Yes, I get it. According to this Ascii UTF-8 table: https :// kellykjones.tripod.com/webtools/ascii_utf8_table.html

0x90 is becoming 0xC2 0x90
0xFF is becoming 0xC3 0xBF

But anything below 0x80 (0x00 ~ 0x7F) is still one byte original value.

Input output library is not part of the standard, or independent from the C language. Each system and platform are free to implement thier own way.
As some already pointed out, the way data stored is depends on Endian , and also the size of the variable. 16bits, 32bits and 64bits platform will have different result.