There are several ways to backup a database, it depends if the server is running or not, if you want to backup just the transaction log or also the '.db'.
Keep in mind that backup itself is just a process of coping the files in a safe place to replace the originals if something goes wrong, that means that you can make a program to just copy the files somewhere for backup, but this methods needs the server to be offline. Another way is using sybase's utilitys, for example you can create a program that uses the dbbackup, dbshrink or dbtool, the syntax and help are in the help of sybase.
Try searching the sybase web site for backups methods and tips.
It also depends on the version of sybase.
Hope this helps,
David.