RESERVE
Reserves given number of bytes.
RESERVE Size [number]
This command reserves given number of bytes. If it is at the end of the source (there are no instructions below reservation, only labels and other reservations), it affects only with labels above and doesn't generate any data to output file. Otherwise it writes given number of bytes into output file filling them with any data (actually with zeros).
MOV4i &stack SR ; The program stack: RESERVE 10240