After the compiler produces object code, the object code must be combined with other object modules and mapped into memory. GT.M provides two ways to accomplish this: the GT.M command ZLINK and/or the VMS LINK utility. Most programmers in a development environment prefer to use ZLINK, as it provides them with the "touch and feel" of an interpreter for greater programming productivity. Depending on various factors, including the size of the application and the frequency of use of its component routines, using LINK to supplement production images may be advantageous.
The following table compares ZLINK and LINK.
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Comparison of ZLINK and LINK |
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ZLINK |
LINK |
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Works on a running image |
Produces a new image |
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Lasts until image terminates or another ZLINK of the same module |
Produces a reusable .EXE file |
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Adds object files individually |
Combines all required object files |
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Defers resolution of references until used |
Treats unresolved references as errors |
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May invoke the GT.M compiler |
Requires a properly prepared set of object modules |
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Incremental approach allows changes with minimum impact |
Changes require complete reconstruction and therefore longer turnaround times |
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Run-time cost is modest without compile, may be noticeable with compile |
No run-time cost |
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Each image must have its own copy of the machine code |
Resulting image may be shared for better performance |