Final answer:
The question pertains to writing a MIPS assembly program that converts an ASCII number string to an integer. The program loops through the string, constructs the number by continuously multiplying by ten and adding each digit, and accounts for non-digit characters by setting an error code.
Step-by-step explanation:
To write a MIPS assembly program that converts a null-terminated ASCII string representing an integer to its numeric equivalent, you need to follow several steps. First, you'll initialize your register to store the final value and a temporary register to store each digit. Then, you will use a loop to go through each character of the string, convert it from ASCII to its digit value, handle the negative sign if necessary, and construct the number by multiplying the current value by 10 and adding the new digit. You'll also check for non-digit characters and terminate if one is found. When a null character is reached, the final integer is stored in register $v0, and the program ends.
Here is an outline of the MIPS code:
# Assume $a0 has the address of the string
main:
li $v0, 0 # Store the result here - Assume positive number
li $t1, 10 # Multiplier for the position value
byteToIntLoop:
lb $t0, 0($a0) # Load byte
beq $t0, 0, endLoop # Break if null-terminator
blt $t0, '0', error # If less than ASCII '0' then error
bgt $t0, '9', error # If greater than ASCII '9' then error
sub $t0, $t0, '0' # Convert ASCII to integer
mul $v0, $v0, $t1 # Multiply current value by 10
add $v0, $v0, $t0 # Add new digit
addi $a0, $a0, 1 # Move to the next character
j byteToIntLoop
error:
li $v0, 1 # Set error code
endLoop:
The loop continues until it finds a null character, at which point the constructed integer in $v0 will contain the final value. If a non-digit character is encountered, it jumps to the error label, where $v0 is set to 1. The above code does not handle negative numbers; additional logic would be required to support that.