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Minor Debugger improvements, notes, etc, while debugging the PDP-11 BASIC

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Jeff Parsons 2016-10-20 22:57:22 -07:00 • committed by Jeff Parsons
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apps/pdp11/tapes/basic/README.md
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@ -23,9 +23,9 @@ Third-party resources include:
Debugging Notes Debugging Notes
--------------- ---------------
One of the first things I noticed when debugging PDP-11 BASIC was its reliance on TRAP instructions. One of the first things I noticed when debugging PDP-11 BASIC was its heavy reliance on TRAP instructions.
For example, `TRAP 000` used to output the character in R2 to the terminal. Let's take a closer look at how its For example, `TRAP 000` is used to output the character in R2 to the terminal. Let's take a closer look at how
TRAP handler works. its TRAP handler works.
First, if you check the table of PDP-11 trap vectors, you'll see that the vector for TRAP instructions is 000034. First, if you check the table of PDP-11 trap vectors, you'll see that the vector for TRAP instructions is 000034.
So let's dump the contents of the two-word vector at 000034: So let's dump the contents of the two-word vector at 000034: