syntax:
	shift.exe options gear_file

Where the gear_file is an ASCII file containing pairs of lines of numbers.

The first line of a pair specifies the number of teeth on the ring gears.

The second line of a pair specifies the number of teeth on the cog gears.

Blank lines are ignored.

Lines that start with a '#' are considered comments.

Optional inputs are:

 c = nnn   Inputs crank arm length in mm (for Sheldon Brown's raitios).
           Default crank size is 170mm.

 w = sss   Inputs wheel size
           Default wheel size is 27 x 1 1/4

    Valid wheel sizes are:
	27 x 1 3/8
	27 x 1 1/4
	27 x 1 1/8
	27 x 1
	700 x 44
	700 x 38
	700 x 35
	700 x 32
	700 x 28
	700 x 25
	700 x 20
	26 x 2.125
	26 x 1.9
	26 x 1.5
	26 x 1.25
	26 x 1.0
	650c
	wide tubular
	tubular
	26 x 1 3/8
	24
	24 x 1
	20 x 1.75
	20 x 1 1/4
	17 x 1 1/4
	16 x 1 3/8

White space and case are ignored in the wheel size entry

 d = glsp  Controls the display.  Where:
           g = draw gear table
           l = draw log table
           s = draw Sheldons ratios
           p = draw shift pattern
           w = 132 column log table
 by default, all outputs are drawn.