void g(char c, signed char sc, unsigned char uc)
{
    c = 255; //implementation-defined if plain chars are signed and have 8 bits
    c = sc; //OK
    c = uc; //implementation-defined if plain chars are signed and if uc's value is too large
    sc = uc; //implementation-defined if uc's value is too large
    uc = sc; //OK: conversion to unsigned
    sc = c; //implementation-defined if plain chars are unsigned and if c's value is too large
    uc = c; //OK: conversion to unsigned
}

signed char sc = -160;
unsigned char uc = sc; //uc == 116 (because 256-160==116)
cout << uc; //print 't'