MIPS中的Pascal三角形

Question

I need some serious help in MIPS assembly. This program is supposed to do two things. Those two things are:

1. Compute C(n,k) = n!/((nk)!k!)

Input: spim -f 90.s 4 6

output:
6 4
720 24
15

2.Display Row n of Pascal's Triangle for k = 0 to n
Input: Same as before (spim -f 90.s 4 6)

Output: 6 4 720 24 15 1 6 15 20 15 6 1 (This is what the final input should be.)

I basically need write a function displayRow that displays row n of Pascal's triangle for k = 0 to n. Ignore the value for k that is passed in. Since the displayRow function calls Cnk, you I must contruct a stack frame. Within displayRow I need to write a loop that goes from k=0 to n. Within the body of the loop display the return value for Cnk(n,k). I'm stuck and my output looks like this:

spim: (parser) parse error on line 174 of file 90.s bgtz $v0 The following symbols are undefined: atoi

6 4 720 24 24

I do not know where to go from here. Some serious help would be greatly appreciated! Here is my code....

     # Display Row n of Pascal's Triangle for k=0 to n
     # usage: spim -f 90.s 4 6

    .data
    newline: .asciiz "\n"
    space: .asciiz " "

    .text
    .globl main

    main:
    # hard coded
    li $t0 6
    li $t1 4

    # grab command line stuff - a0 is arg count and a1 points to list of args
    move $s0 $a0
    move $s1 $a1

    # zero out these registers just to be safe
    move $s2 $zero
    move $s3 $zero
    move $s4 $zero

    # check if less than three arguments are given
    li $t3 2
    blt $a0 $t3 default
    bgt $a0 $t3 default

    # parse the first number
    lw $a0 4($s1)
    jal atoi
    move $s2 $v0

    # parse the second number
    lw $a0 8($s1)
    jal atoi
    move $s3 $v0

    # load a0 and a1 with two integers
    move $a0 $s2
    move $a1 $s3

    move $t0, $a0
    move $t1, $a1


    # swap if n < k
    slt $t3 $t0 $t1
    beq $t3 $0 done
    move $t2 $t0
    move $t0 $t1
    move $t1 $t2

    done:
    # move the result from t0 to v0 to print it
    move $a0 $t0
    li $v0 1
    syscall

    la $a0 space
    li $v0 4
    syscall

    move $a0 $t1
    li $v0 1
    syscall

    la $a0 newline
    li $v0 4
    syscall

    move $t8 $t0
    jal factorial

    move $a0 $t9
    li $v0 1
    syscall
    move $s2 $t9

    la $a0 space
    li $v0 4
    syscall

    move $t8 $t1
    jal factorial

    move $a0 $t9
    li $v0 1
    syscall
    move $s3 $t9

    la $a0 newline
    li $v0 4
    syscall

    move $a0 $s3
    li $v0 1
    syscall

    la $a0 newline
    li $v0 4
    syscall

    li $v0 10  # 10=exit
    syscall

    default:
    move $a0 $t0
    move $a1 $t1
    j done

    pascal:
    addi $sp, $sp, -16             # create stack frame
    sw $ra, 12($sp)                # save return address
    sw $s0, 8($sp)                 # save three registers
    sw $s1, 4($sp)
    sw $s2, 0($sp)

    beq $a1, $zero, one            # branch if col == 0
    beq $a1, $a0, one              # branch if col == row

    add $s0, $a0, $zero            # save argument values
    add $s1, $a1, $zero
    addi $a0, $a0, -1              # compute args for first recursion
    addi $a1, $a1, -1
    jal pascal                     # pascal(row-1, col-1)
    add $s2, $v0, $zero            # save returned value

    addi $a0, $s0, -1              # compute args for second recursion
    add $a1, $s1, $zero
    jal pascal                     # pascal(row-1, col)
    add $v0, $v0, $s2              # add the two values

    #done:
    lw $ra, 12($sp)                # restore registers
    lw $s0, 8($sp)
    lw $s1, 4($sp)
    lw $s2, 0($sp)
    addi $sp, $sp, 16
    jr $ra                         # return

    one:
    addi $v0, $zero, 1 # return constant 1
    j done

    #---------------------Factorial
    factorial:
    li $t9 1

    fac:
    beqz $t8 return
    mul $t9 $t9 $t8
    addi $t8 $t8 -1
    j fac

    return:
    move $v0 $t8
    jr $ra

    #---------------
    Cnk:
    addi $sp, $sp, -32  # Stack frame is 32 bytes long
    sw   $ra, 20($sp)   # Save return address
    sw   $fp, 16($sp)   # Save frame pointer
    addi $fp, $sp, 28   # Set up frame pointer
    sw   $a0, 0($fp)    # Save argument (n)

    lw $v0 0($fp)
    bgtz $v0
    # --------- ATOI FUNCTION
    atoi:
    move $v0, $zero

    # detect sign
    li $t0, 1
    lbu $t1, 0($a0)
    bne $t1, 45, digit
    li $t0, -1
    addu $a0, $a0, 1

    digit:
    # read character
    lbu $t1, 0($a0)

    # finish when non-digit encountered
    bltu $t1, 48, finish
    bgtu $t1, 57, finish

    # translate character into digit
    subu $t1, $t1, 48

    # multiply the accumulator by ten
    li $t2, 10
    mult $v0, $t2
    mflo $v0

    # add digit to the accumulator
    add $v0, $v0, $t1

    # next character
    addu $a0, $a0, 1
    b digit

    finish:
    mult $v0, $t0
    mflo $v0
    jr $ra
    #----------------------------------------

Answer 1

The answer is in the error message:

spim: (parser) parse error on line 174 of file 90.s 
          bgtz $v0
                  ^ 
The following symbols are undefined: 
atoi

btgz requires a target and you have given none. Figure out where ou want it to branch to and assign the target.