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IBM 1401 system. From the left: 1402 punch/reader, 1401 processor, 1403 printer.
The IBM 1401, the first member of the IBM 1400 series, was a variable wordlength decimal computer that was announced by IBM on October 5, 1959. It was withdrawn on February 8, 1971.
From the IBM Archives:
The following is the text of an IBM Data Processing Division press fact sheet distributed on October 5, 1959.
The all-transistorized IBM 1401 Data Processing System places the features found in electronic data processing systems at the disposal of smaller businesses, previously limited to the use of conventional punched card equipment. These features include: high speed card punching and reading, magnetic tape input and output, high speed printing, stored program, and arithmetic and logical ability.
The 1401 may be operated as an independent system, in conjunction with IBM punched card equipment, or as auxiliary equipment to IBM 700 or 7000 series systems.
The IBM 1401 was also commonly used as an off-line peripheral controller in many installations of both large Scientific Computers and large Business Computers. In these installations the big computer (e.g., an IBM 7090) did all of its input-output on magnetic tapes and the 1401 was used to format input data from other peripherals (e.g., the punch card reader in the IBM 1402 card reader/punch) on the tapes and transfer output data from the tapes to other peripherals (e.g., the punch card punch in the IBM 1402 card reader/punch or the IBM 1403 lineprinter).
During its lifetime about 20,000 total systems were manufactured (photo), making the IBM 1401 one of IBM's most successful products. From the IBM Archives:
The monthly rental for a 1401 was $2,500 and up, depending on the configuration. By the end of 1961, the number of 1401s installed in the United States alone had reached 2,000 -- representing about one out every four electronic stored-program computers installed by all manufacturers at that time. The number of installed 1401s peaked at more than 10,000 in the mid-1960s, and the system was withdrawn from marketing in February 1971.
Elements within IBM, notably John Haanstra, an executive in charge of 1401 deployment, supported its continuation in larger models for evolving needs (e.g., the IBM 1410) but the 1964 decision at the top to focus resources on the System/360 ended these efforts rather suddenly. To preserve customer investment in 1401 software, IBM pioneered the use of microcode emulation, in the form of ROM, so that some System/360 models could run 1401 programs. Such emulation continued well into the modern era... in some cases, perhaps, until Y2K efforts caused the still-running 1401 code to be rewritten.
During the 1970s, many installations in India and Pakistan used the 1401 and some of today's Indian and Pakistani software entrepreneurs started on this machine. An IBM 1401, the first computer in Pakistan, was installed in Pakistan International Airlines.
A 1401 Restoration Project is in process at the Computer History Museum in Mountain View, California, complete with a "false floor" typical of the mainframe era (and modern data centers), used to hide cabling.[1]
Contents
1 Architecture
2 Software
3 Character and Op codes
4 Hardware implementation
5 Art inspired by IBM 1401
6 References
7 External links
8 Notes
//
Architecture

IBM 1401 Operators Control Panel.
The 1401 used IBM's binary-coded-decimal (BCD) character coding. Each byte (or alphameric character) in the 1401 was represented by six bits, called A, B, 8, 4, 2 and 1. The A and B bits were called zone bits and the 8, 4, 2 and 1 bits were called numeric bits. Associated with each six-bit byte were two other bits, called C for odd parity check and M for word mark,[2] in the following format:
C B A 8 4 2 1 M
The 1401 was available in five memory configurations: 1.4K[3], 2K, 4K, 8K, or 16K (a very small number of 1401s were expanded to 32K by special RPQ - Request for Price Quotation). An optional "Advanced Programming Option" allowed for additional flags for 3 bytes within the first 100.
An IBM 1401 core memory address consisted of three six-bit bytes. The decimal address within 000 to 999 was specified by the 8-4-2-1 bits of these bytes. The zone bits of the high-order byte specified an increment, A 1000, B 2000, A and B 3000, giving an addressability of 4,000 bytes in all. The zone bits of the low-order byte specified increments of 4000, 8000, or 12000, to address 16,000 bytes (with an IBM 1406 memory expansion unit). The zone bits of the middle byte were used to specify index registers, one of many optional features.
Instructions were of six lengths (1, 2, 4, 5, 7, 8). One-byte instructions consisted of only an opcode. These were either defined as one-byte instructions or were chained...(and so on)