This paper describes two of the abstract machines used to support the STAB-1 language, and discusses some problems of implementing the language on two different computers, the DEC PDP-11 and CTL's Modular-1. Interpretation of the abstract machine code and direct translation is considered for both computers. KEY WORDS STAB-1 PDP 11 Modular-1 Compilation Interpretation Abstract machines * Professor of Computer Science at the University of Strathclyde. t Part-time M.Sc. student at the University of Strathclyde. $ Recent graduate of the University of Strathclyde. His contribution to this work was carried out as part of a final year project. Group 2: storing instructions SW: SC: Store the 16-bit word at (A+2) in the address pointed to by the word at A. Add 4 to A. Store the 8-bit character in the bottom end of the word at (A+2) in the (byte) address pointed to by the word at A. Add 4 to A. Group 3: monadic instructions FW: FC: NT: NG:Replace the word at the head of the stack by the word it points to. Replace the word at the head of the stack by the byte it points to, extended to full word length by the insertion of zeros at the most significant end. Replace the word at the head of the stack by its 1's complement. Replace the word at the head of the stack by its 2's complement.