Ada 95 Quality and Style Guide | Chapter 7 |
The types of portability problems encountered with I/O tend to
be different for applications running with a host operating system
versus embedded targets where the Ada run-time is self-sufficient.
Interacting with a host operating system offers the added complexity
of coexisting with the host file system structures (e.g., hierarchical
directories), access methods (e.g., indexed sequential access
method [ISAM]), and naming conventions (e.g., logical names and
aliases based on the current directory). The section on Input/Output
in ARTEWG (1986) provides some examples of this kind of dependency.
Embedded applications have different dependencies that often tie
them to the low-level details of their hardware devices.
The major defense against these inherent implementation dependencies
in I/O is to try to isolate their functionality in any given application.
The majority of the following guidelines are focused in this direction.
7.7 INPUT/OUTPUT
I/O facilities in Ada are not a part of the syntactic definition
of the language. The constructs in the language have been used
to define a set of packages for this purpose. These packages are
not expected to meet all the I/O needs of all applications, in
particular, embedded systems. They serve as a core subset that
may be used on straightforward data and that can be used as examples
of building I/O facilities upon the low-level constructs provided
by the language. Providing an I/O definition that could meet the
requirements of all applications and integrate with the many existing
operating systems would result in unacceptable implementation
dependencies.
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