Add the ability to turn the local echo on or off in the emulator, make the rest of the included programs exit with a non-zero exit code on error, and fix and reword the readme slightly

disassembler.pas

@@ -36,7 +36,7 @@ begin
     //Read a program file and check for errors
     if ParamCount <> 1 then begin
         writeln ('Usage: disassembler program (> output)');
-        halt;
+        halt (1);
     end;
     {$i-}
     assign (Prog, ParamStr (1));
@@ -44,7 +44,7 @@ begin
     {$i+}
     if IOResult <> 0 then begin
         writeln ('Error: program file cannot be read from');
-        halt;
+        halt (1);
     end;
     repeat
         read (Prog, Bin [BP]);
@@ -52,7 +52,7 @@ begin
     until (eof (Prog)) or (BP = $fff0);
     if BP = $fff0 then begin
         writeln ('Error: memory overflow');
-        halt;
+        halt (1);
     end;
     //Save the end point and reinitialise the byte pointer
     EP := BP;

emulator.pas

@@ -31,7 +31,7 @@ const
     {$endif}
 
 var
-    Hlt, Verbose: boolean; //Halt, ASCII, and verbose flags
+    Hlt, Verbose, Echo: boolean; //Halt, verbose, and echo flags
     Op, Regs: 0 .. $f; //Opcode
     X, Y: 0 .. 3; //Register arguments
     Addr, IP, RP: word; //Immediate or address argument and instruction and return pointers
@@ -106,7 +106,7 @@ begin
             end;
         end;
         //Process the keypress
-        Output; //Local echo
+        if Echo then Output; //Local echo
         B := byte (Ch);
     end
     //Tape reader
@@ -166,6 +166,8 @@ begin
         {$endif}
         Ch := ansichar (B);
         Output;
+        if Ch = ansichar ($12) then Echo := true;
+        if Ch = ansichar ($14) then Echo := false;
     end
     //Printer
     {$ifdef printer}
@@ -260,8 +262,9 @@ end;
 
 begin
 
-    //Initialise the halt flag, the pointers, and the instruction counter
+    //Initialise the halt and echo flags, the pointers, and the instruction counter
     Hlt := false;
+    Echo := true;
     IP := 0;
     RP := LastRAM + 1;
     IC := 0;
@@ -279,20 +282,20 @@ begin
     //Check the arguments
     if ParamCount = 0 then begin
         writeln ('Usage: emulator (-v) program (2> verbose_output)');
-        halt;
+        halt (1);
     end;
     if ParamStr (1) = '-v' then begin
         Verbose := true;
         if ParamCount <> 2 then begin
             writeln ('Usage: emulator (-v) program (2> verbose_output)');
-            halt;
+            halt (1);
         end;
     end
     else begin
         Verbose := false;
         if ParamCount <> 1 then begin
             writeln ('Usage: emulator (-v) program (2> verbose_output)');
-            halt;
+            halt (1);
         end;
     end;
 
@@ -303,12 +306,12 @@ begin
     reset (Prog);
     if FileSize (Prog) > LastRAM + 1 then begin
         writeln ('Error: program size cannot exceed ', LastRam + 1, ' bytes');
-        halt;
+        halt (1);
     end;
     {$i+}
     if IOResult <> 0 then begin
         writeln ('Error: program file cannot be read from');
-        halt;
+        halt (1);
     end;
     repeat
         read (Prog, Mem [IP]);

readme.md

@@ -12,7 +12,7 @@ The repository includes an emulator implementation of Thingamajig with a
 control program for the emulated punched tape reader and punch, and an
 assembler and a disassembler, all written in FreePascal. It also
 includes couple of simple example programs for Thingamajig written in
-Assembly.
+assembly.
 
 Registers and Memory
 --------------------
@@ -70,8 +70,8 @@ comment elements are all optional, as is spacing between the arguments.
 For the arguments of each instruction see the previous section.
 
 Address arguments can be either absolute addresses or references to or
-relative to a label. Relative references are of the form LABEL +/- N,
-the spacing being optional.
+relative to a label. Relative references are of the form LABEL +/- N;
+the spacing is optional.
 
 In addition to the true instructions there are three
 pseudo-instructions. ORG defines the starting address of the program: it
@@ -93,17 +93,19 @@ Emulator
 --------
 
 By default the emulator runs at roughly 500 KIPS, has 2 KiB of RAM, and
-interacts with memory mapped devices at roughly 1000 CPS. The arguments
+interacts with memory mapped devices at roughly 1000 B/s. The arguments
 -dRAM4, -dRAM8, -dRAM16, -dRAM32, and -dRAM64 can be used to compile
 the emulator with 4, 8, 16, 32, or 64 KiB (minus the reserved addresses)
 of RAM respectively instead and the speed limitations can be removed
 with the argument -dfast.
 
 Input and output are handled by an emulated glass teletype terminal with
-local echo. Of the control characters only bell, backspace, line feed,
-and carriage return are used by the terminal. The backspace and delete
-characters are tied to their respective keys, and non-character keys
-input null.
+local echo on by default. Of the control characters bell, backspace,
+line feed, carriage return, and device control characters two and four
+are used by the terminal: the device control characters are used to turn
+the local echo on or off respectively, while the rest have their
+standard uses. The backspace and delete keys input their respective
+characters and non-character keys null.
 
 In Linux the emulator can be compiled with support for a character
 printer and an emulated punched tape reader and punch with the arguments

tapectl.pas

@@ -22,7 +22,7 @@ begin
     //Check whether to set the reader, the punch, or both
     if ParamCount <> 1 then begin
         writeln ('Usage: tapectl reader/punch/both');
-        halt;
+        halt (1);
     end;
     if ParamStr (1) = 'reader' then begin
         DoRead := true;
@@ -38,7 +38,7 @@ begin
     end
     else begin
         writeln ('Usage: tapectl reader/punch/both');
-        halt;
+        halt (1);
     end;
 
     //Assign the state file