wtvm_c( wid.i2.v, wrow.i4.v, wcol.i4.v, text.i1a.r, 
	 	nchars.i4.v, colors.i4.v )

	'wtvm_c' is a C callable (by value) windowed version of TVM.

	'wid' is the window ID of the window to read/write as returned by
	the WMAKE or 'wmake_c' routine.

	'wrow' and 'wcol' are the row and column within the window. The
	top left character inside the window border is row 1, column 1.

	The other arguments are the same as the corresopnding 'tvm_c'