You can either connect your ABL session to a database with a client session startup parameter or programmatically, with the connect
statement.
Startup parameter
Using a startup parameter would look like:
<session command> [-db] <physical db name/path> [other parameters]
The <session command> could be a shell script, like pro/bpro/mpro/mbpro, or a client executable like _progres/prowin/prowin32.
If you are connecting self-service, then the <name/path> is an absolute or relative path, ending with the database name. If you are connecting remotely (i.e. specifying -S <port number or service name>) then <name/path> is the logical name of the database.
Programmatically
Connecting to a database at run time involves the connect
statement. It is documented in the ABL Reference manual. Reading that is left as an exercise for the reader.