NAME
	  glIndexMask -	control	the writing of individual bits in the
	  color	index buffers


     C SPECIFICATION
	  void glIndexMask( GLuint mask	)


     PARAMETERS
	  mask	Specifies a bit	mask to	enable and disable the writing
		of individual bits in the color	index buffers.
		Initially, the mask is all 1's.

     DESCRIPTION
	  glIndexMask controls the writing of individual bits in the
	  color	index buffers.	The least significant n	bits of	mask,
	  where	n is the number	of bits	in a color index buffer,
	  specify a mask.  Where a 1 (one) appears in the mask,	it's
	  possible to write to the corresponding bit in	the color
	  index	buffer (or buffers). Where a 0 (zero) appears, the
	  corresponding	bit is write-protected.

	  This mask is used only in color index	mode, and it affects
	  only the buffers currently selected for writing (see
	  glDrawBuffer).  Initially, all bits are enabled for writing.

     ERRORS
	  GL_INVALID_OPERATION is generated if glIndexMask is executed
	  between the execution	of glBegin and the corresponding
	  execution of glEnd.

     ASSOCIATED	GETS
	  glGet	with argument GL_INDEX_WRITEMASK

     SEE ALSO
	  glColorMask, glDepthMask, glDrawBuffer, glIndex,
	  glIndexPointer, glStencilMask