Used on some machines which didn’t have ability to save return address. relevant for registers/stacks?
Before calling the subroutine, put the program counter’s current location in the accumulator.
At start of subroutine, take the location in the accumulator, add to it (eg just 1) and write this to the end of the subroutine CODE.
Then when subroutine ends, can go back.
Limitations: slow because writes to memory, not register or stack. also can’t do recursion.