Many parameters and data values are recorded in the C3D file as integer values.  In the original C3D implementation, all 8-bit byte values were signed bytes with a range of –127 to +127.

However, in some cases, the use of signed bytes limited the range available for parameter storage – as a result, it is common to find unsigned bytes used in many C3D files yielding numerical ranges from 0 +255 for an unsigned 8-bit byte counter. Note that this does not apply to the bytes defining the group and parameter name lengths which are stored and read as signed bytes to record the locked, or unlocked, status flag.