Early computers didn’t have operating systems.
You just plugged in a punch card or tape with the program you want to run and the computer executed those exact instructions and nothing else.
Those programs were specifically written for that exact hardware (not even for that model, but for that machine).
To boot up the computer, you had to put a number of switches into the correct position (0 or 1), to bring its registers in the correct state to accept programs.
So you were the BIOS and bootloader, and there was no need for an OS because the userspace programs told the CPU directly what bits to flip.
Early computers didn’t have operating systems.
You just plugged in a punch card or tape with the program you want to run and the computer executed those exact instructions and nothing else.
Those programs were specifically written for that exact hardware (not even for that model, but for that machine).
To boot up the computer, you had to put a number of switches into the correct position (0 or 1), to bring its registers in the correct state to accept programs.
So you were the BIOS and bootloader, and there was no need for an OS because the userspace programs told the CPU directly what bits to flip.