Description of all scripts:

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extract.prl:

	Used to pull out stuff to give to students for PS1B

	Copies everyone's executable in a og/ directory
	Copies everyone's Inventor files in a gallery_ps1a/ directory
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grade.prl:

	Used to grade one students assignment.

	See web page for details.
	http://graphics.lcs.mit.edu/6.837/f96/internal_pages/grading.html
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progress.prl:

	Used to check the progess of grading, and make sure we haven't
	missed any students.

	Lists all students, if their project has been graded, and by which
	grader.
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verify.prl:

	Used to make a quick check of all projects before grading.

	Verifies the existence of each student's directory
	Verifies the existence of each student's source file 
	Verifies the existence of each student's executable 
	Verifies that 4 appropriately-named Inventor files exist
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rgb4to1.prl:

	Used to make transparencies for in-class exhibition.

	Replaces black in picture with white
	Adds grey border
	Tiles four pictures into one large picture
	Converts to PostScript
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