Many parameters and data values are recorded in the C3D file as 16-bit integer values.  In the original C3D implementation, integer values in C3D files were always stored as one’s complement 16-bit signed integers; INTEGER*2 in FORTRAN terms, that is numbers in the range of –32767 to +32767.

However, in many cases, the use of signed integers and bytes reduces the range available for parameter and data storage – as a result, it is common to find unsigned integers and bytes used in many C3D files yielding numerical ranges from 0 to +65535 for unsigned 16-bit integers.

One’s complement signed Integers (–32767 to +32767) remain the default storage format for analog data and parameters associated with signed analog data.