I guess this is a philosophical general programming question, but since it is about Arduino IDE, I post it here.
I've managed to write some test code after getting to know some basics of AVR assembly and registers, thanx to help I got here, for which I am grateful.
Code is about communicating to TM1637 7-seg display using assembly on ATtiny13, and I saved quite a lot of memory thanx to westfw's help (saving about 150 bytes so far).
BUT, after compiling and uploading a nice working version of this test code, I saved source files to archive named "this works", and after some minor changes in code, it does NOT work, okay - that's normal.
What drives me crazy, is that now, whenever I try to compile&upload this good working version I extracted from archive, it DOES NOT work.
After upload, TM1637 displays some trash and after unplugging/plugging back the USB which is powering my Arduino&ATtiny, TM1637 displays nothing.
Other sketches using TM1637 work fine so the hardware is not dead, but this test code I made, and which once worked (tested it successfully few times before archiving it to RAR) no longer works!
I guess I'll get "show us the damn code" comments but I don't have it with me now and I cannot possibly see how the code can have anything to do with this problem.