The "first" microcomputer "kits" (MITS, IMSAI, Pertec, Scelbi) were all machine-programmed in 'native' binary code via front-panel toggle switches; UP for "1" and DOWN for "O", as were the DEC PDP-series (pink & black), although "boot-strap" loading through RS-232 Teletype paper-tape was popular.
Of course, you had to first toggle in the codes to cause the paper-tape reader to work.
(On the IBM 650, it was toggle in the codes to cause the punched-card reader to run).
Today, that's called the BIOS.