Turing machine for binary increment

This machine increments a binary number by one. State qScan moves right over the input until it reaches a blank B immediately after the final digit. It then moves one cell left and enters qCarry. In qCarry, every trailing 1 is replaced by 0 while the head moves left, carrying the addition toward the most significant bit. When it finds a 0, the machine writes 1 and accepts. If it instead finds a blank, the original word consisted entirely of 1s, so it writes a new leading 1. For example, 1011 becomes 1100 and 111 becomes 1000. Each edge label makes the tape operation explicit.