The processes are so similar that cassette boot programs can usually be transferred directly to disk and vice-versa. A bug in early operating systems requires the booted program to turn off the cassette motor with the following command. The Atari 800 has two cartridge slots. All other models have only one. If a cartridge is inserted in a slot it will disable any RAM in the same area.
Cartridges use the last six bytes for boot information.
A minimum of an RTS instruction is required. The third byte of the cartridge tailer is used by the OS to check for the presence of a cartridge. This byte must be zero. A 16K cartridge will use both cartridge areas and the cartridge B tailer area can be used for program code. Moreover, both chip sockets have identical pin assignments.