1. My Empire game was written in assembler on the PDP-11. To port it to the IBM PC, I rewrote it line by line into C.

2. FutureNet's schematic editor for the IBM PC was a very large assembler program. It was written in assembler because there was no other way to make it fit on the PC. I converted it line by line into C so it would run on a Sun. It took a couple months.

3. I converted some of the Optlink linker, a 32 bit Windows linker, into C. The main difficulty, though, was there was no test suite and it was very very hard to get right. I got maybe 10% of it converted. I eventually abandoned the project because 32 bit Windows code is now obsolete. The other hard part of the project was it was not conventionally divided up into functions. Code would jump into the middle of other functions. Another problem with it was its use of macros and conditional assembly was so hard to decipher that I would assemble the code, run it through my disassembler, and use the latter as my starting point. (Macros are Spawn of the Devil.)