I had my first chance to write computer code in the fall of 1977, at age 13.
It's been nearly thirty years since then, so I am posting some of the more interesting code I have written.
In a college class, I had to write an simulator for the 8080 instruction set. I tested it by running a copy of the TRS-80 Model 100 ROM, and found a bug in my DAA (decimal adjust) instruction because the Model 100 used BCD (binary coded decimal) arithmetic.
Here is the simulator, and an "extended" version which was another assignment in that class.
One of my projects was to optimize the ROM in the old Colecovision video game system. I have managed to optimize 1K out of the 8K of code, and am working on a joystick tester. Here is a version of that code:
coleco29.asm - Optimized ColecoVision ROM
test6.asm - Controller tester