This
topic describes
how to perform memory file and hiperspace I/O operations.
z/OS® XL C/C++ supports
files known as
memory files. Memory files
are temporary work files that are stored in main memory rather than
in external storage. There are two types of memory files:
- Regular memory files, which exist in your virtual storage
- Hiperspace™ memory files, which use special storage
areas called hiperspaces.
Memory files can be written to, read from, and repositioned within
like any other type of file. Memory files exist for the life of your
root program, unless you explicitly delete them by using the
remove() or
clrmemf() functions.
The root program is the first
main() to be invoked. Any
main() program
called by a
system() call is known as a
child program.
When the root program terminates,
z/OS XL C/C++ removes memory files automatically.
Memory files may give you better performance than other types of files.
Note: There
may not be a one-to-one correspondence between the bytes in a memory
file and the bytes in some other external representation of the file,
such as a disk file. Applications that mix open modes on a file (for
example, writing a file as text file and reading it back as binary)
may not port readily from external I/O to memory file I/O.
This topic describes
C I/O streams as they can be used within C++ programs. If you want
to use the C++ I/O stream classes instead, see Using the Standard C++ Library I/O Stream Classes for
general information. For more detailed information, see Standard C++ Library Reference,
which discusses the Standard C++ I/O stream classes.