The compiler uses Linker global symbols to resolve external references. Because the Linker does not permit the percent sign (%) in a symbol name, GT.M converts any legal occurrences of the percent sign to an underscore (_).

The Linker does not permit lower case letters in global symbol names. The compiler converts routine names to upper case, and optionally maintains case sensitivity for labels. Note this requires attention in cases where you would otherwise distinguish routine names only by case.

The most common error for the Linker to detect is an undefined global symbol. Usually, the undefined global symbol results from mistyping a routine or label name, or leaving a module out of the Link parameter list. The Linker produces an image even when it encounters an undefined symbol. VMS can run an image with unresolved symbols as long as no instructions attempt to use the "missing" symbols.

For more information on Linker error messages refer to the VMS Linker Reference Manual.