The shared and side-by-side versions of the LabWindows/CVI Run-Time Engine (RTE) differ in the following ways when you install a new version of the RTE.

• Shared RTE—Installing a new version of the default shared RTE upgrades the previous version of the RTE. The default RTE is backward compatible and can execute LabWindows/CVI executables or DLLs built with previous versions of LabWindows/CVI. However, the executables or DLLs might not behave exactly the same way as a result of changes in the RTE code. For example, optimizations in the RTE might result in functions executing faster than in previous versions of the RTE.
• Side-by-Side RTE—Because the side-by-side version of the RTE is version-specific, installing a new version of the side-by-side RTE prevents any behavior changes to applications built with older versions of LabWindows/CVI. Previously built LabWindows/CVI applications behave identically because they continue to call the same version of the side-by-side RTE they originally called.

For most applications, NI recommends that you use the default shared RTE. However, if the test system requires validation, use the side-by-side version of the RTE to minimize the amount of validation required. For example, if you start using a new LabWindows/CVI feature in a code module, you must install a new version of the LabWindows/CVI RTE on test stations that use the test system. If you use the shared RTE, you would validate the entire test system after you installed a new LabWindows/CVI RTE because the behavior of DLLs could change using the new version of the RTE. If you use the side-by-side RTE, you would validate only the new code because the old code continues to call the same RTE version it did before.