In Wasp Fontware, Code 128 automatically includes Code 128 A, B, C:

Wasp Fontware selects the specific subset based on the data that used to create the barcode.

Wasp Fontware can encode Code 128 codes that contain multiple subsets also. We do this by switching between all 3 character sets of Code 128: 

Code 128A: Includes upper case letters and control characters.
Code 128B: Includes upper and lower case letters.
Code 128C: Specially optimized for numbers.

Fontware v5