Added the ^L MACRO-10 unary zero-bit-counting operator, and updated the last blog post with expression parser differences (eg, interpretation of numbers with a decimal point)
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Jeff
Jeff Parsons
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1 changed files with 41 additions and 13 deletions
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@ -21,7 +21,7 @@ falls into these categories:
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Floating-point is the biggest chunk of work, which I'm going to save for last, with the hope that most PDP-10 software
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didn't use floating-point. However, if all PDP-10 systems included floating-point hardware (which I haven't been able to
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confirm yet), I may have no choice. Floating-point emulation in JavaScript isn't hard -- PCjs already includes an
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confirm yet), I may have no choice. Floating-point emulation in JavaScript isn't hard -- PCjs already includes
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[8087 Coprocessor Emulation](/modules/pcx86/lib/x86fpu.js) -- but getting all the details right is time-consuming.
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The PDP-10 has a lot of instructions, and I quickly had far more instructions than I was willing or able to write tests for.
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@ -57,10 +57,10 @@ The Debugger invokes the MACRO-10 mini-assembler whenever the argument following
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As previously described in the section on [PDPjs PDP-10 Opcode Tests](/apps/pdp10/tests/opcodes/), the Debugger already
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allowed you to assemble instructions directly into memory (eg, `a 100 hrli 1,111111`). This "immediate mode" feature is provided
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exclusively by the Debugger; MACRO-10 mini-assembler features are not available in that mode.
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exclusively by the Debugger; MACRO-10 features are not available in that mode.
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However, one feature that *is* available in both the Debugger and the mini-assembler is full MACRO-10-style expression evaluation,
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since they share the same expression parser. Here are some examples, using the Debugger's 'print' command:
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since they share the same expression parser. Here are some examples, using the Debugger's "print" command:
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>> print 27
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23. 0o000027
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@ -100,10 +100,26 @@ so:
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>> print 5K
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0o000000005000 2560.
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>> print 5M
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0o000005000000 1310720.
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>> print 5G
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0o005000000000 671088640.
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>> print ^D5K
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0o000000011610 5000.
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>> print ^D5M
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0o000023045500 5000000.
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>> print ^D5G
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0o045201371000 5000000000.
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Binary shifting using a B suffix is also supported:
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Binary shifting using a **B** suffix is also supported. Note that MACRO-10 binary shifting is a "bit" unusual by today's
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standards, because the value after the **B**, *n*, is not a count but rather the desired bit position of the right-most bit of
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the original value. Moreover, MACRO-10 considers bit 0 the left-most bit, and bit 35 the right-most bit. Last but not least,
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*n* is always interpreted as a decimal value, regardless of the current base (radix). *n* can be converted to a shift count
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by calculating (35 - n): if the count is positive, it's a left-shift, and if it's negative, it's a right-shift.
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>> print 1B0
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0o400000000000 -34359738368.
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@ -123,8 +139,8 @@ Binary shifting using a B suffix is also supported:
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>> print -1B70
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0o000000000001 1.
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And as the MACRO-10 ASSEMBLER PROGRAMMER'S REFERENCE MANUAL (June 1972), p. 1-17, points out, all the following expressions are
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equivalent:
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And as the [MACRO-10 Assembler Programmer's Reference Manual (June 1972)](http://archive.pcjs.org/pubs/dec/pdp10/tops10/Macro_Assembler_Reference_Manual-Jun72.pdf),
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p. 1-17, points out, all the following expressions are equivalent:
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>> print 10B32
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0o000000000100 64. '@'
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@ -142,7 +158,8 @@ equivalent:
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0o000000000100 64. '@'
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"Left arrow" shifting is also supported, although the character that the original MACRO-10 manuals referred to as a "left arrow"
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is actually an underscore; later manuals refer to this as "underscore shifting":
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is actually an underscore; later manuals refer to this as "underscore shifting". Underscore shifting uses straightforward shift
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counts: if the count is positive, it's a left-shift, and if it's negative, it's a right-shift.
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>> print 1_^D18
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0o000001000000 262144.
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@ -150,8 +167,12 @@ is actually an underscore; later manuals refer to this as "underscore shifting":
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>> print -1_^D-18
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0o000000777777 262143.
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Character-based constants are also supported, in the both 7-bit ASCII the 6-bit SIXBIT formats. Use double-quotes
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for 7-bit right-justified character constants and single-quotes for 6-bit right-justified character constants:
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Character constants are also supported, in both the 7-bit ASCII and 6-bit SIXBIT formats. If more than 5 7-bit characters
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or more than 6 6-bit characters are specified, an error will be reported, since the value cannot fit in a 36-bit word. The
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character values will be stored in the same order that they are listed, but unlike values generated by MACRO-10 pseudo-ops
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**ASCII**, **ASCIZ**, and **SIXBIT**, the final value will be right-justified instead of left-justified.
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Use double-quotes for ASCII constants and single-quotes for SIXBIT constants:
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>> print +'SIXBIT'
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0o635170425164 -13255955852.
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@ -159,20 +180,27 @@ for 7-bit right-justified character constants and single-quotes for 6-bit right-
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>> print +"HELLO"
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0o221054623117 19473311311.
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NOTE: When using the PCjs debugger, the constant must be preceded by an arithmetic operator, otherwise it interprets the
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quoted argument as a string. This is an idiosyncrasy of the "print" command, not the expression parser.
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NOTE: When using the PCjs debugger, the constant must be preceded by an arithmetic operator (eg, '+'), otherwise it interprets
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the quoted argument as a string. This is an idiosyncrasy of the "print" command, not the expression parser.
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All MACRO-10 logical and arithmetic operators are supported, including:
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Most MACRO-10 logical and arithmetic operators are supported, including:
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- Unary arithmetic operators (+ and -)
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- Unary complement operator (^-, aliased to ~)
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- Unary base overrides (^D, ^O, and ^B)
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- Unary zero-bit-count operator (^L)
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- Binary shifting (B) and underscore shifting (_) operators
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- Logical binary operations (! for OR, ^! for XOR, and & for AND)
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- Multiplication and division (* and /)
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- Addition and subtraction (+ and -)
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- Angle brackets for expression grouping (< and >)
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Unfortunately, since the PCjs expression parser predates MACRO-10 support, there are bound to be differences that I
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haven't ironed out yet. One known difference involves numeric constants with a trailing period (decimal point): PCjs
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historically treats such constants as decimal *integers*, whereas MACRO-10 treats numeric constants with either a
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leading, embedded, or trailing period as a decimal *floating-point* number. I've chosen to ignore this difference for
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now, since I'm holding off on all floating-point support for as long as possible.
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Much more work is needed to make the MACRO-10 "Mini-Assembler" a general-purpose assembler, but it's already proved itself
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useful in assembling the following tests:
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