operating system ROM machine language CP/M floppy disk
The Altair, and early clones, were relatively difficult to use. The machines contained no operating system in ROM, so starting it up required a machine language program to be entered by hand via front-panel switches, one location at a time. The program was typically a small driver for an attached cassette tape reader, which would then be used to read in another "real" program. Later systems added bootstrapping code to improve this process, and the machines became almost universally associated with the CP/M operating system, loaded from floppy disk.
