This is a fully-automatic calculator. The features include tabulator buttons for predetermining the number of decimal places in division, as well as fixed decimal point alignment in multiplication. Once decimal points are set, they remain correct throughout all calculations. As for all automatic machines, there is an additional Register, the “Control Register”, also named “Register V”. This is necessary because, in automatic multiplication, the first factor in a product has to be stored while the second is set up.

It must be pointed out that the 20BS, as the 20BZS, has no “Carriage Return Lever”. On all other automatic models, this lever is situated on “Register V”, at left. See the difference, for example, with model 20BTG or 20BTZG. This control permits to disengage the mechanism whereby, after multiplication, the carriage is returned automatically to its normal extreme left position.
The main external difference with the model 20AS is the red key at the left of the “multiplication bar”, which replaces the lever “+/-” for negative multiplication.
Model 20BS (or 20AS), like the 20A and 20AV, is very special among calculators in that it is possible, by engaging a special lever situated under dials 20 and 19 of “Register I”, to form the quotient when dividing not only in “Register II” but, simultaneously, in the left of “Register I”, as the remainder diminishes. By means of this facility, a quotient may be transferred directly into the Register V for use in subsequent multiplication.
We can see this feature on the picture below: