Early research and development:
119-476: Merging the networks and creating the Internet: Commercialization, privatization, broader access leads to the modern Internet: Examples of Internet services: UUCP ( Unix-to-Unix Copy ) is a suite of computer programs and protocols allowing remote execution of commands and transfer of files , email and netnews between computers . A command named uucp is one of
238-507: A computer terminal (until the 1990s) to a graphical user interface (GUI) computer. Computer terminals limited programmers to a single shell running in a command-line environment . During the 1970s, full-screen source code editing became possible through a text-based user interface . Regardless of the technology available, the goal is to program in a programming language . Programming language features exist to provide building blocks to be combined to express programming ideals. Ideally,
357-446: A digital modem – one that connects directly to a digital telephone network interface, such as T1 or PRI – could send a signal that utilized every bit of bandwidth available in the system. While that signal still had to be converted back to analog at the subscriber end, that conversion would not distort the signal in the same way that the opposite direction did. The first 56k (56 kbit/s) dial-up option
476-462: A list of integers could be called integer_list . In object-oriented jargon, abstract datatypes are called classes . However, a class is only a definition; no memory is allocated. When memory is allocated to a class and bound to an identifier , it is called an object . Object-oriented imperative languages developed by combining the need for classes and the need for safe functional programming . A function, in an object-oriented language,
595-532: A stored-program computer loads its instructions into memory just like it loads its data into memory. As a result, the computer could be programmed quickly and perform calculations at very fast speeds. Presper Eckert and John Mauchly built the ENIAC. The two engineers introduced the stored-program concept in a three-page memo dated February 1944. Later, in September 1944, John von Neumann began working on
714-523: A 16-bit checksum of the payload, not including the header. The next byte is the data type and finally, the last byte is the XOR of the header, allowing it to be checked separately from the payload. The control byte consists of three bit-fields in the format TTXXXYYY. TT is the packet type, 0 for control packets (which also requires K=9 to be valid), 1 for alternate data (not used in UUCP), 2 for data, and 3 indicates
833-401: A color display and keyboard that was packaged in a single console. The disk operating system was programmed using IBM's Basic Assembly Language (BAL) . The medical records application was programmed using a BASIC interpreter. However, the computer was an evolutionary dead-end because it was extremely expensive. Also, it was built at a public university lab for a specific purpose. Nonetheless,
952-500: A few phone calls to the administrators of prospective neighbor systems. Neighbor systems were often close enough to avoid all but the most basic charges for telephone calls. uux is remote command execution over UUCP. The uux command is used to execute a command on a remote system , or to execute a command on the local system using files from remote systems. The command is run by the uucico daemon, which handles remote execution requests as simply another kind of file to batch-send to
1071-529: A form such as …!bigsite!foovax!barbox!user . This directs people to route their mail to machine bigsite (presumably a well-known and well-connected machine accessible to everybody) and from there through the machine foovax to the account of user user on barbox . Publishing a full path would be pointless, because it would be different, depending on where the sender was. (e.g. Ann at one site may have to send via path gway!tcol!canty!uoh!bigsite!foovax!barbox!user , whereas from somewhere else, Bill has to send via
1190-408: A given unit of time , usually expressed in bits per second (symbol bit/s , sometimes abbreviated "bps") or rarely in bytes per second (symbol B/s ). Modern broadband modem speeds are typically expressed in megabits per second (Mbit/s). Historically, modems were often classified by their symbol rate , measured in baud . The baud unit denotes symbols per second, or the number of times per second
1309-509: A major contributor. The statements were English-like and verbose. The goal was to design a language so managers could read the programs. However, the lack of structured statements hindered this goal. COBOL's development was tightly controlled, so dialects did not emerge to require ANSI standards. As a consequence, it was not changed for 15 years until 1974. The 1990s version did make consequential changes, like object-oriented programming . ALGOL (1960) stands for "ALGOrithmic Language". It had
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#17327723681071428-518: A medium with less than ideal characteristics, such as a telephone line that is of poor quality or is too long. This capability is often adaptive so that a modem can discover the maximum practical transmission rate during the connect phase, or during operation. Modems grew out of the need to connect teleprinters over ordinary phone lines instead of the more expensive leased lines which had previously been used for current loop –based teleprinters and automated telegraphs . The earliest devices which satisfy
1547-515: A number of new link layer protocols. These newer connections also reduced the need for UUCP at all, as newer application protocols developed to take advantage of the new networks. Today, UUCP is rarely used over dial-up links, but is occasionally used over TCP/IP . The number of systems involved, as of early 2006, ran between 1500 and 2000 sites across 60 enterprises. UUCP's longevity can be attributed to its low cost, extensive logging, native failover to dialup, and persistent queue management. UUCP
1666-548: A process. The interpreter then loads the source code into memory to translate and execute each statement . Running the source code is slower than running an executable . Moreover, the interpreter must be installed on the computer. The "Hello, World!" program is used to illustrate a language's basic syntax . The syntax of the language BASIC (1964) was intentionally limited to make the language easy to learn. For example, variables are not declared before being used. Also, variables are automatically initialized to zero. Here
1785-521: A profound influence on programming language design. Emerging from a committee of European and American programming language experts, it used standard mathematical notation and had a readable, structured design. Algol was first to define its syntax using the Backus–Naur form . This led to syntax-directed compilers. It added features like: Algol's direct descendants include Pascal , Modula-2 , Ada , Delphi and Oberon on one branch. On another branch
1904-466: A programming language should: The programming style of a programming language to provide these building blocks may be categorized into programming paradigms . For example, different paradigms may differentiate: Each of these programming styles has contributed to the synthesis of different programming languages . A programming language is a set of keywords , symbols , identifiers , and rules by which programmers can communicate instructions to
2023-476: A series of file requests. There are four types: After sending an H command, the calling system sends a final packet \20OOOOOO\0 (control-P, six ohs, null-terminator) and the called system responds with \20OOOOOO\0 (control-P, seven ohs, null-terminator). Some systems will simply hang up on the successful reception of the H command and not bother with the final handshake. Within the suite of protocols in UUCP,
2142-601: A series of popular modems for the S-100 bus and Apple II computers that could directly dial out, answer incoming calls, and hang up entirely from software, the basic requirements of a bulletin board system (BBS). The seminal CBBS for instance was created on an S-100 machine with a Hayes internal modem, and a number of similar systems followed. Echo cancellation became a feature of modems in this period, which allowed both modems to ignore their own reflected signals. This way both modems can simultaneously transmit and receive over
2261-404: A short packet that re-defines the meaning of K. In a data packet, XXX is the packet number for this packet from 0 to 7, and YYY is the last that was received correctly. This provides up to 8 packets in a window. In a control packet, XXX indicates the command and YYY is used for various parameters. For instance, transfers are started by sending a short control packet with TT=0 (control), XXX=7 and YYY
2380-609: A single set of files describing all connections in the network. These files were then published monthly in a newsgroup dedicated to this purpose. The UUCP map files could then be used by software such as "pathalias" to compute the best route path from one machine to another for mail, and to supply this route automatically. The UUCP maps also listed contact information for the sites, and so gave sites seeking to join UUCPNET an easy way to find prospective neighbors. Many UUCP hosts, particularly those at universities, were also connected to
2499-494: A syntax that would likely fail IBM's compiler. The American National Standards Institute (ANSI) developed the first Fortran standard in 1966. In 1978, Fortran 77 became the standard until 1991. Fortran 90 supports: COBOL (1959) stands for "COmmon Business Oriented Language". Fortran manipulated symbols. It was soon realized that symbols did not need to be numbers, so strings were introduced. The US Department of Defense influenced COBOL's development, with Grace Hopper being
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#17327723681072618-745: A system using 4k packets and 7 packet windows (4096x7) would offer performance matching or beating the best file-transfer protocols like ZMODEM . In practice, many implementations only supported a single setting of 64x3. As a result, the g-protocol has an undeserved reputation for poor performance. Confusion over the packet and window sizes led to the G-protocol, differing only in that it always used 4096x3. Taylor UUCP did not support G, but did support any valid requested window or packet size, so remote systems starting G would work fine with Taylor's g, while two Taylor systems could negotiate even faster connections. Telebit modems used protocol spoofing to improve
2737-474: A technological improvement to refine the production of field-effect transistors (1963). The goal is to alter the electrical resistivity and conductivity of a semiconductor junction . First, naturally occurring silicate minerals are converted into polysilicon rods using the Siemens process . The Czochralski process then converts the rods into a monocrystalline silicon , boule crystal . The crystal
2856-546: Is an example computer program, in Basic, to average a list of numbers: Once the mechanics of basic computer programming are learned, more sophisticated and powerful languages are available to build large computer systems. Improvements in software development are the result of improvements in computer hardware . At each stage in hardware's history, the task of computer programming changed dramatically. In 1837, Jacquard's loom inspired Charles Babbage to attempt to build
2975-418: Is assigned to a class. An assigned function is then referred to as a method , member function , or operation . Object-oriented programming is executing operations on objects . Object-oriented languages support a syntax to model subset/superset relationships. In set theory , an element of a subset inherits all the attributes contained in the superset. For example, a student is a person. Therefore,
3094-453: Is called source code . Source code needs another computer program to execute because computers can only execute their native machine instructions . Therefore, source code may be translated to machine instructions using a compiler written for the language. ( Assembly language programs are translated using an assembler .) The resulting file is called an executable . Alternatively, source code may execute within an interpreter written for
3213-442: Is known as the x86 series . The x86 assembly language is a family of backward-compatible machine instructions . Machine instructions created in earlier microprocessors were retained throughout microprocessor upgrades. This enabled consumers to purchase new computers without having to purchase new application software . The major categories of instructions are: VLSI circuits enabled the programming environment to advance from
3332-438: Is near the theoretical Shannon limit of a phone line. While 56 kbit/s speeds had been available for leased-line modems for some time, they did not become available for dial up modems until the late 1990s. In the late 1990s, technologies to achieve speeds above 33.6 kbit/s began to be introduced. Several approaches were used, but all of them began as solutions to a single fundamental problem with phone lines. By
3451-461: Is normally started by having a user log into the target system and then running the UUCP program. In most cases, this is automated by logging into a known user account used for transfers, whose account's shell has been set to uucico . Thus, for automated transfers, another machine simply has to open a modem connection to the called machine and log into the known account. When uucico runs, it will expect to receive commands from another UUCP program on
3570-627: Is the chat file format, largely inherited by the Expect software package. UUCP was in use over special-purpose high cost links (e.g. marine satellite links) long after its disappearance elsewhere, and still remains in legacy use. In addition to legacy use, in 2021 new and innovative UUCP uses are growing, especially for telecommunications in the HF band, for example, for communities in the Amazon rainforest for email exchange and other uses. A patch to Ian's UUCP
3689-427: Is then thinly sliced to form a wafer substrate . The planar process of photolithography then integrates unipolar transistors, capacitors , diodes , and resistors onto the wafer to build a matrix of metal–oxide–semiconductor (MOS) transistors. The MOS transistor is the primary component in integrated circuit chips . Originally, integrated circuit chips had their function set during manufacturing. During
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3808-695: The new statement. A module's other file is the source file . Here is a C++ source file for the GRADE class in a simple school application: Here is a C++ header file for the PERSON class in a simple school application: Modems A modulator-demodulator , commonly referred to as a modem , is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by modulating one or more carrier wave signals to encode digital information , while
3927-510: The Analytical Engine . The names of the components of the calculating device were borrowed from the textile industry. In the textile industry, yarn was brought from the store to be milled. The device had a store which consisted of memory to hold 1,000 numbers of 50 decimal digits each. Numbers from the store were transferred to the mill for processing. The engine was programmed using two sets of perforated cards. One set directed
4046-618: The Busicom calculator. Five months after its release, Intel released the Intel 8008 , an 8-bit microprocessor. Bill Pentz led a team at Sacramento State to build the first microcomputer using the Intel 8008: the Sac State 8008 (1972). Its purpose was to store patient medical records. The computer supported a disk operating system to run a Memorex , 3- megabyte , hard disk drive . It had
4165-557: The Internet in its early years, and e-mail gateways between Internet SMTP -based mail and UUCP mail were developed. A user at a system with UUCP connections could thereby exchange mail with Internet users, and the Internet links could be used to bypass large portions of the slow UUCP network. A "UUCP zone" was defined within the Internet domain namespace to facilitate these interfaces. With this infrastructure in place, UUCP's strength
4284-495: The Usenet network, though not for routing; they are used to record, in the header of a message, the nodes through which that message has passed, rather than to direct where it will go next. "Bang path" is also used as an expression for any explicitly specified routing path between network hosts. That usage is not necessarily limited to UUCP, IP routing, email messaging, or Usenet. The concept of delay-tolerant networking protocols
4403-698: The VA3400 which performed full-duplex at 1,200 bit/s over a normal phone line. In November 1976, AT&T introduced the 212A modem, similar in design, but using the lower frequency set for transmission. It was not compatible with the VA3400, but it would operate with 103A modem at 300 bit/s. In 1977, Vadic responded with the VA3467 triple modem, an answer-only modem sold to computer center operators that supported Vadic's 1,200-bit/s mode, AT&T's 212A mode, and 103A operation. A significant advance in modems
4522-461: The " @ notation ", even by sites still using UUCP. A UUCP-only site can register a DNS domain name, and have the DNS server that handles that domain provide MX records that cause Internet mail to that site to be delivered to a UUCP host on the Internet that can then deliver the mail to the UUCP site. UUCPNET was the name for the totality of the network of computers connected through UUCP. This network
4641-455: The 1960s, controlling the electrical flow migrated to programming a matrix of read-only memory (ROM). The matrix resembled a two-dimensional array of fuses. The process to embed instructions onto the matrix was to burn out the unneeded connections. There were so many connections, firmware programmers wrote a computer program on another chip to oversee the burning. The technology became known as Programmable ROM . In 1971, Intel installed
4760-757: The 1970s, independently made modems compatible with the Bell 103 de facto standard were commonplace. Example models included the Novation CAT and the Anderson-Jacobson . A lower-cost option was the Pennywhistle modem , designed to be built using readily available parts. Teletype machines were granted access to remote networks such as the Teletypewriter Exchange using the Bell 103 modem. AT&T also produced reduced-cost units,
4879-625: The DNS; .uucp works where it needs to; some hosts punt mail out of SMTP queue into uucp queues on gateway machines if a .uucp address is recognized on an incoming SMTP connection. Usenet traffic was originally transmitted over the UUCP protocol using bang paths. These are still in use within Usenet message format Path header lines. They now have only an informational purpose, and are not used for routing, although they can be used to ensure that loops do not occur. In general, like other older e-mail address formats , bang paths have now been superseded by
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4998-592: The ENIAC project. On June 30, 1945, von Neumann published the First Draft of a Report on the EDVAC , which equated the structures of the computer with the structures of the human brain. The design became known as the von Neumann architecture . The architecture was simultaneously deployed in the constructions of the EDVAC and EDSAC computers in 1949. The IBM System/360 (1964) was a family of computers, each having
5117-600: The ENIAC took up to two months. Three function tables were on wheels and needed to be rolled to fixed function panels. Function tables were connected to function panels by plugging heavy black cables into plugboards . Each function table had 728 rotating knobs. Programming the ENIAC also involved setting some of the 3,000 switches. Debugging a program took a week. It ran from 1947 until 1955 at Aberdeen Proving Ground , calculating hydrogen bomb parameters, predicting weather patterns, and producing firing tables to aim artillery guns. Instead of plugging in cords and turning switches,
5236-576: The SAGE director centers scattered around the United States and Canada . Shortly afterwards in 1959, the technology in the SAGE modems was made available commercially as the Bell 101 , which provided 110 bit/s speeds. Bell called this and several other early modems "datasets". Some early modems were based on touch-tone frequencies, such as Bell 400-style touch-tone modems. The Bell 103A standard
5355-521: The Smartmodem made communications much simpler and more easily accessed. This provided a growing market for other vendors, who licensed the Hayes patents and competed on price or by adding features. This eventually led to legal action over use of the patented Hayes command language. Dial modems generally remained at 300 and 1,200 bit/s (eventually becoming standards such as V.21 and V.22 ) into
5474-404: The UUCP stack. The packet format consisted of a 6-byte header and then between zero and 4096 bytes in the payload. The packet starts with a single \020 (control-P). This is followed by a single byte, known as "K", containing a value of 1 to 8 indicating a packet size from 32 to 4096 bytes, or a 9 indicating a control packet. Many systems only supported K=2, meaning 64 bytes. The next two bytes were
5593-405: The adjacent machine name, an exclamation mark (often pronounced bang ), followed by the user name on the adjacent machine. For example, the address barbox!user would refer to user user on adjacent machine barbox . Mail could furthermore be routed through the network, traversing any number of intermediate nodes before arriving at its destination. Initially, this had to be done by specifying
5712-432: The caller's machine and begin a session. The session has three distinct stages: On starting, uucico will respond by sending an identification string, \20Shere= hostname \0 , where \20 is the control-P character, and \0 is a trailing null. The caller's UUCP responds with \20S callername options \0 , where options is a string containing zero or more Unix-like option switches. These can include packet and window sizes,
5831-404: The complete path, with a list of intermediate host names separated by bangs. For example, if machine barbox is not connected to the local machine, but it is known that barbox is connected to machine foovax which does communicate with the local machine, the appropriate address to send mail to would be foovax!barbox!user . User barbox!user would generally publish their UUCP email address in
5950-483: The computer program onto the chip and named it the Intel 4004 microprocessor . The terms microprocessor and central processing unit (CPU) are now used interchangeably. However, CPUs predate microprocessors. For example, the IBM System/360 (1964) had a CPU made from circuit boards containing discrete components on ceramic substrates . The Intel 4004 (1971) was a 4- bit microprocessor designed to run
6069-465: The computer. They follow a set of rules called a syntax . Programming languages get their basis from formal languages . The purpose of defining a solution in terms of its formal language is to generate an algorithm to solve the underlining problem. An algorithm is a sequence of simple instructions that solve a problem. The evolution of programming languages began when the EDSAC (1949) used
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#17327723681076188-642: The computers' modems to dial out to other computers, establishing temporary, point-to-point links between them. Each system in a UUCP network has a list of neighbor systems, with phone numbers, login names and passwords, etc. When work (file transfer or command execution requests) is queued for a neighbor system, the uucico program typically calls that system to process the work. The uucico program can also poll its neighbors periodically to check for work queued on their side; this permits neighbors without dial-out capability to participate. Over time, dial-up links were replaced by Internet connections, and UUCP added
6307-510: The connection between devices was normally manual, using an attached telephone handset . By the 1970s, higher speeds of 1,200 and 2,400 bit/s for asynchronous dial connections, 4,800 bit/s for synchronous leased line connections and 35 kbit/s for synchronous conditioned leased lines were available. By the 1980s, less expensive 1,200 and 2,400 bit/s dialup modems were being released, and modems working on radio and other systems were available. As device sophistication grew rapidly in
6426-522: The definition of a modem may have been the multiplexers used by news wire services in the 1920s. In 1941, the Allies developed a voice encryption system called SIGSALY which used a vocoder to digitize speech, then encrypted the speech with one-time pad and encoded the digital data as tones using frequency shift keying. This was also a digital modulation technique, making this an early modem. Commercial modems largely did not become available until
6545-434: The descendants include C , C++ and Java . BASIC (1964) stands for "Beginner's All-Purpose Symbolic Instruction Code". It was developed at Dartmouth College for all of their students to learn. If a student did not go on to a more powerful language, the student would still remember Basic. A Basic interpreter was installed in the microcomputers manufactured in the late 1970s. As the microcomputer industry grew, so did
6664-417: The digitization itself placed constraints on the types of waveforms that could be reliably encoded. The first problem was that the process of analog-to-digital conversion is intrinsically lossy, but second, and more importantly, the digital signals used by the telcos were not "linear": they did not encode all frequencies the same way, instead utilizing a nonlinear encoding ( μ-law and a-law ) meant to favor
6783-491: The entire file is sent as a single long string followed by a whole-file checksum. The similar x-protocol appears to have seen little or no use. d-protocol was similar to x, but intended for use on Datakit networks that connected many of Bell Labs offices. t-protocol originated in the BSD versions of UUCP and like some similar ones, is designed to run over 8-bit error-free TCP/IP links. It has no error correction at all, and
6902-647: The first stored computer program in its von Neumann architecture . Programming the EDSAC was in the first generation of programming language . Imperative languages specify a sequential algorithm using declarations , expressions , and statements : FORTRAN (1958) was unveiled as "The IBM Mathematical FORmula TRANslating system". It was designed for scientific calculations, without string handling facilities. Along with declarations , expressions , and statements , it supported: It succeeded because: However, non-IBM vendors also wrote Fortran compilers, but with
7021-432: The full spectrum of the phone line, improving the available bandwidth. Additional improvements were introduced by quadrature amplitude modulation (QAM) encoding, which increased the number of bits per symbol to four through a combination of phase shift and amplitude. Transmitting at 1,200 baud produced the 4,800 bit/s V.27ter standard, and at 2,400 baud the 9,600 bit/s V.32 . The carrier frequency
7140-539: The halt state. All present-day computers are Turing complete . The Electronic Numerical Integrator And Computer (ENIAC) was built between July 1943 and Fall 1945. It was a Turing complete , general-purpose computer that used 17,468 vacuum tubes to create the circuits . At its core, it was a series of Pascalines wired together. Its 40 units weighed 30 tons, occupied 1,800 square feet (167 m ), and consumed $ 650 per hour ( in 1940s currency ) in electricity when idle. It had 20 base-10 accumulators . Programming
7259-479: The language BCPL was replaced with B , and AT&T Bell Labs called the next version "C". Its purpose was to write the UNIX operating system . C is a relatively small language, making it easy to write compilers. Its growth mirrored the hardware growth in the 1980s. Its growth also was because it has the facilities of assembly language , but uses a high-level syntax . It added advanced features like: C allows
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#17327723681077378-400: The language. Basic pioneered the interactive session . It offered operating system commands within its environment: However, the Basic syntax was too simple for large programs. Recent dialects added structure and object-oriented extensions. Microsoft's Visual Basic is still widely used and produces a graphical user interface . C programming language (1973) got its name because
7497-410: The language. If the executable is requested for execution, then the operating system loads it into memory and starts a process . The central processing unit will soon switch to this process so it can fetch, decode, and then execute each machine instruction. If the source code is requested for execution, then the operating system loads the corresponding interpreter into memory and starts
7616-710: The late 1950s, when the rapid development of computer technology created demand for a method of connecting computers together over long distances, resulting in the Bell Company and then other businesses producing an increasing number of computer modems for use over both switched and leased telephone lines. Later developments would produce modems that operated over cable television lines , power lines , and various radio technologies , as well as modems that achieved much higher speeds over telephone lines. A dial-up modem transmits computer data over an ordinary switched telephone line that has not been designed for data use. It
7735-601: The late 1980s, many modems could support improved standards like this, and 2,400-bit/s operation was becoming common. Increasing modem speed greatly improved the responsiveness of online systems and made file transfer practical. This led to rapid growth of online services with large file libraries, which in turn gave more reason to own a modem. The rapid update of modems led to a similar rapid increase in BBS use. The introduction of microcomputer systems with internal expansion slots made small internal modems practical. This led to
7854-418: The late 1990s and the emergence of smartphones in the 2000s led to the development of ever-faster radio-based systems. Today, modems are ubiquitous and largely invisible, included in almost every mobile computing device in one form or another, and generally capable of speeds on the order of tens or hundreds of megabytes per second. Modems are frequently classified by the maximum amount of data they can send in
7973-431: The late 1990s, telephone-based modems quickly exhausted the available bandwidth , reaching 56 kbit/s. The rise of public use of the internet during the late 1990s led to demands for much higher performance, leading to the move away from audio-based systems to entirely new encodings on cable television lines and short-range signals in subcarriers on telephone lines. The move to cellular telephones , especially in
8092-466: The lengthy introduction of the 28,800 bit/s V.34 standard. While waiting, several companies decided to release hardware and introduced modems they referred to as V.Fast . In order to guarantee compatibility with V.34 modems once a standard was ratified (1994), manufacturers used more flexible components, generally a DSP and microcontroller , as opposed to purpose-designed ASIC modem chips. This would allow later firmware updates to conform with
8211-465: The local system). Some versions of the suite include uuencode / uudecode (convert 8-bit binary files to 7-bit text format and vice versa). Although UUCP was originally developed on Unix in the 1970s and 1980s, and is most closely associated with Unix-like systems, UUCP implementations exist for several non-Unix-like operating systems, including DOS , OS/2 , OpenVMS (for VAX hardware only), AmigaOS , classic Mac OS , and even CP/M . UUCP
8330-769: The market around February 1997; although problems with K56Flex modems were noted in product reviews through July, within six months the two technologies worked equally well, with variations dependent largely on local connection characteristics. The retail price of these early 56k modems was about US$ 200 , compared to $ 100 for standard 33k modems. Compatible equipment was also required at the Internet service providers (ISPs) end, with costs varying depending on whether their current equipment could be upgraded. About half of all ISPs offered 56k support by October 1997. Consumer sales were relatively low, which USRobotics and Rockwell attributed to conflicting standards. In February 1998, The International Telecommunication Union (ITU) announced
8449-518: The market when V.32bis was standardized, which operated at 14,400 bit/s. Rockwell International 's chip division developed a new driver chip set incorporating the V.32bis standard and aggressively priced it. Supra, Inc. arranged a short-term exclusivity arrangement with Rockwell, and developed the SupraFAXModem 14400 based on it. Introduced in January 1992 at $ 399 (or less), it was half
8568-480: The maximum supported file size, debugging options, and others. Depending on the setup of the two systems, the call may end here. For instance, when the caller responds with their system name, the called system may optionally hang up if it does not recognize the caller, sending the RYou are unknown to me\0 response string and then disconnecting. If the two systems successfully handshake, the caller will now begin to send
8687-469: The mid-1980s. Commodore's 1982 VicModem for the VIC-20 was the first modem to be sold under $ 100, and the first modem to sell a million units. In 1984, V.22bis was created, a 2,400-bit/s system similar in concept to the 1,200-bit/s Bell 212. This bit rate increase was achieved by defining four or sixteen distinct symbols, which allowed the encoding of two or four bits per symbol instead of only one. By
8806-602: The modem sends a new signal. For example, the ITU-T V.21 standard used audio frequency-shift keying with two possible frequencies, corresponding to two distinct symbols (or one bit per symbol), to carry 300 bits per second using 300 baud. By contrast, the original ITU-T V.22 standard, which could transmit and receive four distinct symbols (two bits per symbol), transmitted 1,200 bits by sending 600 symbols per second (600 baud) using phase-shift keying . Many modems are variable-rate, permitting them to be used over
8925-440: The network beyond the interconnected university systems. FSUUCP formed the basis for many bulletin board system (BBS) packages such as Galacticomm's Major BBS and Mustang Software 's Wildcat! BBS to connect to the UUCP network and exchange email and Usenet traffic. As an example, UFGATE (John Galvin, Garry Paxinos, Tim Pozar) was a package that provided a gateway between networks running Fidonet and UUCP protocols. FSUUCP
9044-400: The nonlinear response of the human ear to voice signals. This made it very difficult to find a 56 kbit/s encoding that could survive the digitizing process. Modem manufacturers discovered that, while the analog to digital conversion could not preserve higher speeds, digital-to-analog conversions could. Because it was possible for an ISP to obtain a direct digital connection to a telco,
9163-472: The number of packets in a window, then sending another packet with XXX=6 and YYY as the packet length (encoded as it would be in K) and then a third packet that is identical to the first but XXX=5. g-protocol uses a simple sliding window system to deal with potentially long latencies between endpoints. The protocol allows packets to size from 64 to 4096 8-bit bytes, and windows that include 1 to 7 packets. In theory,
9282-486: The operation and the other set inputted the variables. However, the thousands of cogged wheels and gears never fully worked together. Ada Lovelace worked for Charles Babbage to create a description of the Analytical Engine (1843). The description contained Note G which completely detailed a method for calculating Bernoulli numbers using the Analytical Engine. This note is recognized by some historians as
9401-428: The originate-only 113D and the answer-only 113B/C modems. The 201A Data-Phone was a synchronous modem using two-bit-per-symbol phase-shift keying (PSK) encoding, achieving 2,000 bit/s half-duplex over normal phone lines. In this system the two tones for any one side of the connection are sent at similar frequencies as in the 300 bit/s systems, but slightly out of phase. In early 1973, Vadic introduced
9520-582: The path pdp10!router22!bigsite!foovax!barbox!user ). Many users would suggest multiple routes from various large well-known sites, providing even better and perhaps faster connection service from the mail sender. An email address of this form was known as a bang path . Bang paths of eight to ten machines (or hops ) were not uncommon in 1981, and late-night dial-up UUCP links could cause week-long transmission times. Bang paths were often selected by both transmission time and reliability, as messages would often get lost. Some hosts went so far as to try to " rewrite "
9639-427: The path, sending mail via "faster" routes—this practice tended to be frowned upon. The "pseudo-domain" ending .uucp was sometimes used to designate a hostname as being reachable by UUCP networking, although this was never formally registered in the domain name system (DNS) as a top-level domain . The uucp community administered itself and did not mesh well with the administration methods and regulations governing
9758-402: The performance of g-protocol transfers by noticing end-of-packet markers being sent to the remote system and immediately sending an ACK back to the local host, pretending that the remote system had already received the packet and decoded it correctly. This triggered the software stack to send the next packet, so rapidly that the transfer became almost continuous. The data between the two modems
9877-564: The price of the slower V.32 modems already on the market. This led to a price war, and by the end of the year V.32 was dead, never having been really established, and V.32bis modems were widely available for $ 250 . V.32bis was so successful that the older high-speed standards had little advantages. USRobotics (USR) fought back with a 16,800 bit/s version of HST, while AT&T introduced a one-off 19,200 bit/s method they referred to as V.32ter , but neither non-standard modem sold well. Consumer interest in these proprietary improvements waned during
9996-443: The programmer to control which region of memory data is to be stored. Global variables and static variables require the fewest clock cycles to store. The stack is automatically used for the standard variable declarations . Heap memory is returned to a pointer variable from the malloc() function. In the 1970s, software engineers needed language support to break large projects down into modules . One obvious feature
10115-399: The programs in the suite; it provides a user interface for requesting file copy operations. The UUCP suite also includes uux (user interface for remote command execution), uucico (the communication program that performs the file transfers), uustat (reports statistics on recent activity), uuxqt (execute commands sent from remote machines), and uuname (reports the UUCP name of
10234-501: The project contributed to the development of the Intel 8080 (1974) instruction set . In 1978, the modern software development environment began when Intel upgraded the Intel 8080 to the Intel 8086 . Intel simplified the Intel 8086 to manufacture the cheaper Intel 8088 . IBM embraced the Intel 8088 when they entered the personal computer market (1981). As consumer demand for personal computers increased, so did Intel's microprocessor development. The succession of development
10353-414: The protocol consists simply of breaking up command and file data into 512 or 1024-byte packets to easily fit within typical TCP frames. e-protocol ("e" for Ethernet) was developed by Clem Cole at MASSCOMP and was widely released by Brian Redman in the later HoneyDanBer versions. It was developed and released before the t-protocol, but the t-protocol was more commonly used because the BSD version of UUCP
10472-476: The receiver demodulates the signal to recreate the original digital information. The goal is to produce a signal that can be transmitted easily and decoded reliably. Modems can be used with almost any means of transmitting analog signals, from LEDs to radio . Early modems were devices that used audible sounds suitable for transmission over traditional telephone systems and leased lines . These generally operated at 110 or 300 bits per second (bit/s), and
10591-510: The remote system whenever a next-hop node is available. The remote system will then execute the requested command and return the result, when the original system is available. Both of these transfers may be indirect, via multi-hop paths, with arbitrary windows of availability. Even when executing a command on an always-available neighbor, uux is not instant. UUCP usage began to die out with the rise of Internet service providers offering inexpensive SLIP and PPP services. The UUCP Mapping Project
10710-446: The same instruction set architecture . The Model 20 was the smallest and least expensive. Customers could upgrade and retain the same application software . The Model 195 was the most premium. Each System/360 model featured multiprogramming —having multiple processes in memory at once. When one process was waiting for input/output , another could compute. IBM planned for each model to be programmed using PL/1 . A committee
10829-438: The set of students is a subset of the set of persons. As a result, students inherit all the attributes common to all persons. Additionally, students have unique attributes that other people do not have. Object-oriented languages model subset/superset relationships using inheritance . Object-oriented programming became the dominant language paradigm by the late 1990s. C++ (1985) was originally called "C with Classes". It
10948-435: The speed of a 2400 bit/s modem. They were widely used on UUCP hosts as they could quickly pay for themselves in reduced long-distance charges. UUCP implementations also include other transfer protocols for use over certain links. f-protocol is designed to run over 7-bit error-corrected links. This was originally intended for use on X.25 links, which were popular for a time in the 1980s. It does not packetize data, instead,
11067-467: The standards once ratified. The ITU standard V.34 represents the culmination of these joint efforts. It employed the most powerful coding techniques available at the time, including channel encoding and shape encoding. From the mere four bits per symbol ( 9.6 kbit/s ), the new standards used the functional equivalent of 6 to 10 bits per symbol, plus increasing baud rates from 2,400 to 3,429, to create 14.4, 28.8, and 33.6 kbit/s modems. This rate
11186-423: The time technology companies began to investigate speeds above 33.6 kbit/s , telephone companies had switched almost entirely to all-digital networks. As soon as a phone line reached a local central office, a line card converted the analog signal from the subscriber to a digital one and conversely. While digitally encoded telephone lines notionally provide the same bandwidth as the analog systems they replaced,
11305-497: The underlying g-protocol is responsible for transferring information in an error-free form. The protocol originated as a general-purpose system for packet delivery, and thus offers a number of features that are not used by the UUCP package as a whole. These include a secondary channel that can send command data interspersed with a file transfer, and the ability to renegotiate the packet and window sizes during transmission. These extra features may not be available in some implementations of
11424-507: The world's first computer program . In 1936, Alan Turing introduced the Universal Turing machine , a theoretical device that can model every computation. It is a finite-state machine that has an infinitely long read/write tape. The machine can move the tape back and forth, changing its contents as it performs an algorithm . The machine starts in the initial state, goes through a sequence of steps, and halts when it encounters
11543-435: Was rewritten by AT&T researchers Peter Honeyman, David A. Nowitz, and Brian E. Redman around 1983. The rewrite is referred to as HDB or HoneyDanBer uucp, which was later enhanced, bug fixed, and repackaged as BNU UUCP ("Basic Network Utilities"). Each of these versions was distributed as proprietary software, which inspired Ian Lance Taylor to write a new free software version from scratch in 1991. Taylor UUCP
11662-499: Was 1,650 Hz in both systems. The introduction of these higher-speed systems also led to the development of the digital fax machine during the 1980s. While early fax technology also used modulated signals on a phone line, digital fax used the now-standard digital encoding used by computer modems. This eventually allowed computers to send and receive fax images. In the early 1990s, V.32 modems operating at 9,600 bit/s were introduced, but were expensive and were only starting to enter
11781-469: Was a proprietary design from USRobotics , which they called "X2" because 56k was twice the speed (×2) of 28k modems. At that time, USRobotics held a 40% share of the retail modem market, while Rockwell International held an 80% share of the modem chipset market. Concerned with being shut out, Rockwell began work on a rival 56k technology. They joined with Lucent and Motorola to develop what they called "K56Flex" or just "Flex". Both technologies reached
11900-400: Was a volunteer, largely successful effort to build a map of the connections between machines that were open mail relays and establish a managed namespace. Each system administrator would submit, by e-mail, a list of the systems to which theirs would connect, along with a ranking for each such connection. These submitted map entries were processed by an automatic program that combined them into
12019-575: Was contributed to UUCP Debian Linux package to adapt for the HERMES (High-Frequency Emergency and Rural Multimedia Exchange System) project, which provides UUCP HF connectivity. In the mid 2000s, UUCP over TCP/IP (often encrypted, using the SSH protocol) was proposed for use when a computer does not have any fixed IP addresses but is still willing to run a standard mail transfer agent (MTA) like Sendmail or Postfix . Bang-like paths are still in use within
12138-427: Was designed to expand C's capabilities by adding the object-oriented facilities of the language Simula . An object-oriented module is composed of two files. The definitions file is called the header file . Here is a C++ header file for the GRADE class in a simple school application: A constructor operation is a function with the same name as the class name. It is executed when the calling operation executes
12257-440: Was error-corrected using a proprietary protocol based on MNP that ran over Telebit's half-duplex connections much better than g-protocol would normally, because in the common 64x3 case the remote system would be sending a constant stream of ACK s that would overflow the low-speed return channel. Combined with the modem's naturally higher data rates, they greatly improved overall throughput and generally performed about seven times
12376-550: Was formally shut down in late 2000. The UUCP protocol has now mostly been replaced by the Internet TCP/IP based protocols SMTP for mail and NNTP for Usenet news. In July 2012, Dutch Internet provider XS4ALL closed down its UUCP service, claiming it was "probably one of the last providers in the world that still offered it"; it had only 13 users at that time (prior to its shut-down it had refused requests from new users for several years). One surviving feature of UUCP
12495-437: Was formed that included COBOL , Fortran and ALGOL programmers. The purpose was to develop a language that was comprehensive, easy to use, extendible, and would replace Cobol and Fortran. The result was a large and complex language that took a long time to compile . Computers manufactured until the 1970s had front-panel switches for manual programming. The computer program was written on paper for reference. An instruction
12614-458: Was integrated into devices from many other manufacturers. Automatic dialing was not a new capability—it had been available via separate Automatic Calling Units , and via modems using the X.21 interface —but the Smartmodem made it available in a single device that could be used with even the most minimal implementations of the ubiquitous RS-232 interface, making this capability accessible from virtually any system or language. The introduction of
12733-412: Was introduced by AT&T in 1962. It provided full-duplex service at 300 bit/s over normal phone lines. Frequency-shift keying was used, with the call originator transmitting at 1,070 or 1,270 Hz and the answering modem transmitting at 2,025 or 2,225 Hz. The 103 modem would eventually become a de facto standard once third-party (non-AT&T modems) reached the market, and throughout
12852-548: Was once a widely known technology, mass-marketed globally dial-up internet access . In the 1990s, tens of millions of people in the United States alone used dial-up modems for internet access. Dial-up service has since been largely superseded by broadband internet , such as DSL . Mass production of telephone line modems in the United States began as part of the SAGE air-defense system in 1958, connecting terminals at various airbases, radar sites, and command-and-control centers to
12971-614: Was originally written at AT&T Bell Laboratories by Mike Lesk . By 1978 it was in use on 82 UNIX machines inside the Bell system, primarily for software distribution. It was released in 1979 as part of Version 7 Unix . The first UUCP emails from the U.S. arrived in the United Kingdom in 1979 and email between the UK, the Netherlands and Denmark started in 1980, becoming a regular service via EUnet in 1982. The original UUCP
13090-799: Was released under the GNU General Public License . Taylor UUCP addressed security holes which allowed some of the original network worms to remotely execute unexpected shell commands. Taylor UUCP also incorporated features of all previous versions of UUCP, allowing it to communicate with any other version and even use similar config file formats from other versions. UUCP was also implemented for non- UNIX operating systems, most-notably DOS systems. Packages such as UUSLAVE/GNUUCP ( John Gilmore , Garry Paxinos, Tim Pozar), UUPC/extended (Drew Derbyshire of Kendra Electronic Wonderworks) and FSUUCP (Christopher Ambler of IODesign), brought early Internet connectivity to personal computers, expanding
13209-408: Was represented by a configuration of on/off settings. After setting the configuration, an execute button was pressed. This process was then repeated. Computer programs also were automatically inputted via paper tape , punched cards or magnetic-tape . After the medium was loaded, the starting address was set via switches, and the execute button was pressed. A major milestone in software development
13328-457: Was revisited in the early 2000s. Similar techniques as those used by UUCP can apply to other networks that experience delay or significant disruption. Computer program A computer program is a sequence or set of instructions in a programming language for a computer to execute . It is one component of software , which also includes documentation and other intangible components. A computer program in its human-readable form
13447-407: Was that it permitted a site to gain Internet e-mail and Usenet connectivity with only a dial-up modem link to another cooperating computer. This was at a time when true Internet access required a leased data line providing a connection to an Internet Point of Presence , both of which were expensive and difficult to arrange. By contrast, a link to the UUCP network could usually be established with
13566-536: Was the Hayes Smartmodem , introduced in 1981. The Smartmodem was an otherwise standard 103A 300 bit/s direct-connect modem, but it introduced a command language which allowed the computer to make control requests, such as commands to dial or answer calls, over the same RS-232 interface used for the data connection. The command set used by this device became a de facto standard, the Hayes command set , which
13685-402: Was the dominant implementation. The e-protocol differs from the t-protocol only in that commands are not packetized and are instead sent as normal strings, while files are padded to the nearest 20 bytes. The uucp and uuxqt capabilities could be used to send email between machines, with suitable mail user interfaces and delivery agent programs. A simple UUCP mail address was formed from
13804-543: Was the invention of the Very Large Scale Integration (VLSI) circuit (1964). Following World War II , tube-based technology was replaced with point-contact transistors (1947) and bipolar junction transistors (late 1950s) mounted on a circuit board . During the 1960s , the aerospace industry replaced the circuit board with an integrated circuit chip . Robert Noyce , co-founder of Fairchild Semiconductor (1957) and Intel (1968), achieved
13923-466: Was the only other implementation of Taylor's enhanced 'i' protocol, a significant improvement over the standard 'g' protocol used by most UUCP implementations. Before the widespread availability of Internet access , computers were only connected by smaller local area networks within a company or organization. They were also often equipped with modems so they could be used remotely from character-mode terminals via dial-up telephone lines . UUCP used
14042-405: Was to decompose large projects physically into separate files . A less obvious feature was to decompose large projects logically into abstract data types . At the time, languages supported concrete (scalar) datatypes like integer numbers, floating-point numbers, and strings of characters . Abstract datatypes are structures of concrete datatypes, with a new name assigned. For example,
14161-422: Was very informal, maintained in a spirit of mutual cooperation between systems owned by thousands of private companies, universities, and so on. Often, particularly in the private sector, UUCP links were established without official approval from the companies' upper management. The UUCP network was constantly changing as new systems and dial-up links were added, others were removed, etc. The UUCP Mapping Project
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