sf_read_dac           Read DAC palette registers
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    procedure sf_read_dac prototype
      parameters byte array_buffer[ 0 ]

    The read/write DAC procedures allow the reading and writing of the
    DAC palette registers.  Enclosed on the Special Forces distribution
    disk are VGAGRAB.PRG and VGASHOW.PRG.  VGAGRAB is a memory resident
    320x200x256 image screen grabber, and VGASHOW is a utility which will
    redisplay the VGAGRAB'd image.  Their source code is a very good example
    of the DAC functions and the SF_MEM_READ()/WRITE() functions.

    It is important to remember that the byte array passed to the DAC
    functions should be exactly 771 elements long.  This is because the
    assembly code is hard coded to read all register entries.

    For example:

    vardef
      byte dac_array[ 771 ]
    enddef