IBM 1401

The IBM 1401, announced in 1959, was the first computer widely adopted by businesses around the world. It marked the transition between the era of mechanical punched card machines and that of modern computing. At that time, business data processing—inventory, billing, customer accounts, payroll—was performed by passing stacks of punched cards through electromechanical machines that sorted, calculated, collated, and totaled. These operations were determined by manually wired control panels. Mainframe computers with vacuum tubes certainly offered flexible stored-program capability and magnetic tape storage, but their cost made them inaccessible to most businesses. By the mid-1960s, half of all computers in service worldwide were IBM 1401s or members of its family.

The story of the 1401 began in 1957, when IBM France and IBM Germany developed a prototype transistorized “universal accounting machine” (WWAM) in response to a European competitor. Despite using a control panel, the entry-level configuration proved too expensive. In Endicott, New York, a bold system architect, Fran Underwood, discovered that he could economically replace the control panel with stored-program control. Retaining the WWAM’s data paths, he designed an instruction set suited to business applications and named the new computer SPACE (Stored-Program Accounting & Calculating Equipment).

SPACE development was led by Charles Branscomb, who expanded the team to 60 engineers working around the clock. He integrated a printer under development, discouraged superfluous features, and met cost targets for the entry-level system. By mid-1959, with a working prototype and sales training underway, the machine, officially renamed IBM 1401, was poised to revolutionize the business market.

On October 5, 1959, IBM announced the 1401 via closed-circuit television to 50,000 participants in 104 different locations. In just five weeks, 5,200 systems were ordered, exceeding projections for the product’s entire lifetime and surpassing the total number of commercial computers then in service worldwide. A year later, the first system was delivered to Time-Life, which transferred 60 million punched cards to a few hundred magnetic tapes. The tape-equipped 1401 systems thus freed users from a seven-decade-old practice: storing data on punched cards.

In 1962, 1401 revenues exceeded those of traditional accounting machines. In 1965, the 1401 and its family (models 1410, 1440, 1460, and 7010) represented half of all computers worldwide, reaching a peak of 16,000 systems in 1967. The majority of 1401s were leased. An entry-level system leased for $2,500 per month, equivalent to three accounting machines and a calculator. A typical system leased for $6,500 per month, or could be purchased for $500,000—approximately one-tenth the cost of a mainframe computer.

Considered a “small system” computer, a 1401 weighed between 2 and 3 tons, consumed up to 14,000 watts, and contained approximately half a million parts. Maintained primarily by IBM customer engineers, these systems were renowned for their reliability and often operated around the clock.

Technically, the 1401 relied on serial processing of digits and characters. During its 11.5-microsecond clock cycle, an instruction could add two decimal digits or process a character for input, output, or formatting for printing. Variable-length numbers and strings were stored at one digit or character per memory position. Memory size ranged from 1,400 to 16,000 positions, each 8 bits wide—6 bits for the character, 1 bit to mark the end of a number or string, 1 parity bit.

The 1401’s processor operated at 87,000 cycles per second. For comparison, a current 3-gigahertz PC can add two 20-digit numbers approximately one million times faster than a 1401. The machine used inexpensive germanium alloy-junction transistors and point-contact diodes, mounted on approximately 4,000 SMS (Standard Modular System) cards. The ferrite core memory, consisting of a stack of grids of tiny magnetic rings threaded with fine wires, cost approximately 60 cents per bit—400 million times more expensive than current RAM.

The 1401’s success was largely due to its peripherals: the 1403 chain printer, whose speed (600 lines/minute, rapid skipping) and exceptional print quality (horizontally rotating interchangeable chain) made it an industry standard; the 1402 card reader-punch (800 and 250 cards/minute); and the mainframe-type 729 magnetic tape drives (15 million characters per reel). The RAMAC 1405 disk drive (20 million characters) and an optical bank check reader were available from 1961.

On the software side, IBM offered assemblers for machine language programming (Autocoder, SPS), compilers for Fortran, COBOL, and RPG (Report Program Generator) languages, as well as sorting and input-output utilities. IBM did not develop an operating system for the 1401, but created one for the 1410.

In late 1964, Honeywell challenged IBM’s market dominance by announcing the H200, faster and more powerful, accompanied by its Liberator software capable of running 1401 programs without modification. In 1961, IBM began planning the unification of its many computer lines. The System/360, announced in April 1964, consolidated software, peripherals, and support into a family of compatible computers. A key technology was the flexible control store that allowed its entry-level model, the Model 30, to competitively execute 1401 programs, thus countering the H200. The 1401 emulation also allowed IBM to deliver Model 30s when S/360 system software fell behind schedule.

While development of the 1401 family slowed after the S/360 announcement, its members remained more numerous than S/360s until 1968. IBM continued to offer the 1401 until 1971, and PC emulators are available today.

The 1401 also leaves an unexpected legacy in the arts. The machine could produce music by melodically activating the 1403’s print hammers or by modulating its radio wave emissions picked up by an AM receiver. Inspired by a recording of radio music made during a 1401 decommissioning ceremony in 1971, an Icelandic composer wrote a 60-movement orchestration in 2001 entitled IBM 1401: A User’s Manual (available on Spotify, Apple Music, etc.). Finally, in the 1964 film “Dr. Strangelove”, actor Peter Sellers makes his first appearance in front of a 1403.

The IBM 1401 continues to fascinate computing enthusiasts. Volunteers at the Computer History Museum, including a dozen former IBM customer engineers, have devoted more than 40,000 hours to restoring two 1401s, one acquired in 2003 from a German garage and the other in 2008 from a Connecticut home (where it had operated until 1995).