Code 128 supports all ASCII 128 characters.
Subset A supports numbers, upper-case letters, and control characters, such as tab and new-line.
Subset B supports numbers, upper- and lower-case letters
Subset C supports numbers only
BarCode Code 128 Auto
Advantage
•Check characters are computed automatically. You do not need to enter nor compute them.
•Use Code 128 Auto whenever possible. This setting will encode your data with the shortest possible number of bars.
•Control characters, such as TAB or NEW LINE, may be encoded by entering their three digit ASCII code prefixed by a caret (^).
For instance, "1234^009" will encode "1234" followed by a tab character (ASCII 009).
Professional apply
If you know your software requirement, it will be better for you to specify which subset to use. accidentally include in control character may cause the software appear abnormal. it also can control the unwanted character to be encoded into numeric only field.
Create your code 128 for free via below website:
http://www.alcaidc.com/Public/Solution/barcodegenerator/barcodeCode128.aspx