The National Radio Institute 832 was probably the first commercially available computer kit. It was sold as part of a correspondence computer course.

This is what Lou Frenzel, the designer of the NRI-832, have to say about his creation:

"I did design the 832 back in 1970-71 time period. It was part of a home study course on computers offered by National Radio Institute, a school owned by publisher McGraw Hill. It was delivered as a series of 5 if I remember correctly.

The memory was a diode switch matrix with 16 bytes programmable with slide switches. It also had an additional 16 bytes of TTL SRAM, which was very expensive at the time. It was made with TTL digital logic but I couldn't bring myself to use any of the older but cheaper RTL or DTL chips.

All processing was done serially with a total of 8 instructions. Amazingly, you could program almost anything if you could get it into the limited memory. This turned out to be a very popular course and kit surprising all of us at the time. We packaged the kits ourselves.

NRI went out of business in 1999 but McGraw Hill is still around, but I imagine all that 832 stuff is long gone."