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jvs:cigal:manual:chapter4:dflags

CIGAL Reference Manual, Chapter 4 (Variables): dflags

Dflags -- Integer variable controlling disk I/O options

usage: dflags = value

DFLAGS is an internally defined integer variable controlling options related to reading and writing disk files. The value of the DFLAGS parameter can be changed at any time and remains set until it is explicitly modified again. The meaning of the various flag bits are:

  Value (octal)    Meaning
    1       1o     Compress data when writing -- Runcode compression
    2       2o     Compress data when writing -- Packbits compression
    4       4o     Compress data when writing -- LZW compression
    8      10o     Use TIFF format when writing -- standard header (default)
   16      20o     Use TIFF format when writing -- short header
   32      40o     Use TIFF format when writing -- reverse byte order
   64     100o     Don't read/write header record
  512    1000o     Don't advance disks on read error (see [DISKHI][4])
 1024    2000o     Do advance disk on write error
 2048    4000o     Do advance disk on delete error
 4096   10000o     Change DATADIR to new disk on read jump
 8192   20000o     Change DATADIR to new disk on write jump
16384   40000o     When writing SOLID, store as multiple 2-D matrices

Notes:

1. By default CIGAL uses the TIFF (Tagged Image File Format, Aldus Corp.) format when writing binary data files (DFLAGS = 10o). For most CIGAL data variables this results in a standard TIFF file, readable by any software that recognizes the TIFF format (for exceptions see Note 3). Setting bit 20o lets you specify that an abbreviated, fixed length TIFF header should be used. Fixed length headers are generally easier to transfer to non-TIFF applications. The TIFF flags do not affect file reading; CIGAL automatically recognizes which file format is being used when reading input. See TIFF(1) for more on CIGAL's data file formats.

2. Bit values 512 to 8192 are used on systems with multiple disk drives to allow CIGAL to automatically make use of the extra disk space provided by multiple disks. These flags are used in conjunction with the variables DATADIR, DISKHI and DISKLO. See help for DISKHI(4) for more information about how to specify which disks are available for data files.

3. Graphics files containing vector data (such as created by the SKETCH command) are written in the TIFF format but are not likely to make sense to any other software because CIGAL vectors are not a standard TIFF format. Similarly, variables containing REAL (non-integer) data can be read but will probably not make sense to other software that uses the TIFF format. Because TIFF does not recognize 3-dimensional data formats, a SOLID variable written by CIGAL will be interpreted as a 2-dimensional matrix by other TIFF readers; this can be partially avoided by setting the 40000o bit in DFLAGS which causes solid variables to be written as a succesion of 2-d matrices. See TIFF(1) for more details of CIGAL's nonstandard TIFF usage.

4. [obsolete] Flag bit 10o is used when transferring data between a file and the graphics display screen (@0) in 16 color VGA mode. Data transfer is much faster if different bitplanes are written separately, compared to writing pixel by pixel. However, separating bitplanes means the data file will only make sense if it is read back to the same type of graphics display device. Usually you can avoid using this flag by selecting which of the different screen display identifiers to use because each name is associated with a different data format (see VGA(1) and READ(2)):

        @0      4 bit pixels in interleaved bitplanes
       @@0      8 bit bitplanes separated as 4 layers
        @1      8 bit file pixels converted to/from 4 bit screen pixels

See Also:
DISKHI(4), READ(2), TIFF(1), VGA(1)

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jvs/cigal/manual/chapter4/dflags.txt · Last modified: 2022/11/18 16:08 (external edit)