Mips div.s syntax error

I am using QtSpim 9.9.1 to write my Computer Architecture course homework i had a syntax error when use div.s operator but it's OK when I use div. Another error appears when try to get float from user but it also disappears when get integer. Here is my code :

.text
    main:
        # Print "This program solves an equation of style a*x + c = 0, print out the result on console."
        la $a0, hello_msg           # load the address of hello_msg into $a0.
        li $v0, 4                       # 4 is the print_string syscall.
        syscall                         # do the syscall.

        # Print "Enter (a) value please :"
        la $a0, enter_a_msg         # load the address of enter_a_msg into $a0.
        li $v0, 4                       # 4 is the print_string syscall.
        syscall                         # do the syscall.

        ## Get (a) from user, put into $t0.
        li $v0, 6                       # load syscall read_float into $v0.
        syscall                         # make the syscall.
        move $t0, $f0               # move the number read into $t0.////////here got error//////

        # Print "Enter (c) value please :"
        la $a0, enter_c_msg         # load the address of enter_c_msg into $a0.
        li $v0, 4                       # 4 is the print_string syscall.
        syscall                         # do the syscall.

        ## Get (c) from user, put into $t1.
        li $v0, 6                       # load syscall read_float into $v0.
        syscall                         # make the syscall.
        move $t1, $f0               # move the number read into $t1.///////also here 

        # Compute (x), put into $t2.
        neg $t3, $t1                    # get -c into $t3.
        div.s $t2, $t3, $t0             # get x = -c / a into $t2.//// also here Error


        # Print "Value of (x) is :"
        la $a0, result_msg      # load the address of result_msg into $a0.
        li $v0, 4                       # 4 is the print_string syscall.
        syscall                         # do the syscall.

        # Print (x) value .
        move $a0, $t2               # move (x) value into $a0.
        li $v0, 1                       # load syscall print_int into $v0.
        syscall                         # make the syscall.

        li $v0, 10                      # 10 is the exit syscall.
        syscall                         # do the syscall.

# Data for the program:
.data
    hello_msg:      .asciiz "This program solves an equation of style a*x + c = 0,\nprints out the result on console.\n"
    enter_a_msg:    .asciiz "Enter (a) value please :"
    enter_c_msg:    .asciiz "Enter (c) value please :"
    result_msg:     .asciiz "Value of (x) is :"

# end Equation.asm

Solution

move $t0, $f0

To convert a floating-point register to an integer and move it to a general-purpose register you should use something like this:

cvt.w.s $f0, $f0
mfc1 $t0, $f0

If you wanted to move $f0 to another floating-point register you should use e.g.:

mov.s $f1,$f0

div.s $t2, $t3, $t0

div.s works with floating-point registers ($f0-$f31), not with the general-purpose registers ($an, $tn, $vn and so on). Refer to the MIPS floating-point instruction set list.