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Allegro Manual: Using Allegro
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<h1><a name="Using Allegro">Using Allegro</a></h1>

<ul>
<li><a href="#AL_ID">AL_ID</a> &mdash; Converts four 8 bit values to a packed 32 bit integer ID.
<li><a href="#ALLEGRO_DATE">ALLEGRO_DATE</a> &mdash; Defined to a number with the release date of Allegro.
<li><a href="#ALLEGRO_DATE_STR">ALLEGRO_DATE_STR</a> &mdash; Defined to a string with the year Allegro was released.
<li><a href="#allegro_error">allegro_error</a> &mdash; Stores the last Allegro error message.
<li><a href="#allegro_exit">allegro_exit</a> &mdash; Closes down the Allegro system.
<li><a href="#allegro_id">allegro_id</a> &mdash; String containing date and version number of Allegro.
<li><a href="#allegro_init">allegro_init</a> &mdash; Macro to initialise the Allegro library.
<li><a href="#allegro_message">allegro_message</a> &mdash; Used mainly to show error messages to users.
<li><a href="#ALLEGRO_SUB_VERSION">ALLEGRO_SUB_VERSION</a> &mdash; Defined to the middle version of Allegro.
<li><a href="#ALLEGRO_VERSION">ALLEGRO_VERSION</a> &mdash; Defined to the major version of Allegro.
<li><a href="#ALLEGRO_VERSION_STR">ALLEGRO_VERSION_STR</a> &mdash; Defined to a string with the full Allegro version number.
<li><a href="#ALLEGRO_WIP_VERSION">ALLEGRO_WIP_VERSION</a> &mdash; Defined to the minor version of Allegro.
<li><a href="#check_cpu">check_cpu</a> &mdash; Detects the CPU type.
<li><a href="#cpu_capabilities">cpu_capabilities</a> &mdash; Contains the capability flags of the CPU.
<li><a href="#cpu_family">cpu_family</a> &mdash; Contains the CPU type.
<li><a href="#cpu_model">cpu_model</a> &mdash; Contains the Intel CPU submodel.
<li><a href="#cpu_vendor">cpu_vendor</a> &mdash; Contains the CPU vendor name.
<li><a href="#desktop_color_depth">desktop_color_depth</a> &mdash; Finds out the desktop color depth.
<li><a href="#END_OF_MAIN">END_OF_MAIN</a> &mdash; Macro to put after your main() function.
<li><a href="#get_desktop_resolution">get_desktop_resolution</a> &mdash; Finds out the desktop resolution.
<li><a href="#install_allegro">install_allegro</a> &mdash; Initialise the Allegro library.
<li><a href="#MAKE_VERSION">MAKE_VERSION</a> &mdash; Create a 32 bit integer from the Allegro version
<li><a href="#os_multitasking">os_multitasking</a> &mdash; Indicates if the OS is multitasking.
<li><a href="#os_revision">os_revision</a> &mdash; Version of the OS currently running.
<li><a href="#os_type">os_type</a> &mdash; Stores the detected type of the OS.
<li><a href="#os_version">os_version</a> &mdash; Version of the OS currently running.
<li><a href="#set_close_button_callback">set_close_button_callback</a> &mdash; Handles the user clicking on the close button of the window.
<li><a href="#set_window_title">set_window_title</a> &mdash; Sets the window title of the Allegro program.
</ul>

<p>
See <a href="readme.html">readme.txt</a> for a general introduction, copyright details, and 
information about how to install Allegro and link your program with it.

<p><br>
<div class="al-api"><b>int <a name="install_allegro">install_allegro</a>(int system_id, int *errno_ptr, int (*atexit_ptr)());</b></div><br>
   Initialises the Allegro library. You must call either this or 
   allegro_init() before doing anything other than using the Unicode 
   routines. If you want to use a text mode other than UTF-8, you can set
   it with set_uformat() before you call this. The other functions that can
   be called before this one will be marked explicitly in the documentation,
   like set_config_file().

<p>
   The available system ID codes will vary from one platform to another, but
   you will almost always want to pass SYSTEM_AUTODETECT. Alternatively,
   SYSTEM_NONE installs a stripped down version of Allegro that won't even
   try to touch your hardware or do anything platform specific: this can be
   useful for situations where you only want to manipulate memory bitmaps,
   such as the text mode datafile tools or the Windows GDI interfacing
   functions.

<p>
   The <tt>`errno_ptr'</tt> and <tt>`atexit_ptr'</tt> parameters should point to the errno
   variable and atexit function from your libc: these are required because
   when Allegro is linked as a DLL, it doesn't have direct access to your
   local libc data. <tt>`atexit_ptr'</tt> may be NULL, in which case it is your
   responsibility to call allegro_exit() manually. Example:
<blockquote class="code"><pre>
      <a href="#install_allegro" class="autotype" title="Initialise the Allegro library.">install_allegro</a>(SYSTEM_AUTODETECT, &amp;errno, atexit);</pre></blockquote>
<p><b>Return value:</b>
   This function returns zero on success and non-zero on failure (e.g. no
   system driver could be used). Note: in previous versions of Allegro this
   function would abort on error.


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#allegro_init" title="Macro to initialise the Allegro library.">allegro_init</a>,
<a class="xref" href="#allegro_exit" title="Closes down the Allegro system.">allegro_exit</a>,
<a class="xref" href="alleg002.html#set_uformat" title="Set the global current text encoding format.">set_uformat</a>,
<a class="xref" href="alleg003.html#set_config_file" title="Sets the configuration file.">set_config_file</a>.</blockquote>
<div class="al-api"><b>int <a name="allegro_init">allegro_init</a>();</b></div><br>
   Macro which initialises the Allegro library. This is the same thing as
   calling install_allegro(SYSTEM_AUTODETECT, &amp;errno, atexit).


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#install_allegro" title="Initialise the Allegro library.">install_allegro</a>,
<a class="xref" href="#allegro_exit" title="Closes down the Allegro system.">allegro_exit</a>.</blockquote>

<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg045.html#Available Allegro examples" title="">Available Allegro examples</a>.</blockquote>
<div class="al-api"><b>void <a name="allegro_exit">allegro_exit</a>();</b></div><br>
   Closes down the Allegro system. This includes returning the system to
   text mode and removing whatever mouse, keyboard, and timer routines have
   been installed. You don't normally need to bother making an explicit call
   to this function, because allegro_init() installs it as an atexit()
   routine so it will be called automatically when your program exits.

<p>
   Note that after you call this function, other functions like
   destroy_bitmap() will most likely crash. This is a problem for C++ global
   destructors, which usually get called after atexit(), so don't put Allegro
   calls in them. You can write the destructor code in another method which
   you can manually call before your program exits, avoiding this problem.


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#install_allegro" title="Initialise the Allegro library.">install_allegro</a>,
<a class="xref" href="#allegro_init" title="Macro to initialise the Allegro library.">allegro_init</a>,
<a class="xref" href="alleg009.html#destroy_bitmap" title="Destroys any type of created bitmap.">destroy_bitmap</a>.</blockquote>

<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg045.html#ex3d" title="3d 'bouncy cubes' demo.">ex3d</a>,
<a class="eref" href="alleg045.html#exscn3d" title="Using the 3d scene functions.">exscn3d</a>,
<a class="eref" href="alleg045.html#exswitch" title="Controlling the console switch mode for background running.">exswitch</a>,
<a class="eref" href="alleg045.html#exxfade" title="Truecolor image loading and fades.">exxfade</a>,
<a class="eref" href="alleg045.html#exzbuf" title="Z-buffered polygons demo.">exzbuf</a>.</blockquote>
<div class="al-api"><b>Macro <a name="END_OF_MAIN">END_OF_MAIN</a>()</b></div><br>
   In order to maintain cross-platform compatibility, you have to put this
   macro at the very end of your main function. This macro uses some <tt>`magic'</tt>
   to mangle your main procedure on platforms that need it like Windows,
   some flavours of UNIX or MacOS X. On the other platforms this macro 
   compiles to nothing, so you don't have to #ifdef around it. Example:
<blockquote class="code"><pre>
      int main(void)
      {
         <a href="#allegro_init" class="autotype" title="Macro to initialise the Allegro library.">allegro_init</a>();
         /* more stuff goes here */
         ...
         return 0;
      }
      <a href="#END_OF_MAIN" class="autotype" title="Macro to put after your main() function.">END_OF_MAIN</a>()</pre></blockquote>


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="alleg037.html#Windows specifics" title="">Windows specifics</a>,
<a class="xref" href="alleg038.html#Unix specifics" title="">Unix specifics</a>,
<a class="xref" href="alleg041.html#MacOS X specifics" title="">MacOS X specifics</a>,
<a class="xref" href="alleg042.html#Differences between platforms" title="">Differences between platforms</a>.</blockquote>

<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg045.html#Available Allegro examples" title="">Available Allegro examples</a>.</blockquote>
<div class="al-api"><b>extern char <a name="allegro_id">allegro_id</a>[];</b></div><br>
   Text string containing a date and version number for the library, in case 
   you want to display these somewhere.

<p><br>
<div class="al-api"><b>extern char <a name="allegro_error">allegro_error</a>[ALLEGRO_ERROR_SIZE];</b></div><br>
   Text string used by set_gfx_mode(), install_sound() and other functions to
   report error messages. If they fail and you want to tell the user why, this
   is the place to look for a description of the problem. Example:
<blockquote class="code"><pre>
      void abort_on_error(const char *message)
      {
         if (<a href="alleg009.html#screen" class="autotype" title="Global pointer to the screen hardware video memory.">screen</a> != NULL)
            <a href="alleg008.html#set_gfx_mode" class="autotype" title="Sets a graphic video mode.">set_gfx_mode</a>(GFX_TEXT, 0, 0, 0, 0);

         <a href="#allegro_message" class="autotype" title="Used mainly to show error messages to users.">allegro_message</a>("%s.\nLast Allegro error `%s'\n",
                         message, <a href="#allegro_error" class="autotype" title="Stores the last Allegro error message.">allegro_error</a>);
         exit(-1);
      }
      ...
         if (some_allegro_function() == ERROR_CODE)
            abort_on_error("Error calling some function!");</pre></blockquote>

<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="alleg008.html#set_gfx_mode" title="Sets a graphic video mode.">set_gfx_mode</a>,
<a class="xref" href="alleg024.html#install_sound" title="Initialises the sound module.">install_sound</a>.</blockquote>

<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg045.html#Available Allegro examples" title="">Available Allegro examples</a>.</blockquote>
<div class="al-api"><b>#define <a name="ALLEGRO_VERSION">ALLEGRO_VERSION</a></b></div><br>
   Defined to the major version of Allegro. From a version number like
   4.1.16, this would be defined to the integer 4.
   
<p><br>
<div class="al-api"><b>#define <a name="ALLEGRO_SUB_VERSION">ALLEGRO_SUB_VERSION</a></b></div><br>
   Defined to the middle version of Allegro. From a version number like
   4.1.16, this would be defined to the integer 1.
   
<p><br>
<div class="al-api"><b>#define <a name="ALLEGRO_WIP_VERSION">ALLEGRO_WIP_VERSION</a></b></div><br>
   Defined to the minor version of Allegro. From a version number like
   4.1.16, this would be defined to the integer 16.
   
<p><br>
<div class="al-api"><b>#define <a name="ALLEGRO_VERSION_STR">ALLEGRO_VERSION_STR</a></b></div><br>
   Defined to a text string containing all version numbers and maybe some
   additional text. This could be `4.2.1 (SVN)' for an Allegro version
   obtained straight from the SVN repository.
   
<p><br>
<div class="al-api"><b>#define <a name="ALLEGRO_DATE_STR">ALLEGRO_DATE_STR</a></b></div><br>
   Defined to a text string containing the year this version of Allegro was
   released, like <tt>`2004'</tt>.
   
<p><br>
<div class="al-api"><b>#define <a name="ALLEGRO_DATE">ALLEGRO_DATE</a></b></div><br>
   Defined to an integer containing the release date of Allegro in the packed
   format <tt>`yyyymmdd'</tt>. Example:
<blockquote class="code"><pre>
      const int year = <a href="#ALLEGRO_DATE" class="autotype" title="Defined to a number with the release date of Allegro.">ALLEGRO_DATE</a> / 10000;
      const int month = (<a href="#ALLEGRO_DATE" class="autotype" title="Defined to a number with the release date of Allegro.">ALLEGRO_DATE</a> / 100) % 100;
      const int day = <a href="#ALLEGRO_DATE" class="autotype" title="Defined to a number with the release date of Allegro.">ALLEGRO_DATE</a> % 100;

      <a href="#allegro_message" class="autotype" title="Used mainly to show error messages to users.">allegro_message</a>("Year %d, month %d, day %d\n",
         year, month, day);</pre></blockquote>

<p><br>
<div class="al-api"><b>Macro <a name="AL_ID">AL_ID</a>(a,b,c,d)</b></div><br>
   This macro can be used to create a packed 32 bit integer from 8 bit
   characters, on both 32 and 64 bit machines. These can be used for various 
   things, like custom datafile objects or system IDs. Example:
<blockquote class="code"><pre>
      #define OSTYPE_LINUX       <a href="#AL_ID" class="autotype" title="Converts four 8 bit values to a packed 32 bit integer ID.">AL_ID</a>('T','U','X',' ')</pre></blockquote>


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="alleg031.html#DAT_ID" title="Makes an ID value from four letters.">DAT_ID</a>.</blockquote>
<div class="al-api"><b>Macro <a name="MAKE_VERSION">MAKE_VERSION</a>(a, b, c)</b></div><br>
   This macro can be used to check if some Allegro version is (binary)
   compatible with the current version. It is safe to use &gt; and &lt; to
   check if one version is more recent than another.
   The third number is ignored if the second number is even, so
   MAKE_VERSION(4, 2, 0) is equivalent to MAKE_VERSION(4, 2, 1).
   This is because of our version numbering policy since 4.0.0:
   the second number is even for stable releases, which must be
   ABI-compatible with earlier versions of the same series.
   This macro is mainly useful for addon packages and libraries. See the 
   `ABI compatibility information' section of the manual for more detailed 
   information. Example:
<blockquote class="code"><pre>
      /* Check if the current version is compatible with Allegro 4.2.0 */
      #if (<a href="#MAKE_VERSION" class="autotype" title="Create a 32 bit integer from the Allegro version">MAKE_VERSION</a>(4, 2, 0) &lt;= <a href="#MAKE_VERSION" class="autotype" title="Create a 32 bit integer from the Allegro version">MAKE_VERSION</a>(<a href="#ALLEGRO_VERSION" class="autotype" title="Defined to the major version of Allegro.">ALLEGRO_VERSION</a>, \
                         <a href="#ALLEGRO_SUB_VERSION" class="autotype" title="Defined to the middle version of Allegro.">ALLEGRO_SUB_VERSION</a>, <a href="#ALLEGRO_WIP_VERSION" class="autotype" title="Defined to the minor version of Allegro.">ALLEGRO_WIP_VERSION</a>))
         /* Allegro 4.2.0 compatibility */
      #else
         /* Work-around */
      #endif</pre></blockquote>
   

<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#ALLEGRO_VERSION" title="Defined to the major version of Allegro.">ALLEGRO_VERSION</a>,
<a class="xref" href="#ALLEGRO_SUB_VERSION" title="Defined to the middle version of Allegro.">ALLEGRO_SUB_VERSION</a>,
<a class="xref" href="#ALLEGRO_WIP_VERSION" title="Defined to the minor version of Allegro.">ALLEGRO_WIP_VERSION</a>.</blockquote>
<div class="al-api"><b>extern int <a name="os_type">os_type</a>;</b></div><br>
   Set by allegro_init() to one of the values:
<blockquote class="text"><pre>
      OSTYPE_UNKNOWN    - unknown, or regular MSDOS
      OSTYPE_WIN3       - Windows 3.1 or earlier
      OSTYPE_WIN95      - Windows 95
      OSTYPE_WIN98      - Windows 98
      OSTYPE_WINME      - Windows ME
      OSTYPE_WINNT      - Windows NT
      OSTYPE_WIN2000    - Windows 2000
      OSTYPE_WINXP      - Windows XP
      OSTYPE_WIN2003    - Windows 2003
      OSTYPE_WINVISTA   - Windows Vista
      OSTYPE_OS2        - OS/2
      OSTYPE_WARP       - OS/2 Warp 3
      OSTYPE_DOSEMU     - Linux DOSEMU
      OSTYPE_OPENDOS    - Caldera OpenDOS
      OSTYPE_LINUX      - Linux
      OSTYPE_SUNOS      - SunOS/Solaris
      OSTYPE_FREEBSD    - FreeBSD
      OSTYPE_NETBSD     - NetBSD
      OSTYPE_IRIX       - IRIX
      OSTYPE_DARWIN     - Darwin
      OSTYPE_QNX        - QNX
      OSTYPE_UNIX       - Unknown Unix variant
      OSTYPE_BEOS       - BeOS
      OSTYPE_MACOS      - MacOS
      OSTYPE_MACOSX     - MacOS X</pre></blockquote>


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#allegro_init" title="Macro to initialise the Allegro library.">allegro_init</a>,
<a class="xref" href="#os_version" title="Version of the OS currently running.">os_version</a>,
<a class="xref" href="#os_multitasking" title="Indicates if the OS is multitasking.">os_multitasking</a>.</blockquote>
<div class="al-api"><b>extern int <a name="os_version">os_version</a>;</b></div><br>
<div class="al-api-cont"><b>extern int <a name="os_revision">os_revision</a>;</b></div><br>
   The major and minor version of the Operating System currently running.
   Set by allegro_init(). If Allegro for some reason was not able to
   retrieve the version of the Operating System, os_version and
   os_revision will be set to -1. For example: Under Win98 SE (v4.10.2222)
   os_version will be set to 4 and os_revision to 10.


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#os_type" title="Stores the detected type of the OS.">os_type</a>,
<a class="xref" href="#os_multitasking" title="Indicates if the OS is multitasking.">os_multitasking</a>.</blockquote>
<div class="al-api"><b>extern int <a name="os_multitasking">os_multitasking</a>;</b></div><br>
   Set by allegro_init() to either TRUE or FALSE depending on whether your
   Operating System is multitasking or not.


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#os_type" title="Stores the detected type of the OS.">os_type</a>,
<a class="xref" href="#os_version" title="Version of the OS currently running.">os_version</a>.</blockquote>
<div class="al-api"><b>void <a name="allegro_message">allegro_message</a>(const char *text_format, ...);</b></div><br>
   Outputs a message, using a printf() format string. Usually you want to
   use this to report messages to the user in an OS independent way when some
   Allegro subsystem cannot be initialised. But you must not use this function
   if you are in a graphic mode, only before calling set_gfx_mode(), or after
   a set_gfx_mode(GFX_TEXT). Also, this function depends on a system driver
   being installed, which means that it won't display the message at all on
   some platforms if Allegro has not been initialised correctly.

<p>
   On platforms featuring a windowing system, it will bring up a blocking GUI
   message box. If there is no windowing system, it will try to print the
   string to a text console, attempting to work around codepage differences
   by reducing any accented characters to 7-bit ASCII approximations.
   Example:
<blockquote class="code"><pre>
      if (<a href="#allegro_init" class="autotype" title="Macro to initialise the Allegro library.">allegro_init</a>() != 0)
         exit(1);

      if (init_my_data() != 0) {
         <a href="#allegro_message" class="autotype" title="Used mainly to show error messages to users.">allegro_message</a>("Sorry, missing game data!\n");
         exit(2);
      }</pre></blockquote>


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#allegro_init" title="Macro to initialise the Allegro library.">allegro_init</a>,
<a class="xref" href="#install_allegro" title="Initialise the Allegro library.">install_allegro</a>,
<a class="xref" href="alleg002.html#set_uformat" title="Set the global current text encoding format.">set_uformat</a>.</blockquote>

<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg045.html#Available Allegro examples" title="">Available Allegro examples</a>.</blockquote>
<div class="al-api"><b>void <a name="set_window_title">set_window_title</a>(const char *name);</b></div><br>
   On platforms that are capable of it, this routine alters the window title 
   for your Allegro program. Note that Allegro cannot set the window title 
   when running in a DOS box under Windows. Example:
<blockquote class="code"><pre>
      <a href="#set_window_title" class="autotype" title="Sets the window title of the Allegro program.">set_window_title</a>("Allegro rules!");</pre></blockquote>


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#set_close_button_callback" title="Handles the user clicking on the close button of the window.">set_close_button_callback</a>,
<a class="xref" href="alleg002.html#set_uformat" title="Set the global current text encoding format.">set_uformat</a>.</blockquote>

<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg045.html#exunicod" title="Using Unicode string functions.">exunicod</a>.</blockquote>
<div class="al-api"><b>int <a name="set_close_button_callback">set_close_button_callback</a>(void (*proc)(void));</b></div><br>
   On platforms that have a close button, this routine installs a callback 
   function to handle the close event. In other words, when the user clicks 
   the close button on your program's window or any equivalent device, the
   function you specify here will be called.

<p>
   This function should not generally attempt to exit the program or save 
   any data itself. The function could be called at any time, and there is 
   usually a risk of conflict with the main thread of the program. Instead, 
   you should set a flag during this function, and test it on a regular 
   basis in the main loop of the program.

<p>
   Pass NULL as the <tt>`proc'</tt> argument to this function to disable the close
   button functionality, which is the default state.

<p>
   Note that Allegro cannot intercept the close button of a DOS box in 
   Windows.
   
<p>
   Also note that the supplied callback is also called under MacOS X when
   the user hits Command-Q or selects "Quit" from the application menu.
   Example:
<blockquote class="code"><pre>
      volatile int close_button_pressed = FALSE;

      void close_button_handler(void)
      {
         close_button_pressed = TRUE;
      }
      <a href="alleg005.html#END_OF_FUNCTION" class="autotype" title="Locks the code used by a timer.">END_OF_FUNCTION</a>(close_button_handler)
      ...
      
      <a href="#allegro_init" class="autotype" title="Macro to initialise the Allegro library.">allegro_init</a>();
      <a href="alleg005.html#LOCK_FUNCTION" class="autotype" title="Locks the memory of a function used by a timer.">LOCK_FUNCTION</a>(close_button_handler);
      <a href="#set_close_button_callback" class="autotype" title="Handles the user clicking on the close button of the window.">set_close_button_callback</a>(close_button_handler);
      ...
         
      while (!close_button_pressed)
         do_stuff();</pre></blockquote>
<p><b>Return value:</b>
   Returns zero on success and non-zero on failure (e.g. the feature is not
   supported by the platform).


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#set_window_title" title="Sets the window title of the Allegro program.">set_window_title</a>.</blockquote>
<div class="al-api"><b>int <a name="desktop_color_depth">desktop_color_depth</a>();</b></div><br>
   Finds out the currently selected desktop color depth. You can use this
   information to make your program use the same color depth as the desktop,
   which will likely make it run faster because the graphic driver won't be
   doing unnecessary color conversions behind your back.

<p>
   Under some OSes, switching to a full screen graphics mode may automatically
   change the desktop color depth. You have, therefore, to call this function
   before setting any graphics mode in order to retrieve the real desktop
   color depth. Example:
<blockquote class="code"><pre>
      <a href="#allegro_init" class="autotype" title="Macro to initialise the Allegro library.">allegro_init</a>();
      ...
      if ((depth = <a href="#desktop_color_depth" class="autotype" title="Finds out the desktop color depth.">desktop_color_depth</a>()) != 0) {
         <a href="alleg008.html#set_color_depth" class="autotype" title="Sets the global pixel color depth.">set_color_depth</a>(depth);
      }</pre></blockquote>
<p><b>Return value:</b>
   Returns the color depth or zero on platforms where this information is not
   available or does not apply.


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#get_desktop_resolution" title="Finds out the desktop resolution.">get_desktop_resolution</a>,
<a class="xref" href="alleg008.html#set_color_depth" title="Sets the global pixel color depth.">set_color_depth</a>,
<a class="xref" href="alleg008.html#set_gfx_mode" title="Sets a graphic video mode.">set_gfx_mode</a>.</blockquote>
<div class="al-api"><b>int <a name="get_desktop_resolution">get_desktop_resolution</a>(int *width, int *height);</b></div><br>
   Finds out the currently selected desktop resolution. You can use this
   information to avoid creating windows bigger than the current resolution.
   This is especially important for some windowed drivers which are unable
   to create windows bigger than the desktop. Each parameter is a pointer
   to an integer where one dimension of the screen will be stored.

<p>
   Under some OSes, switching to a full screen graphics mode may automatically
   change the desktop resolution. You have, therefore, to call this function
   before setting any graphics mode in order to retrieve the real desktop
   resolution. Example:
<blockquote class="code"><pre>
      int width, height;
      
      <a href="#allegro_init" class="autotype" title="Macro to initialise the Allegro library.">allegro_init</a>();
      ...
      if (<a href="#get_desktop_resolution" class="autotype" title="Finds out the desktop resolution.">get_desktop_resolution</a>(&amp;width, &amp;height) == 0) {
         /* Got the resolution correctly */
      }</pre></blockquote>
<p><b>Return value:</b>
   Returns zero on success, or a negative number if this information is not
   available or does not apply, in which case the values stored in the
   variables you provided for <tt>`width'</tt> and <tt>`height'</tt> are undefined.


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#desktop_color_depth" title="Finds out the desktop color depth.">desktop_color_depth</a>,
<a class="xref" href="alleg008.html#set_gfx_mode" title="Sets a graphic video mode.">set_gfx_mode</a>.</blockquote>
<div class="al-api"><b>void <a name="check_cpu">check_cpu</a>();</b></div><br>
   Detects the CPU type, setting the following global variables. You don't 
   normally need to call this, because allegro_init() will do it for you.


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#cpu_vendor" title="Contains the CPU vendor name.">cpu_vendor</a>,
<a class="xref" href="#cpu_family" title="Contains the CPU type.">cpu_family</a>,
<a class="xref" href="#cpu_model" title="Contains the Intel CPU submodel.">cpu_model</a>,
<a class="xref" href="#cpu_capabilities" title="Contains the capability flags of the CPU.">cpu_capabilities</a>,
<a class="xref" href="#allegro_init" title="Macro to initialise the Allegro library.">allegro_init</a>.</blockquote>
<div class="al-api"><b>extern char <a name="cpu_vendor">cpu_vendor</a>[];</b></div><br>
   On Intel PCs, contains the CPU vendor name if known. On Mac OSX systems 
   this contains the PPC subtype name. On other platforms, this may be an empty
   string. You can read this variable after you have called check_cpu()
   (which is automatically called by allegro_init()).


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#check_cpu" title="Detects the CPU type.">check_cpu</a>,
<a class="xref" href="#cpu_family" title="Contains the CPU type.">cpu_family</a>,
<a class="xref" href="#cpu_model" title="Contains the Intel CPU submodel.">cpu_model</a>,
<a class="xref" href="#cpu_capabilities" title="Contains the capability flags of the CPU.">cpu_capabilities</a>,
<a class="xref" href="#allegro_init" title="Macro to initialise the Allegro library.">allegro_init</a>.</blockquote>
<div class="al-api"><b>extern int <a name="cpu_family">cpu_family</a>;</b></div><br>
   Contains the Intel type, where applicable. Allegro defines the following
   CPU family types:
<blockquote class="text"><pre>
      CPU_FAMILY_UNKNOWN  - The type of processor is unknown
      CPU_FAMILY_I386     - The processor is an Intel-compatible 386
      CPU_FAMILY_I486     - The processor is an Intel-compatible 486
      CPU_FAMILY_I586     - The processor is a Pentium or equivalent
      CPU_FAMILY_I686     - The processor is a Pentium Pro, II, III
                            or equivalent
      CPU_FAMILY_ITANIUM  - The processor is an Itanium processor
      CPU_FAMILY_POWERPC  - The processor is a PowerPC processor
      CPU_FAMILY_EXTENDED - The processor type needs to be read
                            from the cpu_model
</pre></blockquote>
   You can read this variable after you have called check_cpu()
   (which is automatically called by allegro_init()).


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#check_cpu" title="Detects the CPU type.">check_cpu</a>,
<a class="xref" href="#cpu_vendor" title="Contains the CPU vendor name.">cpu_vendor</a>,
<a class="xref" href="#cpu_model" title="Contains the Intel CPU submodel.">cpu_model</a>,
<a class="xref" href="#cpu_capabilities" title="Contains the capability flags of the CPU.">cpu_capabilities</a>,
<a class="xref" href="#allegro_init" title="Macro to initialise the Allegro library.">allegro_init</a>.</blockquote>
<div class="al-api"><b>extern int <a name="cpu_model">cpu_model</a>;</b></div><br>
   Contains the CPU submodel, where applicable. Allegro defines at least the 
   following CPU family types (see include/allegro/system.h for a more 
   complete list):
<blockquote class="text"><pre>
      CPU_FAMILY_I586:
         CPU_MODEL_PENTIUM, CPU_MODEL_K5, CPU_MODEL_K6

      CPU_FAMILY_I686:
         CPU_MODEL_PENTIUMPRO, CPU_MODEL_PENTIUMII,
         CPU_MODEL_PENTIUMIIIKATMAI, CPU_MODEL_PENTIUMIIICOPPERMINE,
         CPU_MODEL_ATHLON, CPU_MODEL_DURON

      CPU_FAMILY_EXTENDED:
         CPU_MODEL_PENTIUMIV, CPU_MODEL_XEON,
         CPU_MODEL_ATHLON64, CPU_MODEL_OPTERON

      CPU_FAMILY_POWERPC:
         CPU_MODEL_POWERPC_x, for x=601-604, 620, 750, 7400, 7450
</pre></blockquote>
   You can read this variable after you have called check_cpu() (which is 
   automatically called by allegro_init()). Make sure you check the cpu_family
   and cpu_vendor so you know which models make sense to check.


<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#check_cpu" title="Detects the CPU type.">check_cpu</a>,
<a class="xref" href="#cpu_vendor" title="Contains the CPU vendor name.">cpu_vendor</a>,
<a class="xref" href="#cpu_family" title="Contains the CPU type.">cpu_family</a>,
<a class="xref" href="#cpu_capabilities" title="Contains the capability flags of the CPU.">cpu_capabilities</a>,
<a class="xref" href="#allegro_init" title="Macro to initialise the Allegro library.">allegro_init</a>.</blockquote>
<div class="al-api"><b>extern int <a name="cpu_capabilities">cpu_capabilities</a>;</b></div><br>
   Contains CPU flags indicating what features are available on the current 
   CPU. The flags can be any combination of these:
<blockquote class="text"><pre>
      CPU_ID       - Indicates that the "cpuid" instruction is
                     available. If this is set, then all Allegro CPU
                     variables are 100% reliable, otherwise there
                     may be some mistakes.
      CPU_FPU      - An FPU is available.
      CPU_IA64     - Running on Intel 64 bit CPU
      CPU_AMD64    - Running on AMD 64 bit CPU
      CPU_MMX      - Intel MMX  instruction set is available.
      CPU_MMXPLUS  - Intel MMX+ instruction set is available.
      CPU_SSE      - Intel SSE  instruction set is available.
      CPU_SSE2     - Intel SSE2 instruction set is available.
      CPU_SSE3     - Intel SSE3 instruction set is available.
      CPU_3DNOW    - AMD 3DNow! instruction set is available.
      CPU_ENH3DNOW - AMD Enhanced 3DNow! instruction set is
                     available.
      CPU_CMOV     - Pentium Pro "cmov" instruction is available.
</pre></blockquote>
   You can check for multiple features by OR-ing the flags together.
   For example, to check if the CPU has an FPU and MMX instructions
   available, you'd do:
<blockquote class="code"><pre>
      if ((<a href="#cpu_capabilities" class="autotype" title="Contains the capability flags of the CPU.">cpu_capabilities</a> &amp; (CPU_FPU | CPU_MMX)) ==
          (CPU_FPU | CPU_MMX)) {
         printf("CPU has both an FPU and MMX instructions!\n");
      }
</pre></blockquote>
   You can read this variable after you have called check_cpu() (which is
   automatically called by allegro_init()).




<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#check_cpu" title="Detects the CPU type.">check_cpu</a>,
<a class="xref" href="#cpu_vendor" title="Contains the CPU vendor name.">cpu_vendor</a>,
<a class="xref" href="#cpu_family" title="Contains the CPU type.">cpu_family</a>,
<a class="xref" href="#cpu_model" title="Contains the Intel CPU submodel.">cpu_model</a>,
<a class="xref" href="#cpu_capabilities" title="Contains the capability flags of the CPU.">cpu_capabilities</a>,
<a class="xref" href="#allegro_init" title="Macro to initialise the Allegro library.">allegro_init</a>.</blockquote>
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