And what would do that “read data off disk, then write other data back”, if not a program? Even if you use a monitor (https://en.wikipedia.org/wiki/Machine_code_monitor) to write a program, that’s still a program.

The only way to avoid that is to hand-punch a tape or something like that (with lots of practice and patience, it may be possible to program a small PROM or write an early floppy by hand)