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IBM 1400 series

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IBM 1401 Data Processing System, the first member of the 1400 series

The IBM 1400 series were second-generation (transistor) mid-range business decimal computers that IBM marketed in the early 1960s. The 1400-series machines stored information in magnetic cores as variable length character strings separated at the left and right by a special flag, called word 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 was the first member of the IBM 1400 series. It was the first computer to deploy over 10,000 units.[1] The IBM 1410 was a similar design, but with a larger address space. The IBM 1460 was logically but not physically identical to a fully optioned 1401 with 16,000 characters of memory, and twice as fast. The 1240 was a banking system, equivalent to the 1440 system with MICR support. The IBM 7010 was logically but not physically identical to a 1410, and twice as fast.

Members of the 1400 series included:

  • IBM 1240 - 1963 "banking system".
  • IBM 1401 - 1959
  • IBM 1410 - 1960
  • IBM 1420 - 1962 "high-speed bank transit system".
  • IBM 1440 - 1962
  • IBM 1450 - 1968 "Bank Data Processing System for small banks".
  • IBM 1460 - 1963
  • IBM 7010 - 1962

Peripherals used with 1400 series machines included:

Compatible systems

IBM provided several models compatible (or nearly so) with the 1401.

  • 1460 was twice as fast, and many special features of 1401 were standard.
  • 1440 was a popular lower-cost alternative, although not fully compatible with the 1401.
  • 1240, 1420, 1450 were systems specially designed for banking.
  • 1410 was a much faster system in the same spirit as 1401, but with significant differences, such as larger memory (up to 100,000 characters), more index registers (fifteen), and additional instructions. A remarkable feature in the pre-microprogramming era was a "compatibility mode" switch that allowed it to run 1401 programs without change.
  • 7010 was a faster and exactly compatible version of 1410.
  • The IBM System/360 Model 30 could be ordered with a 1401 compatibility microprogram feature. Several 1400 series peripherals were adapted for use with System/360.

Honeywell's Honeywell 200 provided approximate 1401 compatibility through a combination of architectural similarity and software support.

Field and character coding

With the 1410 series, the smallest addressable unit in core-storage is called character. The 1410 stores alphameric characters internally in binary-coded decimal (BCD) form, spanning 6 bits called BA8421. When the character is an operation code or is the first character in a field, another bit, called word mark, is included. An odd parity bit, called C, is also included.

Arithmetic is 10-based with the one's position at the high- and the most significant decimal digit at the low-address end of a multi-digit field, thus of ″big-endian″ style. This pertains for both, the (possibly indexed) address calculation for the access of operands and for the various operands of the arithmetic instructions. Whereas an address field in an instruction, designating an operand, is of fixed length (which depends on the size of the storage), the numeric operands of arithmetic instructions may be of arbitrary (positive) length. The word mark approach allows the 1410 to access a field (depending on the instruction to be performed) at either end, so that the most efficient access can be chosen. This way, the compiler of a higher level programming language has to take care of the initial increment of the operand address (by operand length minus 1) e. g. for add, subtract, or multiply instructions.[2]

Programming languages

Programming languages for the 1400 series included Symbolic Programming System (SPS, an assembly language), Autocoder (assembly language), COBOL, FORTRAN, Report Program Generator (RPG), and FARGO.

Retirement

The 1400 series was replaced by System/360 and, later, by low-end machines like the IBM System/3, System/32, System/34, System/36, System/38, and AS/400.

The 1400s were officially withdrawn in the early 1970s, however some 1400-series peripherals were still marketed with third generation systems.

Two 1401 computers have been restored to full operational status at the Computer History Museum.

Notes

  1. ^ Columbia University, Computing History Project, 1401 page
  2. ^ IBM 1410 Principles of Operation.

References

Wikimedia Commons has media related to IBM 1400 series.
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