Originally designed as an electronic accelerator for electromechanical tabulating machines, similar to the IBM 604, it was gradually enhanced with new features and evolved into a first-generation stored program computer (Gamma AET, 1955, then ET, 1957).

Over the course of its ten-year availability, this machine facilitated the transition from electromechanical unit records equipment to computers.

Until the 1950s, Compagnie des Machines Bull, like its rival IBM, primarily marketed punched card tabulators for inventory management, payroll, and accounting.

These tabulators performed arithmetic operations through a series of digit wheels driven by an electro-mechanical device.

[5] In order to increase the calculation speed and avoid delaying the reading of punched cards during more complex operations, an accelerator capable of overcoming electro-mechanical limitations became a necessity.

[5] Starting in 1949, the Bull Company became interested in vacuum tubes for their switching speed compared to adding wheels and electromechanical relays.

The duration of instructions execution varied from 0.6 ms to 10 ms, with a mean time 2 ms.[8][9] The Gamma 3 was connected to the tabulator through a cable plugged in place of its connection panel (where the program instructions were coded); thus, the program would now reside and run on the Gamma 3 computer rather than the tabulator.

Furthermore, despite being electronic, binary, and having a Turing-complete instructions set, the Gamma 3 still lacked the ability to store programs in memory.

[13] As a last upgrade, the magnetic drum was doubled in height in 1957, reaching 16,384 words (98 kB) or 50,000 instructions, and a standalone operator console was included, featuring an oscilloscope CRT display and push buttons to examine memory and single step the code.

[8] The Gamma 3 and 3 ET were subsequently used both in business data processing within large companies and for scientific calculations, notably at the then-emerging CERN and CNRS[1][17] or Air Liquide.

[18] Bull never sold the Gamma 3 in America despite its partnership with Remington Rand - Univac and having a custom version with a 60 Hz power supply.

The circulating memories, denoted from M8 to M15, are implemented using magnetorestrictive delay lines in a separate, dedicated cabinet (ET).

An "Ordonnateur" (ORD) memory cabinet can also be added, providing an extra four groups (4 to 7), each one holding data, none of them executable.

Finally, the drum memory serves as a large swapping device hosting both code and data, and fed from punch cards.

While this increases the execution speed, it also makes far jumps more costly, as a page must first be swapped from the drum to the MC memories with a dedicated instruction ("TB").

[12] The following table describes the instructions with their mnemonics and related machine code: Series must be 0, 1 or 2 (jumps back to the address stored in RNL1) TB (Tambour->Banale) Last position of OF sets T->B or B->T Since the plugboard was mapped to series 3, some extensions and subroutines eventually became shipped as pre-wired plugboard programs.

[24][12] In the later days of the Gamma 3, a high-level language was implemented by a team of students led by professor Pierre Bacchus from University of Lille.

One is exhibited at Technikum museum near Frankfurt,[27] another at the Fédération des Équipes Bull in Angers, France, where it was manufactured,[28] and another one in Museo degli Strumenti per il Calcolo in Pisa, Italy.