Concept:
Each letter is represented by its alphabetical position, and the code is the sum of these positions.
Step 1: Verify with COVER.
\[
C(3) + O(15) + V(22) + E(5) + R(18)
= 3 + 15 + 22 + 5 + 18 = 63
\]
Step 2: Apply to BASIS.
\[
B(2) + A(1) + S(19) + I(9) + S(19)
= 2 + 1 + 19 + 9 + 19 = 50
\]
Hence, the code for BASIS is 50.