;-*-MIDAS-*-
        TITLE    SUDOKU SOLVER

A=1                                    ;Define ACs as universal registers
B=2                                    ;from A to E
C=3
D=4
E=5
X=10                                   ;X and Y are used for indexing
Y=11                                   ;loops etc.
P=17                                   ;Define P as the stack pointer. 

PDLLEN==20                             ;Set the size of the stack to 20 words.
PDL:    BLOCK PDLLEN                   ;Reserve the stack memory
BPTR==440700                           ;Define a byte pointer.

CHTTYO==1                              ;Define a channel for TTY output.

JCL:    BLOCK 30                       ;Reserve space for the command line.
FNAME1: BLOCK 15                       ;The first part of the file name.
FNAME2: BLOCK 15                       ;The second file name. 

START:  MOVE  P,[-PDLLEN,,PDL-1]       ;Initialize the stack.
        SETZM JCL                      ;Zero out the JCL
        MOVE  A,[JCL,,JCL+30]
        BLT   A,JCL+30
        .OPEN CHTTYO,[.UAO,,'TTY]      ;Open an output channel on the TTY.
         .LOSE %LSFIL                  ;Gobble up any errors.
        PUSHJ P,GETJCL                 ;Read the command line.
        MOVE  A,[BPTR,,HELLO]          ;Load A with a byte pointer to HELLO.
        PUSHJ P,OUTSTR                 ;Print the out string.
        MOVE  A,[BPTR,,JCL]            ;Read the parameter.
        PUSHJ P,PUTLN                  ;Print the rest of the line.
        JRST  DONE                     ;Jump to the end of the program.

;Subroutine to read the JCL from DDT and get the command line parameters.
;Clobbers B, C and D.
GETJCL: .BREAK 12,[..RJCL,,JCL]        ;Get the JCL
        MOVE B,[BPTR,,JCL]             ;Load the command parameters.
        MOVE C,[BPTR,,FNAME1]          ;Set a pointer to store the first parameter.
JCLL1:  ILDB  D,B                      ;Load the next character.
        JUMPE D,FN2                    ;Exit the loop, if null.
        CAIN  D,30                     ;Jump to next parameter word, if
        CAIL  D,140                    ;Check, if the char is > 96.
         SUBI D,40                     ;Make sure that the code is always < 96
        SUBI  D,40                     ;Convert the char to SIXBIT.
        IDBP  D,C                      ;Deposit the converter value in FNAME1.
        JRST  JCLL1                    ;Loop back to read the next character.
FN2:    MOVE  C,[BPTR,,FNAME2]         ;Load a pointer to FNAME2 into C.
        
        POPJ  P,                       ;Return from routine.
;Subroutine to print a string of text on the output.
; Clobbers A and B.
OUTSTR: HRLI  A,BPTR                   ;Ensure, A is a byte pointer.
OUT:    ILDB  B,A                      ;Load the next byte from A.
        JUMPE B,OUTEX                  ;Exit the routine, if all bytes are done.
        .IOT  CHTTYO,B                 ;Print a character.
        JRST  OUT                      ;Jump back to print the next character.
OUTEX:  POPJ  P,                       ;Return from the output routine.

;Subroutine to print an entire line of text, including a line break.
;Clobbers A and B.
PUTLN:  PUSHJ P,OUTSTR                 ;Calls the OUTSTR subroutine
        .IOT  CHTTYO,[^M]              ;Print a carriage return
        .IOT  CHTTYO,[^J]              ;and a new line
        POPJ  P,                       ;before returning.

DONE:   .LOGOUT  2,                    ;Exit point for the program.
HELLO:  ASCIZ  /HELLO /           ;Define example string.  
END     START