a+b-c digits

section .data
    prompt1 db "Enter A: "
    prompt1_len equ $ - prompt1
    prompt2 db "Enter B: "
    prompt2_len equ $ - prompt2
    prompt3 db "Enter C: "
    prompt3_len equ $ - prompt3
    result_msg db "Result (A+B-C): "
    result_msg_len equ $ - result_msg
    newline db 10

    STDIN_FILENO  equ 0
    STDOUT_FILENO equ 1
    STDERR_FILENO equ 2

section .bss
    num1 resb 2    ; Space for digit A and newline
    num2 resb 2    ; Space for digit B and newline
    num3 resb 2    ; Space for digit C and newline
    result resb 2  ; Space for result and newline

section .text
    global _start

_start:
    ; Print "Enter A: "
    mov rax, 1          ; sys_write
    mov rdi, 1          ; stdout
    mov rsi, prompt1
    mov rdx, prompt1_len
    syscall

    ; Read A
    mov rax, 0          ; sys_read
    mov rdi, 0          ; stdin
    mov rsi, num1
    mov rdx, 2          ; read 2 bytes (digit + newline)
    syscall

    ; Print "Enter B: "
    mov rax, 1
    mov rdi, 1
    mov rsi, prompt2
    mov rdx, prompt2_len
    syscall

    ; Read B
    mov rax, 0
    mov rdi, 0
    mov rsi, num2
    mov rdx, 2
    syscall

    ; Print "Enter C: "
    mov rax, 1
    mov rdi, 1
    mov rsi, prompt3
    mov rdx, prompt3_len
    syscall

    ; Read C
    mov rax, 0
    mov rdi, 0
    mov rsi, num3
    mov rdx, 2
    syscall

    ;  A+B-C
    mov al, [num1]
    sub al, '0'         ;  ASCII -> number
    mov bl, [num2]
    sub bl, '0'         ; ASCII -> number
    add al, bl          ; A + B
    mov bl, [num3]      ; Get third digit
    sub bl, '0'         ; ASCII -> number
    sub al, bl          ; (A + B) - C
    add al, '0'         ; back to ASCII

    ; Store result
    mov [result], al

    ; Print result message
    mov rax, 1
    mov rdi, 1
    mov rsi, result_msg
    mov rdx, result_msg_len
    syscall

    ; Print result
    mov rax, 1
    mov rdi, 1
    mov rsi, result
    mov rdx, 1
    syscall

    ; Print newline
    mov rax, 1
    mov rdi, 1
    mov rsi, newline
    mov rdx, 1
    syscall

    ; Exit program
    mov rax, 60         ; sys_exit
    mov rdi, 0          ; exit code 0
    syscall