summaryrefslogtreecommitdiff
path: root/reference/C/CONCEPT/constants.html
diff options
context:
space:
mode:
authorTobias Klauser <tklauser@distanz.ch>2008-01-27 11:37:44 +0100
committerTobias Klauser <tklauser@xenon.tklauser.home>2008-01-27 11:37:44 +0100
commit7e0f021a9aec35fd8e6725e87e3313b101d26f5e (patch)
treeb1cacc4b24393f517aeb4610e9e1021f954307a8 /reference/C/CONCEPT/constants.html
Initial import (2.0.2-6)2.0.2-6
Diffstat (limited to 'reference/C/CONCEPT/constants.html')
-rw-r--r--reference/C/CONCEPT/constants.html143
1 files changed, 143 insertions, 0 deletions
diff --git a/reference/C/CONCEPT/constants.html b/reference/C/CONCEPT/constants.html
new file mode 100644
index 0000000..e2a7778
--- /dev/null
+++ b/reference/C/CONCEPT/constants.html
@@ -0,0 +1,143 @@
+<title>Constants</title>
+<body bgcolor="#ffffcc">
+<hr>
+<center><h1>Constants</h1></center>
+<hr>
+Be sure you understand the difference between a 'constant' and a
+<a href=../glossary.html#declaration>declaration</a>.
+A constant has a value that cannot be changed. For example:
+<pre>
+
+ 1234
+ 'x'
+ 9.89
+ "String"
+
+</pre>
+Constants are used to assign a value to a variable. E.G
+<pre>
+ int i; /* declare a variable called 'i' */
+ i=1234; /* assign the constant value 1234 to
+ * the variable 'i' */
+ i++; /* Change the value of the variable. */
+</pre>
+<ul>
+<li><a href="#int">Integer constants.</a>
+<li><a href="#float">Floating point constants.</a>
+<li><a href="#char">Character constants.</a>
+<li><a href="#str">String constants.</a>
+</ul>
+<hr>
+<h2><a name=int>Integer constants.</h2>
+Interger constants can be expressed in the following ways.
+<pre>
+ 1234 (decimal)
+ 0xff (Hexidecimal)
+ 0100 (Octal)
+ '\xf' (Hex character)
+</pre>
+Examples of their use are:
+<pre>
+ int i=255; /* i assigned the decimal value of 255 */
+
+ i-=0xff /* subtract 255 from i */
+
+ i+=010 /* Add Octal 10 (decimal 8) */
+
+ /* Print 15 - there are easier ways... */
+ printf ("%i \n", '\xf');
+
+</pre>
+Integer constants are assumed to have a datatype of
+<a href=data_types.html#int> int</a>, if it will not fit into an 'int'
+the compiler will assume the constant is a
+<a href=data_types.html#modifier>long</a>. You may also force the
+compiler to use 'long' by putting an 'L' on the end of the
+integer constant.
+<pre>
+ 1234L /* Long int constant (4 bytes) */
+</pre>
+The other modifier is 'U' for Unsigned.
+<pre>
+ 1234U /* Unsigned int */
+</pre>
+and to complete the picture you can specify 'UL'
+<pre>
+ 1234UL /* Unsigned long int */
+</pre>
+
+<hr>
+<h2><a name=float>Floating point constants.</h2>
+Floating point constants contain a decimal point or exponent. By default
+they are <a href=data_types.html#double>double</a>.
+<pre>
+ 123.4
+ 1e-2
+
+
+<hr>
+</pre>
+<h2><a name=char>Chararacter constants.</h2>
+Are actually integers.
+<pre>
+ 'x'
+ '\000'
+ '\xhh'
+
+ <a href=../FUNCTIONS/escape.html>escape sequences</a>
+
+</pre>
+
+<hr>
+</pre>
+<h2><a name=str>String constants.</h2>
+
+Strings do not have a <a href=data_types.html>datatype</a> of their own.
+They are actually a sequence of char items terminated with a
+<a href=../SYNTAX/null.html>\0</a>. A string can be accessed with a
+<b>char</b> pointer.
+<p>
+An example of a string would be:
+<pre>
+
+ char *Str = "String Constant";
+
+</pre>
+
+See the discussion on <a href=../CONCEPT/string.html>
+strings</a> for more information.
+<p>
+
+<hr>
+<h2>Also see:</h2>
+<ul>
+<li><a href=../SYNTAX/define_preprocessor.html>#define</a>
+<li><a href=../CONCEPT/string.html>Strings</a>
+</ul>
+<hr>
+<p>
+<center>
+<table border=2 width=80% bgcolor=ivory>
+<tr align=center>
+<td width=25%>
+<a href="../cref.html">Top</a>
+</td><td width=25%>
+<a href="../master_index.html">Master Index</a>
+</td><td width=25%>
+<a href="../SYNTAX/keywords.html">Keywords</a>
+</td><td width=25%>
+<a href="../FUNCTIONS/funcref.htm">Functions</a>
+</td>
+</tr>
+</table>
+</center>
+<p>
+
+<hr>
+<address>Martin Leslie
+<script language="JavaScript">
+<!-- //
+document.write(document.lastModified);
+// -->
+</script>
+</address>