Reading and Printing SPIM provides a small set of operating system-like services through the system call instruction, named syscall. To request a service, a program loads the system call code (it can be found in MIPS System calls uploaded in the Useful Resources folder in Sakai) into register $v0 and arguments into register file registers $a0-$a3 (or $f12 for floating-point values). System calls that return values put their results in the register $v0 (or $f0 for floating-point results) [1] Reading and printing operations can be done with syscall. In order to become familiar with syscall, read the following example first. # Registers used: $to -used to hold the first number # t1 - used to hold the second number # $t2 - used to hold the difference of the contents of $t1 and $to # $v0 - syscall parameter and return value # $a0 - syscall argument . text main: ## Get first number from the user, store it into $to li $v0, 5 syscall move $to, $v # load syscall read-int into $v0 make the syscall. # move the number read into Sto ## Get second number from the user, put into $t1 li $v0, 5 # load syscall read-int into $v0 syscall # make the syscall move $t1, $v0 # move the number read into register $t1 In this example, the syscall instruction is first used to read input. The system code for this operation is 5. Then we use system code 1 to print this input. Notice that we also use code 10 to terminate the program