Accessing Files Programmer's Guide (32650-90885)

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11 Accessing a File Using Mapped Access
A major enhancement to the MPE/iX file system is mapped file access, a method that
allows you to access a file directly through memory load and store instructions. Mapped
file access is available through three HPFOPEN intrinsic optional parameters:
• Item #18
short-mapped option returns a 32-bit value of type address.
• Item #21
long-mapped option returns a 64-bit value of type address.
• Item #87 large-mapped option returns a 64-bit value of type address. Long-mapped and
large-mapped options are identical with the exception that attempts to open a file
larger than 4GB - 64KB with the long-mapped option will result in a failure. The
large-mapped option may be used to open any file and is therefore considered more
reliable.