CALL_EXTERNAL can call external functions contained in shareable object libraries. On Windows platforms this means Windows compatible DLLs. CALL_EXTERNAL does not check the number of or type of parameters, which must therefore be checked carefully by the programmer to avoid corrupted data or crashes.
LINKIMAGE merges routines written in other languages with IDL at run-time. Due to time constraints, this procedure was not reviewed, but according to the manual:
Using LINKIMAGE requires intimate knowledge of the internals of IDL… It should only be used if there is absolutely no alternative.
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