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XModem
XMODEM is a simple file transfer protocol developed as a quick hack by Ward Christensen for use in his 1977 MODEM.ASM terminal program. It allowed users to transmit files between their computers when both sides used MODEM. Keith Petersen made a minor update to always turn on "quiet mode", and called the result XMODEM. XMODEM, like most file transfer protocols, breaks up the original data into a series of " packets" that are sent to the receiver, along with additional information allowing the receiver to determine whether that packet was correctly received. If an error is detected, the receiver requests that the packet be re-sent. A string of bad packets causes the transfer to abort. XMODEM became extremely popular in the early bulletin board system (BBS) market, largely because it was simple to implement. It was also fairly inefficient, and as modem speeds increased, this problem led to the development of a number of modified versions of XMODEM to improve performance or address ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ward Christensen
Ward Leon Christensen (October 23, 1945 – October 11, 2024) was an American computer scientist who was the inventor of the XMODEM file transfer protocol and a co-founder of the CBBS bulletin board, the first bulletin board system (BBS) ever brought online. Early life Christensen was born on October 23, 1945, in West Bend, Wisconsin, to Florence (née Hohmann) and Roy Christensen. His father was a safety director at West Bend Company and his mother sold '' World Book'' encyclopedias. Christensen also had a brother, Donald Christensen. Christensen attended West Bend High School. In his senior year of high school in 1963, he created a computer that won first place in a science fair. After graduating high school, Christensen attended the University of Wisconsin–Madison before transferring to Milton College. He graduated from Milton College with a Bachelor of Arts degree in physics and chemistry in 1968. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Channel Efficiency
Network throughput (or just throughput, when in context) refers to the rate of message delivery over a communication channel in a communication network, such as Ethernet or packet radio. The data that these messages contain may be delivered over physical or logical links, or through network nodes. Throughput is usually measured in bits per second (, sometimes abbreviated bps), and sometimes in packets per second ( or pps) or data packets per time slot. The system throughput or aggregate throughput is the sum of the data rates that are delivered over all channels in a network. Throughput represents digital bandwidth consumption. The throughput of a communication system may be affected by various factors, including the limitations of the underlying physical medium, available processing power of the system components, end-user behavior, etc. When taking various protocol overheads into account, the useful rate of the data transfer can be significantly lower than the maximum achie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclic Redundancy Check
A cyclic redundancy check (CRC) is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to digital data. Blocks of data entering these systems get a short ''check value'' attached, based on the remainder of a polynomial division of their contents. On retrieval, the calculation is repeated and, in the event the check values do not match, corrective action can be taken against data corruption. CRCs can be used for error correction (see bitfilters). CRCs are so called because the ''check'' (data verification) value is a ''redundancy'' (it expands the message without adding information) and the algorithm is based on ''cyclic'' codes. CRCs are popular because they are simple to implement in binary hardware, easy to analyze mathematically, and particularly good at detecting common errors caused by noise in transmission channels. Because the check value has a fixed length, the function that generates it is occasionally used as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SEAlink
Sealink was a ferry company based in Great Britain from 1970 to 1984, operating services to France, Belgium, the Netherlands, the Isle of Man, the Channel Islands, the Isle of Wight and Ireland. Ports served by the company included: Dover, Folkestone, Newhaven, Southampton and Harwich for services to the European continent; Holyhead, Fishguard, Heysham and Stranraer for services to Ireland and the Isle of Man; Weymouth and Portsmouth for services to the Channel Islands. The Isle of Wight was also served from Portsmouth and Lymington. Sealink also operated the ''Steamer'' passenger ferry services on Windermere in Cumbria until privatisation, when these were passed to the newly reformed Windermere Iron Steamboat Company (now Windermere Lake Cruises Ltd). History Sealink was originally the brand name for the ferry services of British Rail in the United Kingdom and Ireland. Services to France, Belgium and the Netherlands were run by Sealink UK as part of the Sealink consort ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Timestamp
A timestamp is a sequence of characters or encoded information identifying when a certain event occurred, usually giving date and time of day, sometimes accurate to a small fraction of a second. Timestamps do not have to be based on some absolute notion of time, however. They can have any epoch, can be relative to any arbitrary time, such as the power-on time of a system, or to some arbitrary time in the past. A distinction is sometimes made between the terms datestamp, timestamp and date-timestamp: * Datestamp or DS: A date, for example -- according to ISO 8601 * Timestamp or TS: A time of day, for example :: using 24-hour clock * Date-timestamp or DTS: Date and time, for example --, :: History The term "timestamp" derives from rubber stamps used in offices to stamp the current date, and sometimes time, in ink on paper documents, to record when the document was received. Common examples of this type of timestamp are a postmark on a letter or the "in" and "out" times on a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FidoNet
__ / \ /, oo \ (_, /_) _`@/_ \ _ , , \ \\ , (*) , \ )) ______ , __U__, / \// / FIDO \ _//, , _\ / (________) (_/(_, (____/ (c) John Madill FidoNet logo by John Madill FidoNet is a worldwide computer network that is used for communication between bulletin board systems (BBSes). It uses a store-and-forward system to exchange private (email) and public (forum) messages between the BBSes in the network, as well as other files and protocols in some cases. The FidoNet system was based on several small interacting programs, only one of which needed to be Porting, ported to support other BBS software. FidoNet was one of the few networks that was supported by almost all BBS software, as well as a number of non-BBS online services. This modular construction also allowed FidoNet to easily upgrade to new data c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tom Jennings
Thomas Daniel Jennings (born 1955) is a Los Angeles-based artist and computer programmer, known for his work that led to FidoNet (the first message and file networking bulletin board system, or BBS), and for his work at Phoenix Software on MS-DOS integration and interoperability. Work In 1983, Jennings created the Fido program, which spawned FidoNet, the first message and file networking bulletin board system (BBS). The FidoNet protocols were authored by Jennings in the Fido program, and they were ultimately implemented by numerous authors in other software to create the full BBS, network using a multiplicity of platforms. Aside from creating the protocol for networking BBSes, Jennings: built '' Wired''s first internet presence; wrote the portable BIOS that led to Phoenix Technologies BIOS, contributing to on MS-DOS integration and interoperability; ran an early regional internet service providerThe Little Garden (later incorporated as TLGnet, Inc); and maintains an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jerry Pournelle
Jerry Eugene Pournelle (; August 7, 1933 – September 8, 2017) was an American scientist in the area of operations research and ergonomics, human factors research, a science fiction writer, essayist, journalist, and one of the first bloggers. In the 1960s and early 1970s, he worked in the aerospace industry, but eventually focused on his writing career. In an obituary in ''Gizmodo'', he was described as "a tireless ambassador for the future." Pournelle's hard science fiction writing received multiple awards. In addition to his solo writing, he wrote several novels with collaborators including Larry Niven. Pournelle served a term as President of the Science Fiction and Fantasy Writers of America. Pournelle's journalism focused primarily on the computer industry, astronomy, and space exploration. From the 1970s until the early 1990s, he contributed to the computer magazine ''Byte (magazine), Byte'', writing from the viewpoint of an intelligent user, with the oft-cited credo, "We ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MS-DOS
MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few operating systems attempting to be compatible with MS-DOS, are sometimes referred to as "DOS" (which is also the generic acronym for disk operating system). MS-DOS was the main operating system for IBM PC compatibles during the 1980s, from which point it was gradually superseded by operating systems offering a graphical user interface (GUI), in various generations of the graphical Microsoft Windows operating system. IBM licensed and re-released it in 1981 as PC DOS 1.0 for use in its PCs. Although MS-DOS and PC DOS were initially developed in parallel by Microsoft and IBM, the two products diverged after twelve years, in 1993, with recognizable differences in compatibility, syntax and capabilities. Beginning in 1988 with DR-DOS, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating System
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for efficient use of the system and may also include accounting software for cost allocation of Scheduling (computing), processor time, mass storage, peripherals, and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computerfrom cellular phones and video game consoles to web servers and supercomputers. , Android (operating system), Android is the most popular operating system with a 46% market share, followed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acoustic Coupler
In telecommunications, an acoustic coupler is an interface device for coupling electrical signals by acoustical means—usually into and out of a telephone. The link is achieved through converting electric signals from the phone line to sound and reconverting sound to electric signals needed for the end terminal, such as a teletypewriter, and back, rather than through direct electrical connection. History and applications Prior to its breakup in 1984, Bell System's legal monopoly over telephony in the United States allowed the company to impose strict rules on how consumers could access their network. Customers were prohibited from connecting equipment not made or sold by Bell to the network. The same set-up was operative in nearly all countries, where the telephone companies were nationally owned. In many households, telephones were hard-wired to wall terminals before connectors like RJ11 and BS 6312 became standardized. The situation was similar in other countries. I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osborne 1
The Osborne 1 is the first commercially successful portable computer, released on April 3, 1981 by Osborne Computer Corporation. It weighs , cost US$1,795, and runs the CP/M 2.2 operating system. It is powered from a wall socket, as it has no on-board battery, but it is still classed as a portable device since it can be hand-carried when the keyboard is closed. The computer shipped with a large bundle of software that was almost equivalent in value to the machine itself, a practice adopted by other CP/M computer vendors. Competitors quickly appeared, such as the Kaypro II. History The Osborne 1 was developed by Adam Osborne and designed by Lee Felsenstein, first announced in early 1981. Osborne, an author of computer books decided that he wanted to break the price of computers. The computer's design was based largely on the Xerox NoteTaker, a prototype developed at Xerox PARC in 1976 by Alan Kay. It was designed to be portable, with a rugged ABS plastic case and a handle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
