218 lines
6.4 KiB
Groff
218 lines
6.4 KiB
Groff
.Dd November 7, 1993
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.Dt SPKR 4
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.Os FreeBSD
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.Sh NAME
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.Nm spkr
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.Nd console speaker device driver
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.Sh SYNOPSIS
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.Cd pseudo-device speaker
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.Fd #include <machine/speaker.h>
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.Sh DESCRIPTION
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The speaker device driver allows applications to control the PC console
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speaker on an
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.Tn IBM-PC Ns --compatible
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machine running FreeBSD.
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.Pp
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Only one process may have this device open at any given time;
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.Xr open 2
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and
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.Xr close 2
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are used to lock and relinquish it. An attempt to open when
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another process has the device locked will return -1 with an
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.Er EBUSY
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error
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indication. Writes to the device are interpreted as `play strings' in a
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simple ASCII melody notation. An
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.Xr ioctl 2
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request
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for tone generation at arbitrary
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frequencies is also supported.
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.Pp
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Sound-generation does not monopolize the processor; in fact, the driver
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spends most of its time sleeping while the PC hardware is emitting
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tones. Other processes may emit beeps while the driver is running.
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.Pp
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Applications may call
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.Xr ioctl 2
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on a speaker file descriptor to control the
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speaker driver directly; definitions for the
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.Xr ioctl 2
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interface are in
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.Pa /usr/include/machine/speaker.h .
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The
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.Li tone_t
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structure used in these calls has two fields,
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specifying a frequency (in Hz) and a duration (in 1/100ths of a second).
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A frequency of zero is interpreted as a rest.
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.Pp
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At present there are two such
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.Xr ioctl 2
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calls.
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.Dv SPKRTONE
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accepts a pointer to a
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single tone structure as third argument and plays it.
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.Dv SPKRTUNE
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accepts a
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pointer to the first of an array of tone structures and plays them in
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continuous sequence; this array must be terminated by a final member with
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a zero duration.
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.Pp
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The play-string language is modelled on the PLAY statement conventions of
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.Tn IBM
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Advanced BASIC 2.0. The
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.Li MB ,
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.Li MF ,
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and
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.Li X
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primitives of PLAY are not
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useful in a timesharing environment and are omitted. The `octave-tracking'
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feature and the slur mark are new.
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.Pp
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There are 84 accessible notes numbered 1-83 in 7 octaves, each running from
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C to B, numbered 0-6; the scale is equal-tempered A440 and octave 3 starts
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with middle C. By default, the play function emits half-second notes with the
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last 1/16th second being `rest time'.
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.Pp
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Play strings are interpreted left to right as a series of play command groups;
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letter case is ignored. Play command groups are as follows:
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.Bl -tag -width CDEFGABxx
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.It Li CDEFGAB
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Letters A through G cause the corresponding note to be played in the
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current octave. A note letter may optionally be followed by an
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.Dq Em "accidental sign" ,
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one of # + or -; the first two of these cause it to be sharped one
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half-tone, the last causes it to be flatted one half-tone. It may
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also be followed by a time value number and by sustain dots (see
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below). Time values are interpreted as for the L command below.
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.It Ns Li O Sy n
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If
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.Sy n
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is numeric, this sets the current octave.
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.Sy n
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may also be one of
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.Li L
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or
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.Li N
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to enable or disable octave-tracking (it is disabled by default).
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When octave-tracking is on, interpretation of a pair of letter notes
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will change octaves if necessary in order to make the smallest
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possible jump between notes. Thus ``olbc'' will be played as
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``olb>c'', and ``olcb'' as ``olc<b''. Octave locking is disabled for
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one letter note following >, < and O[0123456]. (The octave-locking
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feature is not supported in
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.Tn IBM
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BASIC.)
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.It Li >
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Bump the current octave up one.
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.It Li <
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Drop the current octave down one.
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.It Ns Li N Sy n
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Play note
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.Sy n ,
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.Sy n
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being 1 to 84 or 0 for a rest of current time value.
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May be followed by sustain dots.
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.It Ns Li L Sy n
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Sets the current time value for notes. The default is
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.Li L4 ,
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quarter or crotchet notes. The lowest possible value is 1; values up
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to 64 are accepted.
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.Li L1
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sets whole notes,
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.Li L2
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sets half notes,
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.Li L4
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sets quarter notes, etc.
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.It Ns Li P Sy n
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Pause (rest), with
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.Sy n
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interpreted as for
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.Ns Li L Sy n .
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May be followed by
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sustain dots. May also be written
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.Li ~ .
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.It Ns Li T Sy n
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Sets the number of quarter notes per minute; default is 120. Musical
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names for common tempi are:
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.Bd -literal -offset indent
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Tempo Beats Per Minute
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very slow Larghissimo
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Largo 40-60
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Larghetto 60-66
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Grave
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Lento
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Adagio 66-76
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slow Adagietto
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Andante 76-108
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medium Andantino
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Moderato 108-120
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fast Allegretto
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Allegro 120-168
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Vivace
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Veloce
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Presto 168-208
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very fast Prestissimo
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.Ed
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.It Li M[LNS]
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Set articulation.
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.Li MN
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.Ns No ( Li N
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for normal) is the default; the last 1/8th of
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the note's value is rest time. You can set
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.Li ML
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for legato (no rest space) or
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.Li MS
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for staccato (1/4 rest space).
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.El
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.Pp
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Notes (that is,
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.Li CDEFGAB
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or
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.Li N
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command character groups) may be followed by
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sustain dots. Each dot causes the note's value to be lengthened by one-half
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for each one. Thus, a note dotted once is held for 3/2 of its undotted value;
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dotted twice, it is held 9/4, and three times would give 27/8.
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.Pp
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A note and its sustain dots may also be followed by a slur mark (underscore).
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This causes the normal micro-rest after the note to be filled in, slurring it
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to the next one. (The slur feature is not supported in
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.Tn IBM
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BASIC.)
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.Pp
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Whitespace in play strings is simply skipped and may be used to separate
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melody sections.
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.Sh BUGS
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Due to roundoff in the pitch tables and slop in the tone-generation and timer
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hardware (neither of which was designed for precision), neither pitch accuracy
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nor timings will be mathematically exact. There is no volume control.
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.Pp
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The action of two or more sustain dots does not reflect standard musical
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notation, in which each dot adds half the value of the previous dot
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modifier, not half the value of the note as modified. Thus, a note dotted
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once is held for 3/2 of its undotted value; dotted twice, it is held 7/4,
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and three times would give 15/8. The multiply-by-3/2 interpretation,
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however, is specified in the
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.Tn IBM
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BASIC manual and has been retained for
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compatibility.
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.Pp
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In play strings which are very long (longer than your system's physical I/O
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blocks) note suffixes or numbers may occasionally be parsed incorrectly due
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to crossing a block boundary.
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.Sh FILES
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.Bl -tag -width /dev/speakerxx
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.It Pa /dev/speaker
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speaker device file
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.El
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.Sh AUTHOR
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Eric S. Raymond <esr@snark.thyrsus.com) June 1990
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.Sh "PORTED BY"
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Andrew A. Chernov <ache@astral.msk.su>
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.Sh HISTORY
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The
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.Nm
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device appeared in
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.Fx 1.0 .
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