Doesn't interfere with other activities. One way is to test this is to ask a person to perform two processes simultaneously. If doing two things at once is no harder than doing one thing, one of the tasks must be automatic. For example, if you can talk to me and do mental addition, talking or mental addition must be automatic. Until the balancing becomes automatic, there should be trouble.
Algorithmic processing is step-by step, requires attention.
For example, do alphabet arithmetic. But, with practice, they get fast. Logan says it's because you've stored the answer after practice, so it's retrieval instead of an algorithm. Reading by the whole word method. You don't do well at counting letters because you normally don't process letters when reading.