Condensing Sub-Code Bits

A program word will consist of instruction words and operand words.  The instruction word will consist of the instruction code and sub-codes.  The sub-codes will generally only be used to recreate the original program and will not be used during execution (though there will be a few exceptions).  The code will reside in the lower 10 bits of the instruction word, which will allow for 1,024 different codes (which should be sufficient).  This leaves the upper 6 bits for the sub-codes.

There are already five sub-codes that need to be stored in the instruction word, including the Parentheses, Colon, LET, Keep and Question sub-codes.  This only leaves one bit for another sub-code and there are a lot more commands to implement.  The sub-code bit usage needed to be reduced.  As it so happens, the LET, Keep and Question sub-codes will never be on the same code, so only one bit is really required for these sub-codes.

To accomplish this, these three sub-codes were replaced with the new Option sub-code.  The LET and INPUT translate routines now set this sub-code instead of the individual sub-codes that were removed.  This new sub-code also can be reused for other commands requiring an individual sub-code.

The bits of the sub-codes were also rearranged with the sub-codes that will be used in the instruction words (Parentheses, Colon, and Option) in the same bit positions.  This will prevent having two sets of sub-code definitions.  A new Program Mask sub-code definition was added that will be used the mask the program sub-codes from the other token sub-codes when the instruction is created.

So that the proper sub-code can be output during testing, an option name variable was added to the table entries.  Commands used the option sub-code will have the text name of the sub-code in the option name.  In the token text routine, if a token has the Option sub-code, the option name is output (or the string "BUG" if the code does not have an option name).

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