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IBM 7330
The IBM 7330 Magnetic Tape Unit was IBM's low-cost tape mass storage system through the 1960s. Part of the IBM 7 track family of tape units, it was used mostly on 1400 series computers and the IBM 7040/7044. The 7330 used magnetic tape up to long wound on reels up to diameter. Data format The tape had seven parallel tracks, six for data and one for parity. Tapes with character data (BCD) were recorded in even parity. Binary tapes used odd parity. (709 manual p. 20) Aluminum strips were glued several feet from the ends of the tape to serve as beginning and end of tape markers. Write protection was provided by a removable plastic ring in the back of the tape reel. A ¾ inch gap between records allowed the mechanism time to stop the tape. At 200 characters per inch, a single 2400-foot tape could store the equivalent of some 50,000 punched card A punched card (also punch card or punched-card) is a piece of stiff paper that holds digital data represented by the pre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Tape
Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use magnetic tape could with relative ease record and playback audio, visual, and binary computer data. Magnetic tape revolutionized sound recording and reproduction and broadcasting. It allowed radio, which had always been broadcast live, to be recorded for later or repeated airing. Since the early 1950s, magnetic tape has been used with computers to store large quantities of data and is still used for backup purposes. Magnetic tape begins to degrade after 10–20 years and therefore is not an ideal medium for long-term archival storage. Durability While good for short-term use, magnetic tape is highly prone to disintegration. Depending on the environment, this process may begin after 10–20 years. Over time, magnetic tape made in the 197 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM 7 Track
IBM's first magnetic-tape data storage devices, introduced in 1952, use what is now generally known as 7-track tape. The magnetic tape is 1/2" wide, and there are six data tracks plus one parity track for a total of seven parallel tracks that span the length of the tape. Data is stored as six-bit characters, with each bit of the character and the additional parity bit stored in a different track. These tape drives were mechanically sophisticated floor-standing drives that used vacuum columns to buffer long U-shaped loops of tape. Between active control of powerful reel motors and vacuum control of these U-shaped tape loops, extremely rapid start and stop of the tape at the tape-to-head interface could be achieved. When active, the two tape reels thus fed tape into or pulled tape out of the vacuum columns, intermittently spinning in rapid, unsynchronized bursts resulting in visually striking action. Stock shots of such vacuum-column tape drives in motion were widely used to r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM 1400 Series
The IBM 1400 series were second-generation (transistor) mid-range business decimal computers that IBM marketed in the early 1960s. The computers were offered to replace tabulating machines like the IBM 407. The 1400-series machines stored information in magnetic cores as variable-length character strings separated on the left by a special bit, called a "wordmark," and on the right by a "record mark." Arithmetic was performed digit-by-digit. Input and output support included punched card, magnetic tape, and high-speed line printers. Disk storage was also available. Many members of the series could be used as independent systems, as extensions to IBM punched-card equipment, or as auxiliary equipment to other computer systems. Some, however, were intended for specific applications or were economical only as independent systems. History The 1401, announced on October 5, 1959, was the first member of the IBM 1400 series. It was the first computer to deploy over 10,000 units. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM 7040
The IBM 7040 was a historic but short-lived model of transistor computer built in the 1960s. History It was announced by IBM in December 1961, but did not ship until April 1963. A later member of the IBM 700/7000 series of scientific computers, it was a scaled-down version of the IBM 7090. It was not fully compatible with the 7090. Some 7090 features, including index registers, character instructions and floating point, were extra-cost options. It also featured a different input/output architecture, based on the IBM 1414 data synchronizer, allowing more modern IBM peripherals to be used. A model designed to be compatible with the 7040 with more performance was announced as the 7044 at the same time. Peter Fagg headed the development of the 7040 under executive Bob O. Evans. A number of IBM 7040 and 7044 computers were shipped, but it was eventually made obsolete by the IBM System/360 family, announced in 1964. The schedule delays caused by IBM's multiple incompatible architec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parity Bit
A parity bit, or check bit, is a bit added to a string of binary code. Parity bits are a simple form of error detecting code. Parity bits are generally applied to the smallest units of a communication protocol, typically 8-bit octets (bytes), although they can also be applied separately to an entire message string of bits. The parity bit ensures that the total number of 1-bits in the string is even or odd. Accordingly, there are two variants of parity bits: even parity bit and odd parity bit. In the case of even parity, for a given set of bits, the bits whose value is 1 are counted. If that count is odd, the parity bit value is set to 1, making the total count of occurrences of 1s in the whole set (including the parity bit) an even number. If the count of 1s in a given set of bits is already even, the parity bit's value is 0. In the case of odd parity, the coding is reversed. For a given set of bits, if the count of bits with a value of 1 is even, the parity bit value is se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Write Protection
Write protection is any physical mechanism that prevents writing, modifying, or erasing data on a device. Most commercial software, audio and video on writeable media is write-protected when distributed. Examples * IBM -inch magnetic tape reels, introduced in the 1950s, had a circular groove on one side of the reel, into which a soft plastic ring had to be placed in order to write on the tape. ("No ring, no write.") * Audio cassettes and VHS videocassettes have tabs on the top/rear edge that can be broken off (uncovered = protected). * 8 and -inch floppies can have, respectively, write-protect and write-enable notches on the right side (8-inch punched = protected; -inch covered/notch not present = protected). A common practice with single-sided floppies was to punch a second notch on the opposite side of the disk to enable use of both sides of the media, creating a flippy disk, so called because one originally had to flip the disk over to use the other side. * -inch floppy ... [...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 equipment, 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 (computing), 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 contr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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