CSC231 Crash Course Solution 1

--D. Thiebaut 15:10, 4 March 2011 (EST)

---

;;; prog1.asm
;;; D. Thiebaut
;;; a simple demo program to test I/O with
;;; a C "wrapper" program
;;; 
;;; Assemble, link and run as follows:
;;;   nasm -f elf asm_io.asm        (do this only once)
;;;   nasm -f elf prog1.asm
;;;   gcc -o prog1 driver.c prog1.o asm_io.o
;;;   ./prog1
;;; 
%include "asm_io.inc"
        
%assign SYS_EXIT        1

        ;; -------------------------
        ;; data segment
        ;; -------------------------
        section .data
msg     db      "Hello! Please enter an integer number: ",0
msg2    db      "You have entered ",0
x       dd      0

        ;; -------------------------
        ;; code area
        ;; -------------------------
        section .text
        global  asm_main
asm_main:       

        mov     eax,msg               ; pass address of the string msg in eax
        call    print_string          ; call a function in asm_io library
                                      ; that will print the string msg

        call    read_int              ; call a function that reads an
        mov     [x], eax              ; integer from the keyboard and
                                      ; returns it in eax.  Save returned
                                      ; value in variable x

        mov     eax,msg2              ; print the string msg2
        call    print_string          ; ("you have entered")

        mov     eax,[x]               ; get integer user entered
        call    print_int             ; pass it via eax and call the
                                      ; function specialized in printing
                                      ; integer numbers

        call    print_nl              ; call the function that prints
                                      ; a new blank line

        ;; return to C program

        ret