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Pacific Cyber Metrix
Pacific Cyber/Metrix, Inc. (PC/M; originally PCM, Inc., later PCM Systems) was an American computer company based in California. The company was founded in 1975 in San Ramon, California. A privately held company, PC/M was founded by Robert Nelson and several others, most of whom including Nelson came from the San Ramon facility of Edgerton, Germeshausen, and Grier, a scientific research firm. Nelson was named president and general owner. For the next several years the company developed microcomputers based around the PDP-8–compatible Intersil 6100 as well as CMOS EPROM burners. The company earned profit from the cash flow generated by their products and received no outside venture capital. PC/M moved its headquarters in late 1979 to Dublin, California, where the company spent the remainder of its existence in a 6,000-square-foot facility. The company's workforce was relatively spartan throughout its lifespan, employing only "about 10" in 1979, later increasing to 15 by the ear ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
San Ramon, California
San Ramon ( Spanish: ''San Ramón'', meaning "St. Raymond") is a city in Contra Costa County, California, United States, located within the San Ramon Valley, and east of San Francisco. San Ramon's population was 84,605 per the 2020 census, making it the 4th largest city in Contra Costa County, behind Richmond, Concord and Antioch. San Ramon is home to the headquarters of Chevron Corporation, Cooper Companies, 24 Hour Fitness, the West Coast headquarters of AT&T, GE Digital, as well as the San Ramon Medical Center. Major annual events include the Art and Wind Festival on Memorial Day weekend and the Run for Education in October. On April 24, 2001, San Ramon was designated a Tree City USA. History The lands now occupied by the City of San Ramon were formerly inhabited by Seunen people, an Ohlone/Costanoan group who built their homes near creeks. Sometime around 1797, they were taken by Mission San José for use as grazing land. In 1834, they were part of the Ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bus (computing)
In computer architecture, a bus (shortened form of the Latin ''omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This expression covers all related hardware components (wire, optical fiber, etc.) and software, including communication protocols. Early computer buses were parallel electrical wires with multiple hardware connections, but the term is now used for any physical arrangement that provides the same logical function as a parallel electrical busbar. Modern computer buses can use both parallel and bit serial connections, and can be wired in either a multidrop (electrical parallel) or daisy chain topology, or connected by switched hubs, as in the case of Universal Serial Bus (USB). Background and nomenclature Computer systems generally consist of three main parts: * The central processing unit (CPU) that processes data, * The memory that holds the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Video Terminal
A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system. The teletype was an example of an early-day hard-copy terminal and predated the use of a computer screen by decades. Early terminals were inexpensive devices but very slow compared to punched cards or paper tape for input, yet as the technology improved and video displays were introduced, terminals pushed these older forms of interaction from the industry. A related development was time-sharing systems, which evolved in parallel and made up for any inefficiencies in the user's typing ability with the ability to support multiple users on the same machine, each at their own terminal or terminals. The function of a terminal is typically confined to transcription and input of data; a device with significant local, programmable data-processing capability may be called a "smart terminal" or fat client. A term ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Current Loop Interface
For serial communications, a current loop is a communication interface that uses current instead of voltage for signaling. Current loops can be used over moderately long distances (tens of kilometres), and can be interfaced with optically isolated links. There are a variety of such systems, but one based on a 20 mA current level was used by the Teletype Model 33 and was particularly common on minicomputers and early microcomputer which used these as computer terminals. As a result, most computer terminals also supported this standard into the 1980s. History Long before the RS-232 standard, current loops were used to send digital data in serial form for teleprinters. More than two teleprinters could be connected on a single circuit allowing a simple form of networking.E. A. Parr, ''Industrial Control Handbook'', Industrial Press Inc., 1998, , page 648 Older teleprinters used a 60 mA current loop. Later machines, such as the Teletype Model 33, operated on a lower 20&n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-volatile Memory
Non-volatile memory (NVM) or non-volatile storage is a type of computer memory that can retain stored information even after power is removed. In contrast, volatile memory needs constant power in order to retain data. Non-volatile memory typically refers to storage in semiconductor memory chips, which store data in floating-gate memory cells consisting of floating-gate MOSFETs ( metal–oxide–semiconductor field-effect transistors), including flash memory storage such as NAND flash and solid-state drives (SSD). Other examples of non-volatile memory include read-only memory (ROM), EPROM (erasable programmable ROM) and EEPROM (electrically erasable programmable ROM), ferroelectric RAM, most types of computer data storage devices (e.g. disk storage, hard disk drives, optical discs, floppy disks, and magnetic tape), and early computer storage methods such as punched tape and cards. Overview Non-volatile memory is typically used for the task of secondary storage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
N-channel
The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs control the flow of current by the application of a voltage to the gate, which in turn alters the conductivity between the drain and source. FETs are also known as unipolar transistors since they involve single-carrier-type operation. That is, FETs use either electrons (n-channel) or holes (p-channel) as charge carriers in their operation, but not both. Many different types of field effect transistors exist. Field effect transistors generally display very high input impedance at low frequencies. The most widely used field-effect transistor is the MOSFET (metal-oxide-semiconductor field-effect transistor). History The concept of a field-effect transistor (FET) was first patented by Austro-Hungarian physicist Julius Edgar Lilienfeld in 1925 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Punched Card
A punched card (also punch card or punched-card) is a piece of stiff paper that holds digital data represented by the presence or absence of holes in predefined positions. Punched cards were once common in data processing applications or to directly control automated machinery. Punched cards were widely used through much of the 20th century in the data processing industry, where specialized and increasingly complex unit record machines, organized into semiautomatic data processing systems, used punched cards for data input, output, and storage. The IBM 12-row/80-column punched card format came to dominate the industry. Many early digital computers used punched cards as the primary medium for input of both computer programs and data. While punched cards are now obsolete as a storage medium, as of 2012, some voting machines still used punched cards to record votes. They also had a significant cultural impact. History The idea of control and data storage via punched hol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OS/8
OS/8 is the primary operating system used on the Digital Equipment Corporation's PDP-8 minicomputer. PDP-8 operating systems which precede OS/8 include: * R-L Monitor, also referred to as MS/8. * P?S/8, requiring only 4K of memory. * PDP-8 4K Disk Monitor System * PS/8 ("Programming System/8"), requiring 8K. This is what became OS/8 in 1971. Other/related DEC operating systems are OS/78, OS/278, and OS/12. The latter is a virtually identical version of OS/8, and runs on Digital's PDP-12 computer. Digital released OS/8 images for non-commercial purposes which can be emulated through SIMH. Overview OS/8 provides a simple operating environment that is commensurate in complexity and scale with the PDP-8 computers on which it ran. I/O is supported via a series of supplied drivers which uses polled (not interrupt-driven) techniques. The device drivers have to be cleverly written as they can occupy only one or two memory pages of 128 12-bit words, and have to be able to run in any p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baud Rate
In telecommunication and electronics, baud (; symbol: Bd) is a common unit of measurement of symbol rate, which is one of the components that determine the speed of communication over a data channel. It is the unit for symbol rate or modulation rate in symbols per second or pulses per second. It is the number of distinct symbol changes (signalling events) made to the transmission medium per second in a digitally modulated signal or a bd rate line code. Baud is related to ''gross bit rate'', which can be expressed in bits per second. If there are precisely two symbols in the system (typically 0 and 1), then baud and bit per second (bit/s) are equivalent. Naming The baud unit is named after Émile Baudot, the inventor of the Baudot code for telegraphy, and is represented according to the rules for SI units. That is, the first letter of its symbol is uppercase (Bd), but when the unit is spelled out, it should be written in lowercase (baud) except when it begins a sentence. It ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mini-Micro Systems (magazine)
Mini-Micro Systems, a trade magazine, was a computer industry monthly magazine published by Cahners Publishing RELX plc (pronounced "Rel-ex") is a British multinational information and analytics company headquartered in London, England. Its businesses provide scientific, technical and medical information and analytics; legal information and analytics; .... History The magazine's ''Mini-Micro Systems'' title originated in 1976; previously it was named ''Modern Data''. Some of their material was picked up by other computer periodicals. Publication of ''Mini-Micro'' ceased in 1989. When computer periodicals were more numerous, '' The New York Times'' noted that the 1968-originated ''Modern Data'' title benefited from both a change in title and that they successfully "homed in exclusively on the mushrooming small computer field." References External Links * Defunct computer magazines published in the United States Professional and trade magazines {{compu- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Byte (magazine)
''Byte'' (stylized as ''BYTE'') was a microcomputer magazine, influential in the late 1970s and throughout the 1980s because of its wide-ranging editorial coverage. "''Byte'' magazine, the leading publication serving the homebrew market ..." ''Byte'' started in 1975, shortly after the first personal computers appeared as kits advertised in the back of electronics magazines. ''Byte'' was published monthly, with an initial yearly subscription price of $10. Whereas many magazines were dedicated to specific systems or the home or business users' perspective, ''Byte'' covered developments in the entire field of "small computers and software", and sometimes other computing fields such as supercomputers and high-reliability computing. Coverage was in-depth with much technical detail, rather than user-oriented. The company was purchased by McGraw-Hill in 1979, a watershed event that led to the rapid purchase of many of the early computer magazines by larger publishers. By this time t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vectored Interrupt
In computer science, a vectored interrupt is a processing technique in which the interrupting device directs the processor to the appropriate interrupt service routine. This is in contrast to a polled interrupt system, in which a single interrupt service routine must determine the source of the interrupt by checking all potential interrupt sources, a slow and relatively laborious process. Implementation Vectored interrupts are achieved by assigning each interrupting device a unique code, typically four to eight bits in length. When a device interrupts, it sends its unique code over the data bus In computer architecture, a bus (shortened form of the Latin ''omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This ex ... to the processor, telling the processor which interrupt service routine to execute. References {{Reflist Computer architecture Interrup ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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