In Sybase ASE the database is hosted on devices which in turn are mapped to physical datafiles. So to create a database we should have devices already created, if not we can create new devices as:-

disk init name='<Device Name>', physname='<PATH where the datafile would be created>', size='<Size in MB>M', directio=true 
go

From the above command we can create devices for the database, ideally there should be separate devices for hosting data & log. Once we have the device created, database can be created using following commands.

create database <DB Name>
on <Device name for hosting data> = '<Size in MB>M' 
log on <Device name for hosting log> = '<Size in MB>M'
go