What Are Links?
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Linking is an optional feature that allows you to combine survey files that have duplicate station names. With linking, you tell the compiler which stations are to be used to connect two cave files together. Linking tells the compiler to remember only the linking stations and forget all other stations between files. This way, duplicate station names do not interfere with each other.
Linking is only required when you have duplicate station names. However, there are some other circumstances where linking can be useful. For one thing, linked files compile slightly faster because the compiler doesn't have to remember so many stations at one time. For another, the DOS version of COMPASS requires linking on large files because of the memory limitations of DOS. Windows does not have memory limitations, but if you plan to use your files with COMPASS for DOS, you may want to use links.
Links specify the station or stations in an old file that makes the connection to the new file. You can have up to 500 links between files. The value of linking is that after the compiler has been given all the linking stations, it can forget all other stations in the old file. This also frees up a large block of memory.
As an example, here are two very simple survey files, with the shots shown afterward:
COW.DAT - A1->A2 A2->A3 A3->A4
TREE.DAT - A3->B1 B1->B2 B2->B3
You will notice that the station A3 is first defined in COW.DAT. It appears again in TREE.DAT where it defines the connection between COW.DAT and TREE.DAT. That means that to process TREE.DAT, the only thing the program needs to know about is A3. It can forget about everything else in COW.DAT but A3. For this reason, we need tell the program that A3 is the connection. As a result, the linking information for the two files would be:
COW.DAT -- No Links
TREE.DAT -- A3
You will notice that the link A3 is specified for TREE.DAT, not COW.DAT. This is because the program does not need any links to process COW.DAT because it is the first file to be processed. Since the program only needs to know that A3 is the link when it begins processing TREE.DAT, you must put the linking station with TREE.DAT.