.. _xs1_data_types:

XS1 Data Types
--------------

The size and alignment of C and XC's data types are not specified by the
language. This allows the size of ``int`` to be set to the natural word
size of the target device, ensuring the fastest possible performance for
many computations. It also allows the alignment to be set wide enough to
enable efficient memory loads and stores. :ref:`xs1_data_types_table`
represents the size and alignment of the data types specified by the 
:ref:`xCORE Application Binary Interface <xs1_abi>`, which provides a standard interface for linking objects compiled from both C and XC. 

.. _xs1_data_types_table:

.. table:: Size and alignment of data types on XS1 devices

    +---------------+-----------+------------+-------------+-------------------+
    |               |           |            |Supported    |                   |
    |               |           |            +------+------+                   |
    |Data Type      |Size (bits)|Align (bits)|XC    |C     |Meaning            |
    +---------------+-----------+------------+------+------+-------------------+
    |``char``       |8          |8           |Y     |Y     |Character type     |
    +---------------+-----------+------------+------+------+-------------------+
    |``short``      |16         |16          |Y     |Y     |Short integer      |
    +---------------+-----------+------------+------+------+-------------------+
    |``int``        |32         |32          |Y     |Y     |Native integer     |
    +---------------+-----------+------------+------+------+-------------------+
    |``long``       |32         |32          |Y     |Y     |Long integer       |
    +---------------+-----------+------------+------+------+-------------------+
    |``long long``  |64         |32          |N     |Y     |Long long integer  |
    +---------------+-----------+------------+------+------+-------------------+
    |``float``      |32         |32          |N     |Y     |32-bit IEEE float  |
    +---------------+-----------+------------+------+------+-------------------+
    |``double``     |64         |32          |N     |Y     |64-bit IEEE float  |
    +---------------+-----------+------------+------+------+-------------------+
    |``long double``|64         |32          |N     |Y     |64-bit IEEE float  |
    +---------------+-----------+------------+------+------+-------------------+
    |``void *``     |32         |32          |N     |Y     |Data pointer       |
    +---------------+-----------+------------+------+------+-------------------+
    |``port``       |32         |32          |Y     |N     |Port               |
    +---------------+-----------+------------+------+------+-------------------+
    |``timer``      |32         |32          |Y     |N     |Timer              |
    +---------------+-----------+------------+------+------+-------------------+
    |``chanend``    |32         |32          |Y     |N     |Channel end        |
    +---------------+-----------+------------+------+------+-------------------+

In addition:

-  The ``char`` type is by default unsigned.
-  The types ``char``, ``short`` and ``int`` may be specified in a
   bit-field's declaration.
-  A zero-width bit-field forces padding until the next bit-offset
   aligned with the bit-field's declared type.
-  The notional transfer type of a port is ``unsigned int`` (32 bits).
-  The notional counter type of a port is ``unsigned short`` (16 bits).
-  The notional counter type of a timer is ``unsigned int`` (32 bits).