MATLAB Programming

Using Low-Level File I/O Functions
Controlling the Number of Values Read
fread accepts an optional second argument that controls the number of
values read (if unspecified, the default is the entire file). For example, this
statement reads the first 100 data values of the file specified by fid into
the column vector A.
A = fread(fid,100);
Replacing the number 100 with the matrix dimensions [10 10] reads the
same 100 elements into a 10-by-10 array.
Controlling the Data Type of Each Value
An optional third argument to fread controls the data type of the input. The
data type argument controls both the number of bits read for each value and
the interpretation of those bits as character, integer, or floating-point values.
MATLAB supports a wide range of precisions, which you can specify with
MATLAB specific strings or their C or Fortran equivalents.
Some common precisions include
• 'char' and 'uchar' for signed and unsigned characters (usually 8 bits)
• 'short' and 'long' for short and long integers (usually 16 and 32 bits,
respectively)
• 'float' and 'double' for single- and double-precision floating-point
values (usually 32 and 64 bits, respectively)
Note The meaning of a given precision can vary across different hardware
platforms. For example, a 'uchar' is not always 8 bits. fread also provides
a number of more specific precisions, such as 'int8' and 'float32'. If
in doubt, use precisions that are not platform dependent. See fread for
a complete list of precisions.
For example, if fid refers to an open file containing single-precision
floating-point values, then the following command reads the next 10
floating-point values into a column vector A:
A = fread(fid,10,'float');
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