Hi Senthiljith,
In the earlier days of computers (meaning mainframes), data files resided on devices that had to be constantly removed and installed. These devices included disks, tapes, 'drums', cards, perforated cards, etc...
This created a few problems. The operating system executed different I/O routines depending on which device was being referenced. Also, the possibility existed that data files on different devices could share the same name. Therefore another level of data file identification was needed: LABEL each device.
This technique of LABELing device still exists to this day. For example, insert a blank compact disc in your CD drive. Expand 'My Computer'. Your CD drive should simply say "CD Drive". Now insert, say, your COBOL installation disk in the CD drive. That drive should now display something other than just 'CD Drive'. That is your LABEL.
If this were an earlier computer, you wouldn't have the luxury of 'knowing' the drive letter (M
that holds the disc; but, using the LABEL would find it for you.
Today, COBOL considers 'LABEL RECORD...' obsolete: you are advised to not use it in new applications. Modern computer architectures no longer support LABELing, they use disc drive names; and, besides, the trend for operating systems is to treat all devices in a consistent manner: the same I/O statements should work transparently the same way on any file residing on any device.
Dimandja
