This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
Transferring Applesoft programs on an Apple II to QBASIC, GW-BASIC, etc. on the PC is mainly a matter of moving a text copy of the program to the PC. (To make a text copy of an Apple II program, you LIST the program to a Text file. See Q&A 017 above.) On the PC, you bring the A2 program text into your BASIC editor. BASICs available on a PC are not 100% compatible with Applesoft. Once you can list the Applesoft program on the PC under QBASIC (or whatever), you will, almost certainly, need to modify it. It will be necessary to replace some Applesoft commands with their PC BASIC equivalents. Some commands are very similar but differ slightly in syntax; and you are likely to find that some conventions, such as the numerical value of "True" from boolean tests, are different. The more an Applesoft program is "pure BASIC", the easier it will be to get it working on a PC. Programs which employ lots of PEEKs and POKEs, do monitor CALLs, and access other features specific to the Apple II will be more troublesome.