Condensed Balance Sheets (Parenthetical) - USD ($)	Jul. 31, 2017	Apr. 30, 2017
Allowance for doubtful account receivable	$ 2,425	$ 2,425
Convertible preferred stock, shares authorized	1,000,000	1,000,000
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	10,000,000	10,000,000
Common stock, shares issued	8,502,881	8,502,881
Common stock, shares outstanding	8,502,881	8,502,881
Treasury stock, shares	3,557,931	3,557,606
Series 1 Noncumulative Preferred Stock [Member]
Convertible preferred stock, shares authorized	25,000	25,000
Convertible preferred stock, stated value	$ 20	$ 20
Convertible preferred stock, shares issued	4,100	4,100
Convertible preferred stock, shares outstanding	4,100	4,100