	(INTERNAL-ARRAY)

	Syntax:    MH0 (header-word)
		   MH1 (header-word)
		   MH2 (header-word)
		   MH3 (header-word)

	MH0 through MH3 are internal-array verbs which return or set the
	value contained within elements of the header for internal
	Matrices (0) through (3).  You should reference the header values
	by header keyword names (see the documentation for Keywords for a 
	list of available keyword adverbs).

	If the verb appears to the left of an equal sign, than the
	specified header parameter has its value changed to the value
	of the expression to the right of the equal sign.

	If the verb appears in an expression or as an argument to a
	verb or procedure, then the value of the specified header
	parameter for that matrix is returned.

	If MH0 through MH3 is not to the left of an equal sign, and if
	the argument you supply MH0 through MH3 is a keyword adverb that
	refers to a real-valued header parameter, then MH0 through MH3
	will return a floating-point value.

	If MH0 through MH3 is not to the left of an equal sign, and if
	the argument you supply MH0 through MH3 is a keyword adverb that
	refers to a string header parameter, then MH0 through MH3 will
	return a string.

	If MH0 through MH3 is to the left of an equal sign, and if the
	argument you supply MH0 through MH3 is a keyword adverb that
	refers to a real-valued header parameter, then you should
	supply a real-valued expression to the right of the equal
	sign.

	If MH0 through MH3 is to the left of an equal sign, and if the
	argument you supply MH0 through MH3 is a keyword adverb that
	refers to a string header parameter, then you should supply a
	string expression to the right of the equal sign.

	No adverbs are used or set by MH0 through MH3.

	See the description of internal-array verbs for restrictions on
	their use.

	EXAMPLES:

	.  For real-valued header parameters:

		PRINT MH0(MNAXIS1)		

	   Will print the number of x-axis pixels in Matrix (0).

		X = MH3(MDELT2)  

	   Will assign to X the value of the increment between y-axis
	   pixels for Matrix (3).

		MH0(MRVAL1) = SQRT(MH3(MRVAL1)*MH2(MRVAL2))	
					
	   Changes the value of the x-axis reference coordinate in
	   Matrix (0) to the square root of the x-axis reference
	   coordinate in Matrix 3 times the value of the y-axis
	   reference coordinate in Matrix (2).

		X = MH3(MNAXIS1)*MH3(MNAXIS2)  

	   Assigns to X the value of the total number of cells in
	   Matrix (3).

	.  For string header parameters

		PRINT MH1(MDATE)   
	
	   Will print the date contained in the header of Matrix (1).
		
		XTITLE = CONCAT('Obj:',MH3(MOBJECT))

	   Will assign to XTITLE the concatenation of the string 'Obj:'
	   with the name of the observed object for the header of
	   Matrix (3).

		MH0(DATE) = '11/11/92' 

	   Changes the value of the date for the header in Matrix (0)
	   to the string '11/11/92'.
