and numeric codes were arranged before the letters, and the letter A was placed in position 41 hex to match the draft of the corresponding British standard. The digits 0–9 are prefixed with 011, but the remaining 4 bits correspond to their respective values in binary, making conversion with binary-coded decimal straightforward (for example, 5 in encoded to 011 0101 , where 5

7776-425: The standard is unclear about the meaning of "delete". Probably the most influential single device affecting the interpretation of these characters was the Teletype Model 33 ASR, which was a printing terminal with an available paper tape 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,

7872-440: The structure or appearance of text within a document. Other schemes, such as markup languages , 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 data stream , and sometimes accidental, for example

7968-511: The syntax of computer languages and text markup. ASCII hugely influenced the design of character sets used by modern computers, including Unicode which has over a million code points, but the first 128 of these are the same as ASCII. The Internet Assigned Numbers Authority (IANA) prefers the name US-ASCII for this character encoding. ASCII is one of the IEEE milestones . ASCII was developed in part from telegraph code . Its first commercial use

8064-441: The tape reader to stop; receiving control-Q (XON, transmit on) caused the tape reader to resume. This so-called flow control technique became adopted by several early computer operating systems as a "handshaking" signal warning a sender to stop transmission because of impending buffer 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

8160-600: The time could record eight bits in one position, it also allowed for a parity bit for error checking if desired. Eight-bit machines (with octets as the native data type) that did not use parity checking typically set the eighth bit to 0. The code itself was patterned so that most control codes were together and all graphic codes were together, for ease of identification. The first two so-called ASCII sticks (32 positions) were reserved for control characters. The "space" character had to come before graphics to make sorting easier, so it became position 20 hex ; for

8256-447: The typebars that strike the ribbon remain stationary. The entire carriage had to be pushed (returned) to the right in order to position the paper for the next line. DEC operating systems ( OS/8 , RT-11 , RSX-11 , RSTS , TOPS-10 , etc.) used both characters to mark the end of a line so that the console device (originally Teletype machines) would work. By the time so-called "glass TTYs" (later called CRTs or "dumb terminals") came along,

8352-654: Was 16 he went to the United Kingdom to learn English at a language school in Cambridge . After a master's degree in physics from Vienna University , he returned to King's College, Cambridge to do a PhD in physics at the Cavendish Laboratory . Hauser is probably best known for his part in setting up Acorn Computers with Chris Curry in 1978. When Olivetti took control of Acorn in 1985 he became vice-president for research at Olivetti, in charge of laboratories in

8448-704: Was developed under the auspices of a committee of the American Standards Association (ASA), called the X3 committee, by its X3.2 (later X3L2) subcommittee, and later by that subcommittee's X3.2.4 working group (now INCITS ). The ASA later became the United States of America Standards Institute (USASI) and ultimately became the American National Standards Institute (ANSI). With the other special characters and control codes filled in, ASCII

8544-694: Was elected a Distinguished Fellow of the British Computer Society (DFBCS) in 2013 recognising his contribution to computing science in the UK. ASCII ASCII ( / ˈ æ s k iː / ASS -kee ), an acronym for American Standard Code for Information Interchange , is a character encoding standard for electronic communication. 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

8640-523: Was founded, with Hauser as chairman. On 14 June 2001, the Hauser-Raspe Foundation was registered as a charity to advance education, by Hauser and his wife Pamela Raspe. In August 2004, Amadeus Capital Partners led the Series B venture capital financing of Solexa, and Hauser joined its board of directors. Solexa developed a next-generation DNA sequencing technology which became the market leader;

8736-554: Was in the Teletype Model 33 and the Teletype Model 35 as a seven- bit teleprinter code promoted by Bell data services. Work on the ASCII standard began in May 1961, with the first meeting of the American Standards Association's (ASA) (now the American National Standards Institute 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,

8832-411: Was no single vendor or implementation. The original DFS was written by Acorn, who continued to maintain their own codebase, but various disc drive vendors wrote their own implementations. Companies who wrote their own DFS implementations included Cumana, Solidisk, Opus and Watford Electronics . The Watford Electronics implementation is notable for supporting 62 files per disc instead of the usual 31, using

8928-676: Was published as ASA X3.4-1963, leaving 28 code positions without any assigned meaning, reserved for future standardization, and one unassigned control code. There was some debate at the time whether there should be more control characters rather than the lowercase alphabet. The indecision did not last long: during May 1963 the CCITT Working Party on the New Telegraph Alphabet proposed to assign lowercase characters to sticks 6 and 7, and International Organization for Standardization TC 97 SC 2 voted during October to incorporate

9024-553: Was released in April 1993. Hauser became chief technical officer and chairman of EO Europe. Sales did not meet expectations, and AT&T's EO subsidiary folded on 29 July 1994. In 1990, Hauser was involved in spinning out Advanced RISC Machines (ARM) from Acorn. In 1993, Hauser set up Advanced Telecommunication Modules Ltd with Andy Hopper. The company was acquired by Conexant Systems on 1 March 2004. He founded NetChannel Ltd in June 1996 as

9120-450: Was removed). ASCII was subsequently updated as USAS X3.4-1967, then USAS X3.4-1968, ANSI X3.4-1977, and finally, ANSI X3.4-1986. In the X3.15 standard, the X3 committee also addressed how ASCII should be transmitted ( least significant bit first) and recorded on perforated tape. They proposed a 9-track standard for magnetic tape and attempted to deal with some punched card formats. The X3.2 subcommittee designed ASCII based on

9216-559: Was the default filing system on the BBC Master but most users are likely to have reverted to the DFS for compatibility reasons; ADFS could not read DFS discs. The ADFS was also chosen as the standard filing system for RISC OS . Hermann Hauser Hermann Maria Hauser (born 1948 ) is an Austrian entrepreneur, venture capitalist and inventor who is primarily associated with the Cambridge technology community in England. When Hauser

#637362