These services are invoked via the syscall pseudo-instruction after storing the service code in the register $v0.

Service	Code	Arguments	Result
print_int	1	$a0 = integer
print_float	2	$f12 = float
print_double	3	$f12 = double
print_string	4	$a0 = char *
read_int	5		integer in $v0
read_float	6		float in $f0
read_double	7		double in $f0
read_string	8	$a0 = buffer, $a1 = length	string in buffer (including "\n\0")
print_char	11	$a0 = char
read_char	12		char in $v0