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Diffstat (limited to 'doc/mdk.texi')
| -rw-r--r-- | doc/mdk.texi | 58 |
1 files changed, 30 insertions, 28 deletions
diff --git a/doc/mdk.texi b/doc/mdk.texi index d481ae4..5f7941e 100644 --- a/doc/mdk.texi +++ b/doc/mdk.texi @@ -283,11 +283,12 @@ significant one. The sign is denoted by index 0. Graphically, Sample MIX words are @samp{- 12 00 11 01 63} and @samp{+ 12 11 34 43 00}. -You can refer to subfields within a word using a -@dfn{field specification} or @dfn{fspec} of the form @samp{(L:R)}, where -@samp{L} denotes the first byte and @samp{R} the last byte of the -subfield. When @samp{L} is zero, the subfield includes the word's -sign. An fspec can also be represented as a single value @samp{F}, given +You can refer to subfields within a word using a @dfn{field +specification} or @dfn{fspec} of the form ``(@var{l}:@var{r})'', where +@var{l} denotes the first byte, and @var{r} the last byte of the +subfield. +When @var{l} is zero, the subfield includes the word's +sign. An fspec can also be represented as a single value @code{F}, given by @code{F = 8*L + R} (thus the fspec @samp{(1:3)}, denoting the first three bytes of a word, is represented by the integer 11). @@ -303,17 +304,17 @@ address a memory cell) and the following registers: @cindex rIn @cindex register -@table @samp -@item rA +@table @asis +@item @code{rA} A register. General purpose register holding a word. Usually its contents serves as the operand of arithmetic and storing instructions. -@item rX +@item @code{rX} X register. General purpose register holding a word. Often it acts as an extension or a replacement of @samp{rA}. -@item rJ +@item @code{rJ} J (jump) register. This register stores positive two-byte values, usually representing a jump address. -@item rI[1-6] +@item @code{rI1}, @code{rI2}, @code{rI3}, @code{rI4}, @code{rI5}, @code{rI6} Index registers. These six registers can store a signed two-byte value. Their contents is used as indexing values for the computation of effective memory addresses. @@ -321,7 +322,7 @@ effective memory addresses. @cindex @sc{ov} @cindex @sc{cm} -@cindex @samp{Un} +@cindex @code{un} @cindex overflow toggle @cindex comparison indicator @cindex input-output devices @@ -338,23 +339,24 @@ A @dfn{comparison indicator} (having three values: @dfn{EQUAL}, @sc{cm}, and its possible values are abbreviated as @dfn{E}, @dfn{G} and @dfn{L}. @item -Input-output block devices. Each device is labelled as @samp{Un}, where -@samp{n} runs from 0 to 20. In Knuth's definition, @samp{U0-7} are -magnetic tape units, @samp{U8-15} are disks and drums, @samp{U16} is a -card reader, @samp{U17} is a card writer, @samp{U18} is a line printer -and, @samp{U19} is a typewriter terminal, and @samp{U20}, a paper -tape. Our implementation maps these devices to disk files, except for -@samp{U19}, which represents the standard output. +Input-output block devices. Each device is labelled as @code{un}, where +@code{n} runs from 0 to 20. In Knuth's definition, @code{u0} through +@code{u7} are magnetic tape units, @code{u8} through @code{15} are disks +and drums, @code{u16} is a card reader, @code{u17} is a card writer, +@code{u18} is +a line printer and, @code{u19} is a typewriter terminal, and @code{u20}, +a paper tape. Our implementation maps these devices to disk files, +except for @code{u19}, which represents the standard output. @end itemize -As noted above, communication of the MIX computer with the external -world is achieved by a set of input-output devices which can be -"connected" to it. Interchange of information is done in blocks of words -whose length depend on the device at hand (see @pxref{Devices}). These -words are interpreted by the device either as binary information (for -devices 0-16), or as representing printable characters (devices -17-20). In the last case, each MIX byte is mapped onto a character -according to the following table: +As noted above, the MIX computer communicates with the external world by +a set of input-output devices which can be ``connected'' to it. The +computer interchanges information using blocks of words whose length +depends on the device at hand (@pxref{Devices}). These words are +interpreted by the device either as binary information (for devices +0-16), or as representing printable characters (devices 17-20). In the +last case, each MIX byte is mapped onto a character according to the +following table: @multitable {00} {C} {00} {C} {00} {C} {00} {C} @item 00 @tab @tab 01 @tab A @tab 02 @tab B @tab 03 @tab C @@ -374,8 +376,8 @@ according to the following table: @end multitable @noindent The value 0 represents a whitespace. Lowercase letters (d, s, p) -correspond to symbols non representable as ASCII characters (uppercase -delta, sigma and gamma, respectively) and byte values 56-63 have no +correspond to symbols not representable as ASCII characters (uppercase +delta, sigma and gamma, respectively), and byte values 56-63 have no associated character. Finally, the MIX computer features a virtual CPU which controls the |