Interrupt system implemented, some new programs.

Programs/testPrograms/dispatchTest.asm

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+; Tests BRD, the only branch whose destination is not written into the program.
+;
+; A table of addresses in the Data Segment is walked with one Data Pointer, each
+; entry is pulled out with LDD, and BRD jumps to it. That is dispatch: choosing
+; where to go from data rather than from a branch the assembler laid down.
+;
+; Correct output is:
+;   one
+;   two
+;   three
+;   done
+
+#Program
+
+start:
+  SETD.0 Handlers   ; DP0 walks the table of handler addresses.
+  INIB 0d3          ; Three of them.
+
+dispatchLoop:
+  LDD.1.0           ; DP1 becomes the address of the next handler.
+  BRD.1             ; Go there. The handler branches back to itself.
+
+; Each handler prints its name and returns to the loop by hand. There is no CALL
+; here on purpose, so that what BRD does is the only thing under test.
+handlerOne:
+  SETD.2 One
+  CALL printDP2
+  BRI nextHandler
+
+handlerTwo:
+  SETD.2 Two
+  CALL printDP2
+  BRI nextHandler
+
+handlerThree:
+  SETD.2 Three
+  CALL printDP2
+  BRI nextHandler
+
+nextHandler:
+  DPUP.0 0d02       ; Step over the two byte table entry.
+  DECB
+  BRB finished
+  BRI dispatchLoop
+
+finished:
+  SETD.2 Done
+  CALL printDP2
+  HALT
+
+printDP2:
+  LDA.2
+  BRA printDone
+  OUTA 0x00
+  INCD.2
+  BRI printDP2
+ printDone:
+  INIA 0x0A
+  OUTA 0x00
+  RET
+
+#Data
+
+One:
+"one"
+Two:
+"two"
+Three:
+"three"
+Done:
+"done"
+
+; The dispatch table. Each name becomes the address of that handler.
+Handlers:
+handlerOne
+handlerTwo
+handlerThree