This allows you to control the size of your program's stack (in Kilobytes). The default stack size (64K) should be more than enough for the vast majority of programs. However if your program is heavily recursive or has functions that need a large amount of space for local variables or parameters then you can increase this value up to a maximum of 1024K (1MB). On the other hand you can also reduce the size of your program's stack (not recommended).