What best describes the use of visual codes to memorize information?

Mneumonics are great incoders for memorization. The average brain can only memorize up to 7 units of information. So lets say you were given a mix of 21 numbers and letters or for in this case 21 units of information. You could brake this up into 7 chunks of three so your only using 7 units. So people such as myself are able to remember up to a mix of 49 letters and numbers or more (I have not tried more)