No need to #include NXTDefs.h since the compiler does it for you automatically.
The set opcode lets you set a variable to a word-sized (or smaller) constant value. It is beneficial only to the extent that it does not require that you have a variable in your dataspace that stores that particular constant value so that you can mov it into the place where it is needed. With mov even if you use a constant as the source value it actually requires a variable in the VM so the compiler dutifully creates a variable in the dataspace with a static initialization value equal to whatever constant value you used in your code. If you are initializing an int to 53 then you could use set and save a variable. The compiler automatically unifies these auto-constant variables that it creates so if you use