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Appendix A: Making System Calls

The GNO Kernel is accessed through system calls. The actual procedure is very simple from C: simply #include the appropriate header file as noted in the synopsis of the call's manual page, and call it as you would any other C function. From assembly language the procedure is no more difficult, using the advanced macros provided for the APW and ORCA assemblers. Make sure, however, that you have defined a word variable errno. Lowercase is important, use the 'case on' and 'case off' directives to ensure that the definition of errno is case-sensitive. The system call interface libraries store any error codes returned by the kernel in this variable.

If you are going to be accessing the kernel from a language other than those for which interfaces are provided, then the following information is for you.