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Compare <a href="index.html#source file"><dfn>source file</dfn></a>.
See question <a href="../cpp/hfiles.html">10.6</a>.
</DD><DT><a name="H&amp;S">H&amp;S</a></DT>
<DD>The book
<I>C: A Reference Manual</I>,
by Samuel P. Harbison and
Guy L. Steele, Jr.
(see the Bibliography for a complete citation).
</DD><DT><a name="hosted environment">hosted environment</a></DT>
<DD>A C environment which also supports the C libraries.
Compare <a href="index.html#freestanding environment"><dfn>freestanding environment</dfn></a>.
(See ANSI Sec. 1.7 or ISO Sec. 4.)
</DD><DT><a name="idempotent">idempotent</a></DT>
<DD>adj.
Acting exactly once;
innocuous if re-applied.
In C,
usually refers to header files;
see questions <a href="../cpp/nestincl.html">10.7</a> and <a href="../ansi/pragmaonce.html">11.21</a>.
</DD><DT><a name="identifier">identifier</a></DT>
<DD>n.
A name,
usually having meaning
in a particular <a href="index.html#namespace"><dfn>namespace</dfn></a> and <a href="index.html#scope"><dfn>scope</dfn></a>.
See question <a href="../decl/namespace.html">1.29</a>.
</DD><DT><a name="implementation">implementation</a></DT>
<DD>n.
A compiler or other language translator,



together with its run-time libraries.
Used in constructions such as
``Whether plain <TT>char</TT> is signed or unsigned
is implementation-defined''
and
``These identifiers are reserved to the implementation.''
</DD><DT><a name="implementation-defined">implementation-defined</a></DT>
<DD>adj.
Refers to behavior which is not fully specified by the Standard
but which is required to be defined,
and documented,
by any particular implementation.

Example: whether plain <TT>char</TT> is signed or unsigned.
See question <a href="../ansi/undef.html">11.33</a>.
</DD><DT><a name="#include</> file"><TT>#include</TT> file</a></DT>
<DD>n.
A <a href="index.html#header file"><dfn>header file</dfn></a>.
</DD><DT><a name="incomplete type">incomplete type</a></DT>
<DD>n.
A type which is not completely specified,
but which may nevertheless be used in some contexts.
Examples:
dimensionless arrays;
structure or union types with tags but without member information.
(See ANSI Sec. 3.1.2.5 or ISO Sec. 6.1.2.5.)
</DD><DT><a name="in-band">in-band</a></DT>
<DD>adj.
Refers to a sentinel value
which is not always
unique within the set of values where it appears.
Compare <a href="index.html#out-of-band"><dfn>out-of-band</dfn></a>.
Example: CP/M or MS-DOS control-Z end-of-file markers.
See question <a href="../stdio/textvsbinary.html">12.40</a>.
</DD><DT><a name="indirect">indirect</a></DT>
<DD>vi.
To apply a level of indirection.
For example, to ``indirect on a pointer''
means
to chase
where the pointer points to
(as opposed to merely discovering the pointer's value).


See also <a href="index.html#dereference"><dfn>dereference</dfn></a>.
</DD><DT><a name="int"><TT>int</TT></a></DT>
<DD>n.
The integral type,
usually matching a machine's natural word size,
which is most often used
(and in some cases is used by default)
to represent integers in C.
</DD><DT><a name="integer">integer</a></DT>
<DD>n.
An integer of some size
(perhaps <TT>short</TT> or <TT>long</TT>),
not necessarily plain <TT>int</TT>.
</DD><DT><a name="integral">integral</a></DT>
<DD>adj.
Refers to a type which can represent integers.
The integral types in C are:
<TT>char</TT>,
three sizes of <TT>int</TT>
(<TT>short</TT>, plain, and <TT>long</TT>),
<TT>signed</TT> and <TT>unsigned</TT> variants of all of these,
and enumerations.
</DD><DT><a name="ISO">ISO</a></DT>
<DD>The International Organization for Standardization
or
Organisation Internationale de Normalisation.

</DD><DT><a name="K&amp;R">K&amp;R</a></DT>
<DD>n.
1.
The book
<I>The C Programming Language</I>
(see the Bibliography for a complete citation).
2.
That book's
authors,
Brian Kernighan and Dennis Ritchie.



adj.
Refers to the early version of C described in the first edition
(``K&amp;R1'') of the book.
</DD><DT><a name="lhs">lhs</a></DT>
<DD>n.
The left-hand side,
usually of an assignment,
or more generally,
of any binary operator.
</DD><DT><a name="lint"><TT>lint</TT></a></DT>
<DD>n.
A program written by Steve Johnson
as
companion to his <TT>pcc</TT>,
for performing cross-file and other error checking not normally
performed by C compilers.
The name supposedly derives from
the bits of fluff it picks from programs.
vt.
To check a program with <TT>lint</TT>.
</DD><DT><a name="little-endian">little-endian</a></DT>
<DD>adj.
Refers to storage of a multi-byte quantity
with the least-significant byte
at the lowest
address.
See also <a href="index.html#byte order"><dfn>byte order</dfn></a>.
</DD><DT><a name="lvalue">lvalue</a></DT>
<DD>n.
Originally,
an expression
which could appear
on the left-hand sign of an assignment operator,
hence,
something that can perhaps be assigned to.
More precisely,
something that has a location,
as opposed to a transient value.

In the assignment
<pre>
	a = b;
</pre>
<TT>a</TT> is an lvalue, and is not fetched, but is written to.
Compare <a href="index.html#rvalue"><dfn>rvalue</dfn></a>.
See also question <a href="../aryptr/arraylval.html">6.7</a>.
See ANSI Sec. 3.2.2.1 (especially footnote 31)
or ISO Sec. 6.2.2.1.
</DD><DT><a name="mask">mask</a></DT>
<DD>1.
n.
An integer value
which is intended specifically as a pattern of 1's and 0's
with which to perform bitwise operations
(<TT>&amp;</TT>, <TT>|</TT>, etc.).
2.
vt.
To select certain bits using a mask (sense 1) and a bitwise operator.
See question <a href="../misc/bitmanip.html">20.7</a>.
</DD><DT><a name="member">member</a></DT>
<DD>n.
One of the typed components
of a structure or union.
</DD><DT><a name="namespace">namespace</a></DT>
<DD>n.
A context within which names
(identifiers)
may be defined.
There are several namespaces in C;
for example,
an ordinary identifier can have the same name as a structure tag,
without ambiguity.
See question <a href="../decl/namespace.html">1.29</a>.
</DD><DT><a name="narrow">narrow</a></DT>
<DD>adj.
Refers to a type which is widened under the default argument promotions:
<TT>char</TT>, <TT>short</TT>, or <TT>float</TT>.
See questions <a href="../ansi/argpromos.html">11.3</a>
and <a href="../varargs/promos.html">15.2</a>.
</DD><DT><a name="nonreentrant">nonreentrant</a></DT>
<DD>adj.
Refers to
a piece of code which makes use of static memory,
or works with data structures which it temporarily leaves in an
inconsistent state,
such that it can not safely be called
while another instance of itself is already active.
(That is, it can not be called from an interrupt handler,
because it might have been the code interrupted.)

</DD><DT><a name="&ldquo;notreached&rdquo;">``notreached''</a></DT>
<DD>interj.
A directive
indicating to <TT>lint</TT>
or some other program checker
that control flow cannot reach a particular point,
and that certain warnings
(e.g. ``control falls off end of function without <TT>return</TT>'')
should therefore be suppressed.
See question <a href="../ansi/voidmain.html">11.12b</a>.
</DD><DT><a name="null pointer">null pointer</a></DT>
<DD>n.
A distinguished pointer value
which is not the address of any object or function.
See question <a href="../null/null1.html">5.1</a>.
</DD><DT><a name="null pointer constant">null pointer constant</a></DT>
<DD>n.
An integral constant expression with value 0
(or such an expression cast to <TT>void&nbsp;*</TT>),
used to request a <a href="index.html#null pointer"><dfn>null pointer</dfn></a>.
See question <a href="../null/null2.html">5.2</a>.
</DD><DT><a name="O(n)">O(n)</a></DT>
<DD>adj.
A notation referring to the ``order''
or computational complexity of an algorithm.
O(n) algorithms take time
roughly
proportional to the number of items operated upon.
O(n**2)
algorithms take time proportional to the square of the number of items, etc.
</DD><DT><a name="object">object</a></DT>
<DD>n.
Any piece of data that can be manipulated by a C program:
a simple variable, an array, a structure, a piece of <TT>malloc</TT>'ed memory,
etc.
See also <a href="index.html#object pointer"><dfn>object pointer</dfn></a>.
</DD><DT><a name="object pointer">object pointer</a></DT>
<DD>n.
A pointer
to any object or incomplete type.
Compare <a href="index.html#function pointer"><dfn>function pointer</dfn></a>.
</DD><DT><a name="octet">octet</a></DT>
<DD>n.
An 8-bit quantity.

Compare <a href="index.html#byte"><dfn>byte</dfn></a>.
</DD><DT><a name="opaque">opaque</a></DT>
<DD>adj.
Refers to a data type which is intended to be abstract:
code using the type is not supposed to know how
the type
is
implemented
(whether it is a simple type or a structure,
and if
a structure,
what fields it contains).
See question <a href="../struct/opaquetypes.html">2.4</a>.
</DD><DT><a name="order of evaluation">order of evaluation</a></DT>
<DD>n.
The order in which the operations implied by an expression

are actually carried out by the processor.
Compare <a href="index.html#precedence"><dfn>precedence</dfn></a>.
See question <a href="../expr/precvsooe.html">3.4</a>.
</DD><DT><a name="out-of-band">out-of-band</a></DT>
<DD>adj.
Refers to a sentinel
or otherwise exceptional
value which is distinct from all normal values
which can appear in some context
(e.g. in a set of
function return values, etc.).

Compare <a href="index.html#in-band"><dfn>in-band</dfn></a>.
Example: <TT>EOF</TT> (see question <a href="../stdio/getcharc.html">12.1</a>).
</DD><DT><a name="parameter">parameter</a></DT>
<DD>n.
The identifier in a function definition,
function-like macro definition,
or function prototype declaration
which stands for the actual argument which will be passed.
Often emphasized ``formal parameter.''
Compare <a href="index.html#argument"><dfn>argument</dfn></a>.
<br>
<br>
In the code
<pre>
	main()
	{
		f(5);
		return 0;
	}

	f(int i)
	{
	}
</pre>
the formal parameter of <TT>f</TT> is <TT>i</TT>
and the actual argument is <TT>5</TT>.
<br>In the fragment
<pre>
	extern int g(int apple);
	int orange = 5;
	g(orange);
</pre>
the formal parameter of <TT>g</TT> is <TT>apple</TT>
and the actual argument is <TT>orange</TT>.
</DD><DT><a name="pass by reference">pass by reference</a></DT>
<DD>n.
An argument passing mechanism in which a function receives
a reference to the actual argument,
such that if it modifies it,
it modifies the value in the caller.



Not available in C
(see question <a href="../ptrs/passbyref.html">4.11</a>).
</DD><DT><a name="pass by value">pass by value</a></DT>
<DD>n.
An argument passing mechanism in which a function receives
a copy of the actual argument,
such that if it modifies it,
it modifies only its own copy
(and does not affect the value in the caller).



Always used in C.
See questions
<a href="../ptrs/passptrinit.html">4.8</a>,
<a href="../malloc/ptrafterfree.html">7.21</a>,
and
<a href="../ptrs/passbyref.html">4.11</a>.
</DD><DT><a name="pcc"><TT>pcc</TT></a></DT>
<DD>n.
Steve Johnson's Portable C Compiler,
first written for the PDP-11
(as an alternative to Dennis Ritchie's <TT>cc</TT>)
circa
1978.


<TT>pcc</TT> was retargeted to the VAX during the Unix 32V and BSD
projects
and saw <em>very</em> wide distribution,
and served as the base for a large number of C compilers.
As much as K&amp;R1, it served as the <I>de facto</I> definition
of C for many years,
until X3J11 began its work.
(Note that the PCC mentioned in question <a href="../resources/compilers.html">18.3</a>
is probably no relation.)
</DD><DT><a name="precedence">precedence</a></DT>
<DD>n.
The ``strength'' of an operator,
indicating how tightly it binds to its operands during parsing,
especially as compared to other nearby operators.
Along with associativity and explicit parentheses,
precedence determines how an expression is parsed:
which operators are applied to which operands and
which subexpressions are the operands of which operators.
Precedence does not necessarily say anything about
<a href="index.html#order of evaluation"><dfn>order of evaluation</dfn></a> (q.v.);
see question <a href="../expr/precvsooe.html">3.4</a>.
</DD><DT><a name="preprocessor">preprocessor</a></DT>
<DD>n.
The part of a compiler
(traditionally, a separate program; hence the name)
which handles the <TT>#include</TT>, <TT>#define</TT>, <TT>#ifdef</TT>,
and related directives,
and performs substitution of <TT>#define</TT>d macros
in the rest of the
program source.
</DD><DT><a name="pointer context">pointer context</a></DT>
<DD>n.
An expression
context

in which it
can be recognized
that a pointer value is required.
The pointer contexts in C are:

<br>
<br>