Designing a circuits in mind.

I am visioning an Engineer who don't see the truth table of logic gates and many other devices like BJT,FET etc and test the circuit outputs directly in mind .

And Gate- Non expert person Knows that if any i/p 0 then o/p 0 but side by side to become expert you should also know if both i/p 1 o/p 1

i.e say if any        i/p 0 then o/p 0
            if both/all i/p 1 then o/p 1


For Nand Gate

you know it is an invert of above gate but you might don't grab below thing

i.e say if any        i/p 0 then o/p 1
            if both/all i/p 0 then o/p 0

Or Gate
Non expert person Knows that if any i/p 1 then o/p 1 but side by side to become expert you should also know if both i/p 0 o/p 0

i.e say if any        i/p 1 then o/p 1
            if both/all i/p 0 then o/p 0



similarly remember for other gates also

What More you should Know
BJT peactical working
FET practical working
Monostable
Bistable