OS_WriteC - Write char. in R0
OS_WriteS - In-line string
OS_Write0 - Write null-terminated string (R0 in points to string, R0 out to zero byte
OS_WriteN - Counted string (R0 in pointer to string, R1 = length)
OS_WriteI - Add ASCII to SWI number
OS_NewLine
OS_PrettyPrint - <13> newline, <9> Tab to next 8 char. col., <31> hard space
R0 = string pointer (Zero-terminated)