This is what I loved about the PDP-11 series. The instruction opcodes were so painfully obvious you could read them in octal.

I would use a hand punch to create holes in paper tape that was the program. (Just a metal block with holes drilled and a metal dowel to punch the tape).

"Patching the tape" involved finding a section of code that could be "overpunched" to be a jump instruction to the current end of tape where you could punch in a subroutine and a return statement.

If all else failed you'd create a "patch tape" that was read after the original tape and overwrote memory locations.

It was all very convenient since you could "single step" the program from the front panel and watch the registers change.

Life got really sweet when the new teletype had a reader/punch.

Good times.