Order the stages of the task 'read a number from the keyboard, add one, and store the result' as the information flows through the machine.

1. A keypress arrives as an I/O event and raises an interrupt
2. The character is encoded as bits and placed in main memory
3. The CPU fetches the add instruction, checking the cache first
4. The ALU performs the addition inside the data path
5. The result is stored back to main memory

Every layer of the course appears once, in order: I/O, encoding, the memory hierarchy, the data path and ALU, then memory again. Expecting the addition before the fetch skips the fact that the add instruction is itself data that has to be brought in.