// Input number; output its residue mod 2
         INP          // read input into accumulator
loop1    STA save_acc // save accumulator (see note below)
         SUB k128     // keep subtracting 128 until acc < 0
         BRP loop1
         LDA save_acc // save_acc holds a number in range 0..127
loop2    STA save_acc
         SUB k16      // keep subtracting 16 until acc < 0
         BRP loop2
         LDA save_acc // save_acc holds a number in range 0..15
loop3    STA save_acc
         SUB k2       // keep subtracting 2 until acc < 0
         BRP loop3
         LDA save_acc // save_acc holds 0 or 1, the result
write    OUT          // output result
         HLT
k2       DAT 2
k16      DAT 16
k128     DAT 128
save_acc DAT
// end