HP-33s and HP-35s lack min and max functions. Yes, they could be easily programmed, but..

a) Label would be consumed on HP-33S (not a problem for HP-35S, thou)

b) You can't use conditionals in the Equation Writer

So, here is simple (but awkward) brute force implementation of MIN & MAX using Signum function, present on these calculators.

MIN(a,b)=((b-a)*SGN(a-b)+b+a)/2

MAX(a,b)=((a-b)*SGN(a-b)+b+a)/2

If used in program, they could be simplified by isolating (a-b).