can check a car battery using digital multimeter exactly ?

Yes, you can check use a multi meter. The readings you are getting are good for the battery. With the engine running, it should increase. As far as the no start, is the starter engaging?

Dear Sirs, My morris minor 1000 car can not start Pleas tel me what happened ?
hints
Difficult to start ,Start mortar is slip
start and stop the engine
when start ,the engine is tuning weakly
Petrol pump weak supply
ignition warming light is not off
I check my car battery using digital multimeter it Read 12.48v (in 20v position of multimeter) and it read 12.2 (in 200v position of multimeter)
My car is not start now - what is the problem ? Car is had not been run 1 month ,but I start the car and off everyday (befor 2 days I started the car )- Battery Ampere is low ?

have the battery load tested, 12V surface charge is no indication as to battery condition, if fuel pressure is poor, repair fuel pump, is it a mechanical or an older SU electric pump? are the compressions ok?