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| author | Tobias Klauser <tklauser@distanz.ch> | 2008-01-27 11:37:44 +0100 |
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| committer | Tobias Klauser <tklauser@xenon.tklauser.home> | 2008-01-27 11:37:44 +0100 |
| commit | 7e0f021a9aec35fd8e6725e87e3313b101d26f5e (patch) | |
| tree | b1cacc4b24393f517aeb4610e9e1021f954307a8 /reference/C/FUNCTIONS/malloc.html | |
Initial import (2.0.2-6)2.0.2-6
Diffstat (limited to 'reference/C/FUNCTIONS/malloc.html')
| -rw-r--r-- | reference/C/FUNCTIONS/malloc.html | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/reference/C/FUNCTIONS/malloc.html b/reference/C/FUNCTIONS/malloc.html new file mode 100644 index 0000000..d4f7e0f --- /dev/null +++ b/reference/C/FUNCTIONS/malloc.html @@ -0,0 +1,123 @@ +<title>malloc function</title> + +<head> +<script language="JavaScript"> +</script> +</head> + +<body bgcolor=#ffffcc> +<hr> +<center> +<h1>malloc function </h1> +</center> +<hr> +<b>malloc</b> (memory allocation) is used to dynamically allocate memory +at run time. Possible uses for this function are: + +<ul> +<li>Read records of an unknown length. +<li>Read an unknown number of database records. +<li><a href="../MISC/linklists.html">Link lists</a>. +</ul> + +The simplest way to reserve memory is to code something like: +<p> +<table border=2 width=100% bgcolor=ivory> +<tr> +<td> +<pre> + + main() + { + char string[1000]; + + <a href="strcpy.html">strcpy</a> (string, "Some text"); + } +</pre> +</tr> +</td> +</table> +<p> +The example above has two problems: +<ul> +<li>If the data is less than + +1000 bytes we are wasting memory. +<li>If the data is greater than 1000 bytes the program is going to crash. +<li>The 1000 bytes are reserved throught out the life of the program. +If this was a long running program that rarely used the memory, it would +again be wasteful. +</ul> +malloc allows us to allocate exactly the correct amount of memory and +with the use of <a href="free.html">free</a> only for the time it is required. +<p> +<hr> +<pre> + Library: stdlib.h + + Prototype: void *malloc(size_t size); + + Syntax: char * String; + + String = (char *) malloc(1000); +</pre> +<hr> +<p> +Looking at the example syntax above, 1000 bytes are reserved and the pointer +<b>String</b> points to the first byte. The 1000 bytes are NOT initialized +by malloc. If the memory is NOT available, a +<a href="../SYNTAX/null.html">NULL</a> pointer is returned. + +Please note, the cast <a href="../CONCEPT/cast.html">cast</a> is required to +return a pointer of the correct type. +<h2>Examples:</h2> + +<img src="../../GRAPHICS/computer.gif"><a href="../EXAMPLES/linklst1.c"> example</a> +program. + +<p> +<hr> +<h2>See Also:</h2> +<img src=../../GRAPHICS/whiteball.gif> +<a href="../CONCEPT/data_types.html#char">char</a> data type.<p> +<img src=../../GRAPHICS/whiteball.gif> +<a href="free.html">free</a> function.<p> + +<img src=../../GRAPHICS/whiteball.gif> +<a href="../SYNTAX/sizeof.html">sizeof</a> operator.<p> +<hr> +<font color=brown> +<h2>C++</h2> +<img src=../../GRAPHICS/whiteball.gif> +<a href="../../CPLUSPLUS/SYNTAX/new.html">new</a> is the C++ equivalent to malloc.<p> + +<img src=../../GRAPHICS/whiteball.gif> +<a href="../../CPLUSPLUS/SYNTAX/delete.html">delete</a> is the C++ equivalent to +<a href="free.html">free</a>.<p> +</font> + +<p> + +<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="funcref.htm"> Functions</a> +</td> +</tr> +</table> +</center> +<p> +<hr> +<address>Martin Leslie +</address><p> +</body> +</html> |