Question

X86 Assembly MASM

Questions below

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;; Answer each question below by writing code at the APPROPRIATE places at the end
;;;;; of the file as indicated.

;;;;; Q2: Write the directive to bring in the IO library          

;;;;; Q3: Create a constant called DAYS_PER_WEEK and initialize it to 5
;;;;;     Create a constant called WEEKS_PER_YEAR and initialize it to 49

;;;;; Q4: Create a constant called DAYS_PER_YEAR by using DAYS_PER_WEEK and
;;;;;     WEEKS_PER_YEAR (of Q3) in an integer expression constant

;;;;; Q5: Define an array of 10 signed doublewords, use any array name you like.
;;;;;     Initialize:
;;;;;   - the 1st element to the DAYS_PER_YEAR value defined in Q4
;;;;;   - the 2nd element to the hexadecimal value: B285
;;;;;   - the 3rd element to the 4-bit binary value: 1001
;;;;;   - the 4th element to the decimal value: -250
;;;;; and leave the rest of the array uninitialized.

;;;;; Q6. Define the string "Output = ", use any variable name you like.

;;;;; Q7. Define a prompt that asks the user for a negative number

;;;;; Q8. Write code to prompt the user for a number, using the prompt string that
;;;;;     you defined in Q7

;;;;; Q9. Write code to read in the user input, which is guaranteed to be negative

;;;;; Q10. Write code to print "Output = " and then print to screen the user input
;;;;;       which should be a negative value

;;;;; Q12. Write code to print "Output = " and then print the first element of the
;;;;;      array defined in Q5, without the + symbol in front.

;;;;; Q13. Build, run, and debug your code
;;;;; Your output should be similar to this (without the commented explanation)

;;;;; Enter a negative number: -10
;;;;; Output = -10                          
;;;;; Output = 245                          
;;;;; Press any key to continue . . .

;;;;; Q14. At the end of the source file, without using semicolons (;), add a comment
;;;;;      block to show:
;;;;;       - how bigData appears in memory. You should copy from the debugger memory
;;;;;        window and it should be the same 8 bytes as in lab 2)
;;;;;      - note that the 8 bytes in memory doesn't look identical to the 8 bytes
;;;;;        that are used to define bigData. Explain why the 8-byte sequence
;;;;;        are different

;;;;; 1pt EC (Extra Credit):
;;;;; In the same comment block, explain how many bytes the array of Q5 occupy
;;;;; in memory.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;   Put your answers below this line

.data
bigData QWORD 9876543210fedcbah       ; same bigData value as lab 2

.code
main PROC

   exit  
main ENDP

END main

Answer 1

part 1
section .text
   global _start          ;must be declared for linker (gcc)
        
_start:                   ;tell linker entry point
   mov  edx,1             ;message length
   mov  ecx,choice        ;message to write
   mov  ebx,1             ;file descriptor (stdout)
   mov  eax,4             ;system call number (sys_write)
   int  0x80              ;call kernel

   mov  eax,1             ;system call number (sys_exit)
   int  0x80              ;call kernel

section .data     ;variable declaration start here

part 2

DAYS_PER_WEEK DB 5 ;DB=Define Byte allocates 1 byte

WEEKS_PER_YEAR DB 9

part3

MOV AL ,DAYS_PER_WEEK ;load variable to AL

MOV BL,WEEKS_PER_YEAR ;;load variable to BL

MUL BL                        ;multiplication

MOV DAYS_PER_YEAR ,AL ;move result to days_per_year

part 4

;for 1001 hex is 9 and for -250 decimat to hex is -FA

array1   DW  DAYS_PER_YEAR , B285 , 9 , -FA , 0 , 0 , 0 , 0,0,0