HandShake is a solution for many students and hobbyists who have to look around the world to find a free or low cost Assembly program.
All source code is available.
This is PIC 16Cxx assembler made by Microchip Technology. Jeff Frohwein SX Cross Assembler from Scenix. Here is the source code for both the assembler and simulator. Here can be found his assembler and disassembler for 12 and 14-bit PIC chips. It can output IHX16 and IHX8M formats.