You did Modular Arithmetic when you were thinking about hours on a clock and someone said “add 5 to 10” and you said “Oh it’s 3 (10+5=3).
For “mod 2”, we have two values. We must start with zero, so we have {0,1}.
- 0+0=0
- 0+1=1
- 1+0=1
- 1+1=0
After staring at those results for a few seconds you might notice that addition of the same number results in zero and addition of different numbers results in one.
Rob Sterling 