I have a single board computer sitting beside me as I type this. It has no display or input on the system. It is, however, the canonical example of a single-board computer, which is almost certainly the unit that will appear in Google if you type in that term.The KIM1 was the first single board computer
In any event, Ian's concern about my counterexamples was that "Again, the ELF and MMD did not have integrated keyboard or screen". So let us make a new definition of "single board computer with keyboard and screen".
However, as one can see in the Wikipedia's article on single-board computers, the MMD-1 did indeed include both a keyboard and a display. Such systems were very common at that time, as they were released with every new microprocessor. For instance, in March 1976, Intel released the SDK-85 as part of the introduction of the 8085. Like the KIM-1, it included both a hex keyboard and LED segment display. Similar systems, the SIM4-01 and SIM8-01, date to 1972, differing only in that they lacked the segmented LED displays, which were only just coming to market at that time.
The KIM-1 was first announced in April 1976 in Byte. You can find it on page 14: https://archive.org/details/byte-magazi ... 04/page/n5 Now if you simply leaf through the magazine, you'll find any number of similar machines that are already shipping. For instance, on page 33 there is the EBKA Familiarizor, which is also based on the 6502 and includes a somewhat different keypad and display, page 34 has a more sophisticated system from TI, and page 39 has the Intercept Jr. based on the Intersil IM6100. Let's read the description of that last one, "...a complete all-CMOS computer on a 10 by 12 inch board. Contains batteries, entry keyboard, 8-digit LED display, RAM and ROM memory..." So this machine doesn't even need to be connected to a power supply, that's built-in as well.
There does not appear to be any definition by which the KIM-1 is the first single board computer. Even if one uses the narrowing definition that requires a keyboard and display - which is certainly *not* part of any accepted definition one can find - the SDK-85 and Intercept Jr. meet all of those requirements were actually shipping before the KIM was even announced. I'm sure there are others from the same era, dating all the way to at least 1975 when the 8080 started volume shipments.