Condensed Balance Sheets (Parenthetical) - USD ($)	Jan. 31, 2019	Apr. 30, 2018
Allowance for doubtful account receivable	$ 3,465	$ 6,651
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	3,542,171	3,534,784
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