Meaning of Alphabets in HP Product Version Names

[RebeccaS_1]

Does anyone know the meaning/ significance behind the alphabets in HP product version names?
Eg: Serviceguard A.11.19 ( Can be A or B)

[Dennis Handly]

Probably just sequential letters with major changes between them?

[melvyn burnard]

In some cases it can be an indicator of which OS version it runs on.
Vpars for example:
T1335ACE <- for 11iv1 (11.11)
T1335BCE <- for 11iv2 (11.23)
T1335CCE <- for 11iv3 (11.31)

[Dennis Handly]

My comment was for an initial letter.
Trailing letters are for different options as Melvyn mentioned.

[RebeccaS_1]

Thank you for your responses.

I was referring to the initial letter too.
However, i guess there is no explainable reason or specific significance behind them.