IBM 1400 series | 1959~1963

IBM 1400

 


The IBM 1400 series was a second-generation (transistor-based) mid-sized business decimal computer marketed by IBM in the early 1960s, intended to replace accounting machines such as the IBM 407. These computers stored information in magnetic core memory, were composed of variable-length character strings, and featured a "word mark" special bit on the left side and a "record mark" on the right side of the string. Arithmetic operations were performed on a digit-by-digit basis. Input and output support included punch cards, magnetic tapes, high-speed line printers, and disk storage devices were also available.

Many models in the 1400 series could be used either as standalone systems, as extensions of IBM punch card equipment, or as peripheral equipment for other computer systems. However, some models were specifically designed for certain applications or were economically suited only as standalone systems.

History
The IBM 1401 was announced on October 5, 1959, as the first model in the 1400 series and became the first computer with more than 10,000 units shipped. The IBM 1410 had a similar design but offered a larger address space. The IBM 1460 was logically the same as the 1401 but came with all options included and had double the memory capacity at 16,000 characters, making it twice as fast. The IBM 1240 was designed for banking systems, and the IBM 1440 matched the MICR support of the IBM 1440 system. The IBM 7010 was logically the same as the 1410 but twice as fast.

Key Models in the 1400 Series

  • IBM 1240 – 1963, designed for banking systems
  • IBM 1401 – 1959
  • IBM 1410 – 1960
  • IBM 1420 – 1962, high-speed banking conversion system
  • IBM 1440 – 1962
  • IBM 1450 – 1968, small-scale banking data processing system
  • IBM 1460 – 1963
  • IBM 7010 – 1962

Peripherals
The peripherals used with the 1400 series included:

  • Card readers/punches: IBM 1402, IBM 1442, IBM 1444
  • Printers: IBM 1403, IBM 1404, IBM 1443, IBM 1445
  • 7-track tape drives: IBM 729, IBM 7330, IBM 7335
  • Disk drives: IBM 1301, IBM 1311, IBM 1405 RAMAC
  • Check processing: IBM 1210
  • Paper tape I/O
  • Console typewriters: IBM 1407, IBM 1447

Compatible Systems
IBM offered several models compatible with the 1401:

  • IBM 1460: Twice as fast with many features of the 1401 offered as standard.
  • IBM 1440: A popular lower-cost alternative, though not fully compatible with the 1401.
  • IBM 1240, 1420, 1450: Systems designed specifically for banking.
  • IBM 1410: Similar to the 1401 but faster with larger memory (up to 100,000 characters), 15 more index registers, and additional instructions. The 1410 had a "compatibility mode" switch allowing 1401 programs to run unchanged.
  • IBM 7010: A faster, fully compatible version of the 1410.
  • IBM System/360 Model 30: Could provide microprogramming functionality compatible with the 1401. Several 1400 series peripherals were adapted to be compatible with the System/360.
  • Honeywell 200: Offered compatibility similar to the 1401 through architecture and software support.

Field and Character Coding
In the 1400 series, the smallest addressable unit in the core memory was called a "character." The 1400 used a 6-bit binary-coded decimal (BCD) format for internal storage of letters and numbers. When the character was an operation code or the first character of a field, it included an additional bit called the "word mark," along with another bit called the "C" bit for odd parity.

Arithmetic operations were based on decimal arithmetic, with multi-digit fields storing the most significant digit at the low address end and the least significant digit at the high address end, a "big-endian" style. The address field had a fixed length, depending on the storage size, and the numeric operands for arithmetic instructions could have arbitrary lengths. The word mark method in the 1410 allowed efficient access to fields by permitting access from both ends, making it possible to choose the most efficient approach.

Programming Languages
The 1400 series supported various programming languages including the Symbolic Programming System (SPS), Autocoder (a more complete assembly language), COBOL, FORTRAN, RPG (Report Program Generator), and FARGO.

Decommissioning
The 1400 series was replaced by the IBM System/360, and later by low-cost systems such as the IBM System/3, System/32, System/34, System/36, System/38, and AS/400. The 1400 series was officially decommissioned in the early 1970s, though some 1400 series peripherals were still sold with third-generation systems.

Currently, two fully restored IBM 1401 computers are operational at a computer history museum.

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