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Diffstat (limited to 'doc/mdk_tut.texi')
| -rw-r--r-- | doc/mdk_tut.texi | 19 |
1 files changed, 11 insertions, 8 deletions
diff --git a/doc/mdk_tut.texi b/doc/mdk_tut.texi index e2d3a15..9ff6f86 100644 --- a/doc/mdk_tut.texi +++ b/doc/mdk_tut.texi @@ -684,14 +684,17 @@ OPCODE = 34, MOD = I/O unit. @noindent In all the above instructions, the @samp{MOD} subfile must be in the range 0-20, since it denotes the operation's target device. The -@samp{IOC} instruction only makes sense for tape devices (@samp{MOD} = -0-7 or 20): it shifts the read/write pointer by the number of words -given by @samp{M} (if it equals zero, the tape is rewound)@footnote{In -Knuth's original definition, there are other control operations -available, but they do not make sense when implementing the block -devices as disk files (as we do in @sc{mdk} simulator). For the same -reason, @sc{mdk} devices are always ready, since all input-output -operations are performed using synchronous system calls.}. +@samp{IOC} instruction makes sense for magnetic tape devices (@samp{MOD} = +0-7): it shifts the read/write pointer by the number of blocks +given by @samp{M} (if it equals zero, the tape is rewound), paper tape +devices (@samp{MOD} = 20): @samp{M} should be 0, the tape is rewound, +and disk/drum devices (@samp{MOD} = 8-15): it moves the read/write +pointer to the block specified in rX and @samp{M} should be 0@footnote{In +Knuth's original definition, there are other control operations available, +but they do not make sense when implementing the devices as disk files (as +we do in @sc{mdk} simulator). For the same reason, @sc{mdk} devices are +always ready, since all input-output operations are performed using +synchronous system calls.}. @node Conversion operators, Shift operators, Input-output operators, MIX instruction set |