There are two kinds of prototyping,these are physical prototyping and vertical prototyping

concerned with the nature of cognitive phenomena across individuals, artefacts and internal and external representations.

How information is acquired from the world and transformed into experiences

Test conditions are the same for every participant in usability Testing.

If you have a block of code you want to execute infinitely   , how can you achieve this without eating up the memory ? 

The goal and profile  of the user who uses the system is called