Can you use multiple BEQ statements in MIPS?

Question

I am trying to write a code which takes a,b,c or d as user input then branches them depending on what the user wants to. For some reason when I pick one of the 4 options the code just falls through all the branches and the program ends. Is it because there can only be one branch statement used?

.data
    #messages
    options: .asciiz "\nPlease enter a, b, c or d: "
    youEntered: .asciiz "\nYou picked: "
    bmiMessage: .asciiz "\nThis is the BMI Calculator!"
    tempMessage: .asciiz "\nThis converts Farenheit to Celcius!"
    weightMessage: .asciiz "\nThis converts Pounds to Kilograms!"
    sumMessage: .asciiz "\nThis is the sum calculator!"
    repeatMessage: .asciiz "\nThat was not a, b, c or d!"
    
    #variables
    input: .space   4 #only takes in one character
    
.text
main:
    #display "options" messsage
    li $v0, 4
    la $a0, options
    syscall
    
    #user input 
    li $v0, 8
    la $a0, input
    li $a1, 4
    syscall

    #display "youEntered" messsage
    li $v0, 4
    la $a0, youEntered
    syscall

    #display option picked
    li $v0, 4
    la $a0, input
    syscall

#branching
beq $a0, 'a', bmi
beq $a0, 'b', temperature
beq $a0, 'c', weight
beq $a0, 'd', sum


#end of main
li $v0, 10
syscall

bmi: 
    li $v0, 4
    la $a0, bmiMessage
    syscall

temperature:
    li $v0, 4
    la $a0, tempMessage
    syscall
    
weight: 
    li $v0, 4
    la $a0, weightMessage
    syscall
    
sum: 
    li $v0, 4
    la $a0, sumMessage
    syscall

repeat: 
    li $v0, 4
    la $a0, repeatMessage
    syscall

Anything will be helpful Thanks guys!

Answer 1

When you have code like:

label:
    # some code

another_label:
    # some more code

after # some code executes, control just continues on to # some more code. You probably want to jump unconditionally to your end of main code:

label:
    # some code
    j done

another_label:
    # some more code
    j done

# ...

done:
    # end of main

This, coupled with your branches, gives exclusive block semantics like a C if-else chain:

if (something) {
   // do something
}
else if (something_else) {
   // do something else
}

// end of main

Secondly, $a0 is an address, not a value, so the branch comparisons will fail. Try loading the value located at the address into a register, then using the register value to compare against 'a', 'b' and so on.

For example,

lb $t0, input
beq $t0, 'a', bmi
beq $t0, 'b', temperature
beq $t0, 'c', weight
beq $t0, 'd', sum