Nios II custom instruction faster in 32bit or 128bit

Everything is just a number!

The C 'char' type is just a 8-bit number, you can think of the input/output as using base 256 where some of the values are impossible to type!

In C all arithmetic on types smaller than 'int' is done by converting the value to 'int', doing the maths, then masking off the high bits if the value is saved to a char variable. char is usually signed.

(This is probably because the pdp11 only had a sign-extending byte read!)

This means that 'unsigned char' gets promoted to 'int' (not 'unsigned int') unless 'sizeof (int) == 1'.