guchar
From Just Solve the File Format Problem
guchar is exactly the same as the C language unsigned char data type; it is included in GLib for completeness. This consists of a single 8-bit byte which unambiguously represents a number (or character code point) from 0 to 255; usually the regular char (or gchar) does too, but that could also be construed as a signed number from -128 to 127.