Reconciliation of Numerators and Denominators of Basic and Diluted Earnings Per Share Computations (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2019	Jan. 31, 2018
Basic and Diluted:
Net income from continuing operations	$ 42,881	$ 21,895	$ 473,394	$ 721,057
Net (loss) income from discontinued operations	(163,594)	171,432	(106,862)	235,248
Net (loss) income	$ (120,713)	$ 193,327	$ 366,532	$ 956,305
Denominator:
Basic weighted average number of common shares outstanding	17,485,106	16,829,581	17,060,903	17,029,822
Dilutive effect of common stock options	368,727	378,560	354,095	364,870
Diluted weighted average number of common shares outstanding	17,853,833	17,208,141	17,414,998	17,394,692
Per share information:
Income from continuing operations per common share - basic and diluted	$ 0	$ 0	$ 0.03	$ 0.04
(Loss) income from discontinued operations per common share - basic and diluted	(0.01)	0.01	(0.01)	0.01
Net (loss) income per common share - basic	(0.01)	0.01	0.02	0.06
Net (loss) income per common share - diluted	$ (0.01)	$ 0.01	$ 0.02	$ 0.05