You can take Implement factorial using MIPS a look before doing this. This was my college's computer organization assignment. I implemented a Fibonacci using the following algorithm:

In MIPS, I use `$a0`

as the parameter *n* of *F(n)*. For example, letting `$a0`

equal to `10`

and jumping to the `fib`

label means *F(10)*, and at the end of the recursion, the result will be stored in `$v0`

.

```
main:
addi $a0, $zero, 10 # let the parameter n be 10
jal fib # jump to fib label, i.e. calling F(10)
j exit
fib:
addi $sp, $sp, -8 # allocate 8 bytes to this stack
sw $ra, 0($sp) # save the address of the instruction that calls fib label (instruction address)
sw $a0, 4($sp) # save the value of n
slti $t0, $a0, 2 # $t0 is used for conditions. If n < 2 then $t0 = 1, else $t0 = 0
beq $t0, $zero, L1 # if $t0 == 0 then jump to branch L1
add $v0, $v0, $a0 # let $v0 add n
addi $sp, $sp, 8 # let $sp point to upper stack
jr $ra # jump to the next line of the line calling fib
L1:
addi $a0, $a0, -1 # n = n - 1
jal fib # jump to fib label again, like as calling F(n - 1)
addi $a0, $a0, -1 # n = n - 1
jal fib # jump to fib label again, like as calling F(n - 2)
lw $a0, 4($sp) # recover the value of n
lw $ra, 0($sp) # recover instruction address
addi, $sp, $sp, 8 # let $sp point to upper stack
jr $ra # jump to the next line of the line calling L1
exit:
```

The execution result of the MARS simulator looks like this:

You can see that the value of `$v0`

is `0x37`

, 55 in decimal, which is the result of *F(10)*.

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