Exception Handler Services

Here are the services of the SPIM exception handler. The following pages explain how to use them. The print services write characters to the simulated monitor of SPIM. The read services read characters from the keyboard and (for numeric read services) convert character strings into the appropriate type.

Service	Code in $v0	Arguments	Returned Value
print integer	1	$a0 `==` integer
print float	2	$f12 `==` float
print double	3	($f12, $f13) `==` double
print string	4	$a0 `==` address of string
read integer	5		$v0 `==` integer
read float	6		$f0 `==` float
read double	7		($f0, $f1) `==` double
read string	8	$a0 `==` buffer address $a1 `==` buffer length
allocate memory	9	$a0 `==` number of bytes	$v0 `==` address
exit	10

Here is an example of how to use a service. Load register $v0 with the code for the exit service and then use the syscall instruction. The exit service stops the program. (Until now we have been single stepping the program or crashing into the bytes beyond the end of the program).

li      $v0,10      # code 10 == exit
syscall             # Return control to the
                    # operating system.

Answer:

Exception Handler Services

QUESTION 3: