Remove stack saves of register F

Hoping to get rid of the "unknown system call name" error.

.git-monitor_after.sh

@@ -0,0 +1,26 @@
+#!/bin/sh
+# Copies the source files to the ITS system
+
+MLFTP="/opt/pidp10/bin/mlftp"
+
+SOURCEFILE="./src/sudoku.s"
+TARGETFILE="SUDOKU 1 JALI;"
+PUZZLEFILE="./src/puzzle_1.sudoku"
+PUZZLETARGET="PUZZL1 SUDOKU JALI;"
+
+
+# Functions
+log_message() {
+  local level=$1
+  local message=$2
+  timestamp=$(date +'%Y-%m-%d %H:%M:%S')
+  #echo "$timestamp [$level] $message" >> "$LOG_FILE"
+  echo "$timestamp [$level] $message"  # Also print to console (optional)
+}
+
+# Main execution
+log_message "INFO" "Uploading $SOURCEFILE to $TARGETFILE on ITS"
+$MLFTP -w its "$TARGETFILE" $SOURCEFILE
+
+log_message "INFO" "Uploading $PUZZLEFILE to $PUZZLETARGET on ITS"
+$MLFTP -w its "$PUZZLETARGET" $PUZZLEFILE

.gitignore

@@ -0,0 +1 @@
+.git-monitor-last-commit

.layout.tmux

@@ -0,0 +1,14 @@
+#!/usr/bin/zsh
+# Create a layout for development on the PDP-10
+RPDP=$(where rpdp)
+
+# Split the window at the bottom and open a 
+$MUX split-window -v -l 8 -t ${SESSIONID}:0 telnet pidp10.local 1025
+
+# Split again, and connect via ssh to the host machine
+$MUX split-window -h -t ${SESSIONID}:0 ssh pidp10.local
+
+# Finally, start an instance of the Knight-TV console
+if [[ -v RPDP ]]; then
+  $RPDP tvcon
+fi

README.md

@@ -141,6 +141,71 @@ And that's it.
 
 ## Using the PDP-10 to solve the Sudoku
 
-The PDP-10 should be able to solve the sudoku using backtracking. The above
-algorithm will be implemented directly in PDP-10 assembly, using the MIDAS
-assembler, of the ITS operating system.
+In order to run this program, you need a working PDP-10 simulator (or, if you
+are a very lucky person,the real thing). You can either use the
+[PiDP-10 kit](https://obsolescence.wixsite.com/obsolescence/pidp10), or a
+Raspberry Pi 5 to run it on. The PiDP-10 can be run on any Raspberry 5 computer,
+even without the front panel, but having the front panel is fancier. You can
+also run [simh](https://opensimh.org/) on a PC, but that would only be half the
+fun.
+
+The PiDP-10 shold be booted into ITS, as this is the OS, this project is running
+against. Now the only thing you need to do, is copy the source code files into
+the file system of your PiDP-10. You can do this by using the `mlftp` tool,
+installed on the machine your simulator runs on. You clone the repository and
+run the following commands from the command line:
+
+```bash
+/opt/pidp10/bin/mlftp -w ITS "SUDOKU 1 JALI;" ./src/sudoku.s
+/opt/pidp10/bin/mlftp -w ITS "PUZZL1 SUDOKU JALI;" ./src/puzzle_1.sudoku
+```
+
+This will copy the source code file, and the example puzzle file onto the
+PiDP-10. Remmber to change the directory name in the ITS path form `JALI` to the
+directory you want to copy to.
+
+You can now edit both files in EMACS on the PiDP-10. However, if you prefer to
+edit your code in a somewhat more modern environment (your favourite IDE, for
+example), consider installing the
+[git-monitor](https://gitea.orca-central.de/jali/PiDP10Services) on your
+PiDP-10's host system. The monitor is a service written in
+[bash](https://www.gnu.org/software/bash/), that will clone your project
+repositories and then monitor a given branch for new commits. On new commits it
+pulls them, and runs the script `.git-monitor_after.sh`, which in turn, contains
+the upload commands for ITS. This way, you can automatically update your source
+code in ITS, even when you are working on a modern machine.
+
+## Building and running
+
+Log into ITS with your developers user name by typing `USERNAME$U` (where `$` is
+the ESC-Key), If you are a *luser*: Type `:LOGIN USERNAME` and swap `USERNAME`
+for your *actual* username. Confirm with `Enter`.
+
+Now you can build the sudoku solver by invoking MIDAS in DDT:
+
+```
+:MIDAS TS SUDOKU_SUDOKU
+```
+
+This will instruct MIDAS to create a relocatable binary (TS) from the latest
+version of the `SUDOKU` file, and store it in a file named `TS SUDOKU` in the
+current directory. If this succeded, listing the files with `:LISTF` (or
+`CTRL+F`, if you're not a turist), should look something like this:
+
+```
+KA    JALI
+FREE BLOCKS #2=154 #3=169 #0=156 #1=171
+  1  PUZZL1  SUDOKU 1 ! 9/21/2025 22:02:04
+  3  SUDOKU  1      1 ! 9/21/2025 22:02:02
+  1  TS      SUDOKU 1 ! 9/21/2025 23:25:09
+```
+
+To invoke the solver run it with:
+
+```
+:SUDOKU PUZZL1 SUDOKU
+```
+
+This will pass the file `PUZZL1 SUDOKU` to the program, and start to solve it.
+
+The result will be printed on the screen (once the project is finished).

src/SUDOKU.MID

@@ -1,97 +0,0 @@
-;-*-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==30                             ;Set the size of the stack to 30 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.
-
-;Print flags
-;Allows to change the beavihour of the OUTSTR and PUTLN subroutines.
-;The different bits in the word have different meanings.
-;Flags:
-; 001 - SIXBIT: Prints the next character as a SIXBIT char, instead of ASCII, if set.
-PFLAGS: BLOCK 1
-
-START:  MOVE  P,[-PDLLEN,,PDL-1]       ;Initialize the stack.
-        .OPEN CHTTYO,[.UAO,,'TTY]      ;Open an output channel on the TTY.
-         .LOSE %LSFIL                  ;Gobble up any errors.
-        MOVEI A,001                    ;Initialize the print flag
-        MOVEM A,PFLAGS                 ;to print SIXBIT
-        PUSHJ P,GETJCL                 ;Read the command line.
-        MOVE  A,[BPTR,,FNAME1]         ;Read the parameter.
-        PUSHJ P,PUTLN                  ;Print the file name
-        MOVE  A,[BPTR,,FNAME2]         ;Print the second file name.
-        PUSHJ P,PUTLN
-        JRST  DONE                     ;Jump to the end of the program.
-
-;Subroutine to read the JCL from DDT and get the command line parameters.
-GETJCL: PUSH  P,A                      ;Save the register A.
-        PUSH  P,B                      ;Save the register B.
-        SETZM JCL                      ;Zero out the JCL
-        MOVE  A,[JCL,,JCL+30]
-        BLT   A,JCL+30
-        .BREAK 12,[..RJCL,,JCL]        ;Request the JCL.
-        MOVE  A,[BPTR,,JCL]            ;Load the command parameters into A.
-        MOVE  B,[BPTR,,FNAME1]         ;Pointer to the first file name.
-        PUSHJ P,TOSIXB                 ;Transfer the first word into FNAME1
-        MOVE  B,[BPTR,,FNAME2]         ;Pointer to the second file name.
-        PUSHJ P,TOSIXB                 ;Transfer the second word into FNAME2
-        POP   P,B                      ;Restore the B register.
-        POP   P,A                      ;Restore the A register.
-        POPJ  P,                       ;Return from routine.
-        
-;Subroutine to convert an ASCII string into SIXBIT. Takes a byte
-;pointer in A and B, where A is the source and B is the destination.
-TOSIXB: PUSH  P,D                     ;Store the contents of register D.
-TOSLP:  ILDB  D,A                     ;Load the next character from A.
-        JUMPE D,TOSEN                 ;Exit the loop, if charachter is null.
-        CAIN  D,40                    ;If the character is a whitespace,
-        JUMPA TOSEN                   ;exit the loop.
-        CAIL  D,140                   ;If the character is > 96,
-         SUBI D,40                    ;then cut it down, so it's in range.
-        SUBI  D,40                    ;Convert 32..95 to 0..63
-        IDPB  D,B                     ;Deposit the character in the destination.
-        JRST  TOSLP                   ;Repeat with next character.
-TOSEN:  POP   P,D                     ;Restore the D register.
-        POPJ  P,                      ;Return from function.
-
-;Subroutine to print a string of text on the output.
-;Clobbers A.
-OUTSTR: PUSH  P,B                      ;Save register B.
-        PUSH  P,D                      ;Save register D.
-        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.
-        MOVE  D,PFLAGS                 ;Load the print flags.
-        TRNE  D,001                    ;Test, if the SIXBIT flag is set.
-         ADDI B,40                     ;Convert SIXBIT to ASCII.
-        .IOT  CHTTYO,B                 ;Print a character.
-        JRST  OUT                      ;Jump back to print the next character.
-OUTEX:  POP   P,D                      ;Restore D to its original value.
-        POP   P,B                      ;Restore B to its original value.
-        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.
-END     START

src/sudoku.s

@@ -0,0 +1,167 @@
+;-*-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==30                             ;Set the size of the stack to 30 words.
+PDL:    BLOCK PDLLEN                   ;Reserve the stack memory
+
+CHTTYO==1                              ;Define a channel for TTY output.
+CHDSKI==2                              ;Read channel for disk input.
+
+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.
+FIELD:  BLOCK 9                        ;Reserve 9 words to store the grid. 
+
+START:  MOVE  P,[-PDLLEN,,PDL-1]       ;Initialize the stack.
+        .OPEN CHTTYO,[.UAO,,'TTY]      ;Open an output channel on the TTY.
+         .LOSE %LSFIL                  ;Gobble up any errors.
+        MOVE  A,[440700,,WELCOME]        ;Print the welcome message
+        PUSHJ P,PUTLN
+        PUSHJ P,GETJCL                 ;Read the command line.
+        MOVE  A,[440700,,LOADING]        ;Print the loading message
+        PUSHJ P,OUTSTR
+        MOVE  A,[440600,,FNAME1]        ;Load FNAME1 into the A
+        PUSHJ P,OUTSTR                  ;Print the name in a single line
+        MOVE  A,[440600,,FNAME2]        ;Now repeat with FNAME2
+        PUSHJ P,PUTLN
+        ; Load the files into field
+        MOVEI A,FIELD                  ;Store the address of field in C
+        PUSHJ P,IMPRTF                 ;Load the file
+        PUSHJ P,PFIELD                 ;Print the loaded field.
+
+         
+        JRST  DONE                     ;Jump to the end of the program.
+
+;Subroutine to read the JCL from DDT and get the command line parameters.
+GETJCL: PUSH  P,A                      ;Save the register A.
+        PUSH  P,B                      ;Save the register B.
+        SETZM JCL                      ;Zero out the JCL
+        MOVE  A,[JCL,,JCL+30]
+        BLT   A,JCL+30
+        .BREAK 12,[..RJCL,,JCL]        ;Request the JCL.
+        MOVE  A,[440700,,JCL]          ;Load the command parameters into A.
+        MOVE  B,[440600,,FNAME1]       ;Pointer to the first file name.
+        PUSHJ P,TOSIXB                 ;Transfer the first word into FNAME1
+        MOVE  B,[440600,,FNAME2]       ;Pointer to the second file name.
+        PUSHJ P,TOSIXB                 ;Transfer the second word into FNAME2
+        POP   P,B                      ;Restore the B register.
+        POP   P,A                      ;Restore the A register.
+        POPJ  P,                       ;Return from routine.
+
+;Subroutine to copy a string. Takes a bytepointer in A and B
+;where A is the source and B is the destination. It will stop copying, if
+;the end of the string is reached, or a whitespace is encounterd,
+CPSTR:  PUSH  P,D                      ;Store the contents of register D.
+CPSTLP: ILDB  D,A                      ;Load the next character from A.
+        JUMPE D,CPSTEN                 ;Exit the loop.
+        CAIN  D,40                     ;If the character is whitespace
+        JUMPA CPSTEN                   ;exit the loop.
+        IDPB  D,B                      ;Deposit the charcter at destination.
+        JRST  CPSTLP                   ;Repeat with the next character
+CPSTEN: POP   P,D                      ;Restore the D register.
+        POPJ  P,                       ;Return from function.
+
+;Subroutine to convert an ASCII string into SIXBIT. Takes a byte
+;pointer in A and B, where A is the source and B is the destination.
+TOSIXB: PUSH  P,D                     ;Store the contents of register D.
+TOSLP:  ILDB  D,A                     ;Load the next character from A.
+        JUMPE D,TOSEN                 ;Exit the loop, if charachter is null.
+        CAIN  D,40                    ;If the character is a whitespace,
+        JUMPA TOSEN                   ;exit the loop.
+        CAIL  D,140                   ;If the character is > 96,
+         SUBI D,40                    ;then cut it down, so it's in range.
+        SUBI  D,40                    ;Convert 32..95 to 0..63
+        IDPB  D,B                     ;Deposit the character in the destination.
+        JRST  TOSLP                   ;Repeat with next character.
+TOSEN:  POP   P,D                     ;Restore the D register.
+        POPJ  P,                      ;Return from function.
+
+;Subroutine to print a string of text on the output.
+;Clobbers A.
+OUTSTR: PUSH  P,B                      ;Save register B.
+OUT:    ILDB  B,A                      ;Load the next byte from A.
+        JUMPE B,OUTEX                  ;Exit the routine, if all bytes are done.
+        TLNN  A,000100                 ;Test, if the SIXBIT flag is set.
+         ADDI B,40                     ;Convert SIXBIT to ASCII.
+        .IOT  CHTTYO,B                 ;Print a character.
+        JRST  OUT                      ;Jump back to print the next character.
+OUTEX:  POP   P,B                      ;Restore B to its original value.
+        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.
+
+;Subroutine to that prints the entire play field.
+;The contents of the field is expected in FIELD
+PFIELD: PUSH  P,A                      ;Save the A register.
+        PUSH  P,B                      ;Save the contents of register B.
+        PUSH  P,X                      ;Save the contents of the index register.
+        PUSH  P,Y                      ;Save the contents of the Y register
+        MOVE  X,[440400,,FIELD]        ;Store a bytepointer in X.
+PFIELN: .IOT  CHTTYO,[^M]              ;Print a carriage return.
+        .IOT  CHTTYO,[^J]              ;Print a new line.
+        MOVE  A,[440700,,HLINE]          ;Print a horizontal line.
+        POPJ  P,PUTLN
+        MOVEI Y,011                    ;Load the index register with 9.
+        MOVEI B,174                    ;Print a '|' symbol.
+        .IOT  CHTTYO,B
+PFIENO: MOVEi B,020                    ;Print a space.
+        .IOT  CHTTYO,B
+        ILDB  B,X                      ;Load the next field.
+        JUMPE B,PFIEEX                 ;Exit, if no more elements are read.
+        ADDI  B,060                    ;Convert number into char.
+        .IOT  CHTTYO,B                 ;Print the number.
+        .IOT  CHTTYO,[ ]               ;Print a space.
+        .IOT  CHTTYO,[|]               ;Print the vertical line.
+        SOJE  Y,PFIELN                 ;End the line and start a new one.
+        JUMPA PFIENO                   ;Jump back to print the next number.
+
+PFIEEX: POP   P,Y                      ;Restore the Y register.
+        POP   P,X                      ;Restore the index register.
+        POP   P,B                      ;Restore the B register.
+        POP   P,A                      ;Restore the A register.
+        POPJ  P,                       ;Return from the subroutine.
+
+;Subroutine that reads the contents of the file into the buffer at FIELD
+IMPRTF: PUSH  P,A                      ;Save the A register.
+        PUSH  P,B                      ;Save the B register.
+        PUSH  P,X                      ;Save the index register.
+        MOVE  X,[440400,,FIELD]        ;Init a 4-bit byte pointer to FIELD.
+        .CALL [SETZ ? SIXBIT/OPEN/     ;Open a file descriptor.
+            [.UAI,,CHDSKI] ? [SIXBIT/DSK/] ;Mode, channel and device name
+            %CLIN,,FNAME1 ? 400000,,FNAME2]
+         .LOSE %LSFIL                  ;Handle errors after opening the file
+IMPRD:  .IOT  CHDSKI,A                 ;Read an ascii char into A.
+        JUMPL A,IMPREX                 ;If there was nothing read, exit.
+        CAIGE A,060                    ;Is A >= '0' then skip,
+        JUMPA IMPRD                    ;else read the next char.
+        CAILE A,071                    ;If A <= '9', then skip.
+        JUMPA IMPRD                    ;else, read the next char.
+        SUBI  A,060                    ;Convert A from the num char into int.
+        IDPB  A,X                      ;Store the byte and increment.
+        JUMPA IMPRD                    ;Jump back to read the next byte.
+IMPREX: .CALL [SETZ ? SIXBIT/CLOSE/    ;Close the file, before returning.
+                [,,CHDSKI] ((SETZ))]
+         .LOSE %LSFIL
+        POP   P,X                      ;Restore the X register.
+        POP   P,B                      ;Restore the B register
+        POP   P,A                      ;Restore the A register.
+        POPJ  P,                       ;Return from the input subroutine,
+DONE:   .LOGOUT  2,                    ;Exit point for the program.
+WELCOME:ASCIZ /SUDOKU SOLVER v0.1/     ;Text of the welcome banner.
+LOADING:ASCIZ /LOADING /               ;Load message.
+HLINE:  ASCIZ /|---|---|---|---|---|---|---|---|---|/ ;A horizontal line.
+END     START