It was the evolution of a prototype called the SCAMP (Special Computer APL Machine Portable) that was developed at the IBM Palo Alto Scientific Center in 1973.

In 1973, Bill Lowe was instrumental in fostering an engineering prototype called SCAMP (Special Computer APL Machine Portable) created by Dr. Paul Friedl and a team at the IBM Los Gatos Scientific Center.

[6] The IBM Los Gatos engineering prototype and a design model by IBM Industrial designer Tom Hardy, were utilized internally by Lowe in his early efforts to demonstrate the viability of creating a single-user computer.

[9] In 1973, APL was generally available only on mainframe computers, and most desktop sized microcomputers such as the Wang 2200 or HP 9800 offered only BASIC.

Some configurations of the IBM 5100 had Executable ROS (ROM) and RAM memory totalling more than 64 KB, so a simple bank switching scheme was used.

The actual APL and BASIC interpreters were stored in a separate Language ROS address space which the PALM treats as a peripheral device.

[6] It was the size of a small suitcase, weighed about 55 lb (25 kg), and could be transported in an optional carrying case, hence the "portable" designation.

In 1975, it was an amazing technical accomplishment to package a complete computer with a large amount of ROM and RAM, CRT display, and a tape drive into a machine that small.

Two solutions existed for obtaining hardcopy output: printers such as the IBM 5103, and attaching a typewriter via an interface.

In order to access the port extensions, they needed to be loaded from tape for the APL and BASIC programming languages.

[11] An external video monitor receiver could be connected to the IBM 5100 via a BNC connector on the back panel.

APL had powerful features for manipulating data as vectors and matrices, while the competing HP 9830 had to offer language extensions on an add-on ROM for matrix operations.

The 5100 was based on IBM's innovative concept that, using an emulator written in microcode, a small and relatively cheap computer could run programs already written for much larger, and much more expensive, existing computers, without the time and expense of writing and debugging new programs.