I have been trying to compile this program using tasm .model tiny .data .code mov ax,f000h end And I get this error E:\zzzz1\lab>tasm test3.asm Turbo Assembler Version 3.1 Copyright (c) 1988, 1992 Borland International Assembling file: test3.asm **Error** test3.asm(5) Undefined symbol: F000H Error messages: 1 Warning messages: None Passes: 1 Remaining memory: 459k And another question is how do I halt the processor I tried "hlt", but when the code runs it pops up a dialog which says illegal instruction.