MACRO-11

MACRO-11 is an assembly language with macro facilities for PDP-11 minicomputers from Digital Equipment Corporation (DEC). It is the successor to PAL-11 (Program Assembler Loader), an earlier version of the PDP-11 assembly language without macro facilities.

The MACRO-11 assembly language was designed for the PDP-11 minicomputer family. It was supported on all DEC PDP-11 operating systems. PDP-11 Unix systems also include an assembler (called "as"), structurally similar to MACRO-11 but with different syntax and fewer features. The MACRO-11 assembler (and programs created by it) could also run under the RSX-11 compatibility mode of VAX/VMS.^[1]

Programming example

A complete "Hello, world!" program in PDP-11 macro assembler, to run under RT-11:

 .TITLE HELLO WORLD .MCALL .TTYOUT,.EXIT HELLO:: MOV #MSG,R1 ;STARTING ADDRESS OF STRING 1$: MOVB (R1)+,R0 ;FETCH NEXT CHARACTER BEQ DONE ;IF ZERO, EXIT LOOP .TTYOUT ;OTHERWISE PRINT IT BR 1$ ;REPEAT LOOP DONE: .EXIT MSG: .ASCIZ /Hello, world!/ .END HELLO 

The .MCALL pseudo-op warns the assembler that the code will be using the .TTYOUT and .EXIT macros. The .TTYOUT and .EXIT macros are defined in the standard system macro library to expand to the EMT instructions to call the RT-11 monitor to perform the requested functions.

If this file is HELLO.MAC, the RT-11 commands to assemble, link and run (with console output shown) are as follows:

.MACRO HELLO ERRORS DETECTED: 0 .LINK HELLO .R HELLO Hello, world! . 

(The RT-11 command prompt is ".")

For a more complicated example of MACRO-11 code, two examples chosen at random are Kevin Murrell's KPUN.MAC, or Farba Research's JULIAN routine. More extensive libraries of PDP-11 code can be found in the Metalab freeware and Trailing Edge archives.^[2][3]

References

External links

• Original documentation (RSX11M_V2)
• Michael Singer, PDP-11. Assembler Language Programming and Machine Organization, John Wiley & Sons, NY: 1980.