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<H1>Section 10: Program Structure and Compilation Issues</H1>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal"> [The overall structure of programs and the facilities
for separate compilation are described in this section. A <I>program</I>
is a set of <I>partitions</I>, each of which may execute in a separate
address space, possibly on a separate computer. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>1.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Glossary entry: </B>A <I>program</I>
is a set of <I>partitions</I>, each of which may execute in a separate
address space, possibly on a separate computer. A partition consists
of a set of library units.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>1.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Glossary entry: </B>A <I>partition</I>
is a part of a program. Each partition consists of a set of library units.
Each partition may run in a separate address space, possibly on a separate
computer. A program may contain just one partition. A distributed program
typically contains multiple partitions, which can execute concurrently.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>2</FONT></DIV>
<DIV Class="Normal"> <A NAME="I3836"></A><A NAME="I3837"></A><A NAME="I3838"></A>As
explained below, a partition is constructed from <I>library units</I>.
Syntactically, the declaration of a library unit is a <FONT FACE="Arial, Helvetica">library_item</FONT>,
as is the body of a library unit. An implementation may support a concept
of a <I>program library</I> (or simply, a ``library''), which contains
<FONT FACE="Arial, Helvetica">library_item</FONT>s and their subunits.
<A NAME="I3839"></A>Library units may be organized into a hierarchy of
children, grandchildren, and so on.]</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3</FONT></DIV>
<DIV Class="Normal"> This section has two clauses: <A HREF="AA-10-1.html">10.1</A>,
``<A HREF="AA-10-1.html">Separate Compilation</A>'' discusses compile-time
issues related to separate compilation. <A HREF="AA-10-2.html">10.2</A>,
``<A HREF="AA-10-2.html">Program Execution</A>'' discusses issues related
to what is traditionally known as ``link time'' and ``run time'' -- building
and executing partitions.</DIV>
<H4 ALIGN=CENTER>Language Design Principles</H4>
<DIV Class="Paranum"><FONT SIZE=-2>3.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><A NAME="I3840"></A>We should
avoid specifying details that are outside the domain of the language
itself. The standard is intended (at least in part) to promote portability
of Ada programs at the source level. It is not intended to standardize
extra-language issues such as how one invokes the compiler (or other
tools), how one's source is represented and organized, version management,
the format of error messages, etc.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><A NAME="I3841"></A><A NAME="I3842"></A>The
rules of the language should be enforced even in the presence of separate
compilation. Using separate compilation should not make a program less
safe.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3.c</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><A NAME="I3843"></A>It should
be possible to determine the legality of a compilation unit by looking
only at the compilation unit itself and the compilation units upon which
it depends semantically. As an example, it should be possible to analyze
the legality of two compilation units in parallel if they do not depend
semantically upon each other.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3.d</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>On the other hand, it may be necessary
to look outside that set in order to generate code -- this is generally
true for generic instantiation and inlining, for example. Also on the
other hand, it is generally necessary to look outside that set in order
to check Post-Compilation Rules.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3.e</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>See also the ``generic contract
model'' Language Design Principle of <A HREF="AA-12-3.html">12.3</A>,
``<A HREF="AA-12-3.html">Generic Instantiation</A>''. </FONT></DIV>
<H4 ALIGN=CENTER>Wording Changes from Ada 83</H4>
<DIV Class="Paranum"><FONT SIZE=-2>3.f</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>The section organization mentioned
above is different from that of RM83. </FONT></DIV>
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