Add punched tape emulation support

emulator.pas

@@ -2,7 +2,7 @@ program Emulator;
 
 {$MODE OBJFPC}
 
-uses Crt;
+uses SysUtils, Crt;
 
 const
     IO = $ffff;
@@ -14,7 +14,10 @@ var
     Addr, IP, RP: word; //Address argument and instruction and return pointers
     R: array [0 .. 3] of byte; //General-purpose registers
     Mem: array [0 .. $ffef] of byte; //Memory
-    Prog{$ifdef printer}, Prn{$endif}: file of byte; //Program file and printer
+    Prog{$ifdef printer}, Prn{$endif}{$ifdef tape}, TapeIn, TapeOut{$endif}: file of byte; //Program file, line printer, and punched tape reader and keypunch
+    {$ifdef tape}
+    TapePos: integer; //Punched tape reader position pointer
+    {$endif}
     Ch: ansichar; //Character for input and output
 
 begin
@@ -23,6 +26,9 @@ begin
     Hlt := false;
     IP := 0;
     RP := $fff0;
+    {$ifdef tape}
+    TapePos := 0;
+    {$endif}
 
     //Read a program file and check for errors
     if ParamCount <> 1 then begin
@@ -121,23 +127,42 @@ begin
         else if Op = 9 then R [X] := R [X] xor R [Y]
         //Load
         else if Op = $a then begin
-            //Input
+            //Dumb terminal input
             if Addr = IO then begin
                 Ch := ReadKey;
-                write (Ch);
+                write (Ch); //Local echo
                 R [X] := byte (Ch);
             end
+            //Punched tape reader
+            {$ifdef tape}
+            else if Addr = $fffd then begin
+                assign (TapeIn, 'tapein');
+                try
+                    reset (TapeIn);
+                    seek (TapeIn, TapePos);
+                    if eof (TapeIn) = false then begin
+                        read (TapeIn, R [X]);
+                        TapePos := TapePos + 1;
+                    end
+                    else R [X] := 0;
+                    close (TapeIn);
+                except
+                    R [X] := 0;
+                    TapePos := 0;
+                end;
+            end
+            {$endif}
             //Regular load
             else R [X] := Mem [Addr];
         end
         //Store
         else if Op = $b then begin
-            //Output
+            //Dumb terminal output
             if Addr = IO then begin
                 Ch := ansichar (R [X]);
                 write (Ch);
             end
-            //Printer
+            //Line printer
             {$ifdef printer}
             else if Addr = $fffe then begin
                 assign (Prn, '/dev/usb/lp0');
@@ -149,6 +174,29 @@ begin
                 end;
             end
             {$endif}
+            //Punched tape keypunch
+            {$ifdef tape}
+            else if Addr = $fffd then begin
+                assign (TapeOut, 'tapeout');
+                if FileExists ('tapeout') = false then begin
+                    try
+                        rewrite (TapeOut);
+                        write (TapeOut, R [X]);
+                        close (TapeOut);
+                    except
+                    end;
+                end
+                else begin
+                    try
+                        reset (TapeOut);
+                        seek (TapeOut, FileSize (TapeOut));
+                        write (TapeOut, R [X]);
+                        close (TapeOut);
+                    except
+                    end;
+                end;
+            end
+            {$endif}
             //Regular store
             else Mem [Addr] := R [X];
         end

readme.md

@@ -91,10 +91,14 @@ this.
 
 Arbitrary devices can be mapped to the other reserved addresses.
 
-The emulator can be compiled in Linux with support for a line printer at
+The emulator can be compiled with support for a line printer at
-/dev/usb/lp0 with the argument -dprinter. The printer is mapped to
+/dev/usb/lp0 with the argument -dprinter, and for an emulated punched
-address FFFE in the emulator. If you wish to use a different setup you
+tape reader and keypunch at tapein and tapeout respectively with -dtape.
-have to modify the code yourself.
+The printer is mapped to address FFFE in the emulator and the tape
+reader and keypunch to FFFD. To reset the tape reader to the beginning
+of a tape, for example to change the tape, read once with no file at
+tapein. If you wish to use a different setup you have to modify the code
+yourself.
 
 Initial Program Loader
 ----------------------