Writes the current BASIC program in memory to a file
Implemented by: dartmouth4, hptsb, decbasic, a2int, Applesoft, TI994, CBM, Atari, msatari, level3, colordisk, Sinclair, Atom, BBC, GWBASIC, MSX, bwbasic, bw32, ABasiC, minibasicjs, EndBASIC
With variations: ti994ext (added functionlity and protection)
Also written as: