Its a while
back but I seem to remember in BASIC you replaced a set of line
numbers with another of the same range but different code.
Blimey, I've never seen that.
A lot of disk-based BASICs had a statement that would merge a program from
disk in this way. Sometimes the program had to be saved in ASCII, not tokenised,
the BASIC interpretter then essentially read the file as if you were typing it on the
keyboard. So program lines would indeed replace those with the same line number.
One of the extension ROMs for HPL on the HP9825 (a BASIC-like language) had
a command to store a string as a program line. It could be used within a program,
thus leading to an official way to have self-modifying code.
-tony