230 lines
9.4 KiB
NASM
230 lines
9.4 KiB
NASM
; THIS CODE HAS NOT BEEN TESTED AND IS NOT FULLY OPERATIONAL.
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; Problem Statement: Write X86/64 ALP to perform multiplication of two 8-bit hexadecimal numbers. Using successive addition and add-and-shift methods. (Use of 64-bit registers is expected).
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; Code from Microprocessor (SPPU - Second Year - Computer Engineering - Content) repository on KSKA Git: https://git.kska.io/sppu-se-comp-content/Microprocessor/
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;------------------------------
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%macro print 2
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mov rax,1
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mov rdi,1
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mov rsi,%1
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mov rdx,%2
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syscall
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%endmacro
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%macro accept 2
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mov rax,0
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mov rdi,0
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mov rsi,%1
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mov rdx,%2
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syscall
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%endmacro
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%macro dispmsg 2 ;macro for display
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mov rax,1 ;standard ouput
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mov rdi,1 ;system for write
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mov rsi,%1 ;display message address
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mov rdx,%2 ;display message length
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syscall ;interrupt for 64-bit
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%endmacro
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%macro exitprog 0 ;macro for exit
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mov rax,60 ;system for exit
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mov rdx,0
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syscall ;interrupt for 64-bit
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%endmacro
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%macro gtch 1 ;macro for accept
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mov rax,0 ;standard input
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mov rdi,0 ;system for read
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mov rsi,%1 ;input the message
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mov rdx,1 ;message length
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syscall ;interrupt for 64-bit
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%endmacro
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section .data
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nwline db 10
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m0 db 10,10,"Program to multiply two numbers using successive addition and add-and-shift method"
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l0 equ $-m0
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m1 db 10,"1. Successive Addition Method",10,"2. Add-and-Shift Method",10,"3. Exit",10,10, "Choose an option (1/2/3 <ENTER>): "
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l1 equ $-m1
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m2 db 10,"Enter the multiplicand (2 digit HEX no): "
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l2 equ $-m2
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m3 db 10,"Enter the multiplier (2 digit HEX no): "
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l3 equ $-m3
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m4 db 10,"Multiplication using Successive Addition Method: "
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l4 equ $-m4
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m5 db 10,"Multiplication using Add-and-Shift Method: "
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l5 equ $-m5
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section .bss
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mcand resq 1 ;reserve 1 quad for multiplicand
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mplier resq 1 ;reserve 1 quad for multiplier
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input resb 1 ;reserve 1 byte for input
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output resb 1 ;reserve 1 byte for output
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choice resb 1 ;reserve 1 byte for choice
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section .text
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global _start ;starting of main program
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_start :
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dispmsg m0,l0 ;displaying the menu
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back:
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dispmsg m1,l1 ;displaying the first message
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gtch input ;to read and discard ENTER key pressed.
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mov al, byte[input] ;get choice
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mov byte[choice],al
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gtch input ;to read and discard ENTER key pressed.
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mov al, byte[choice]
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cmp al, '1' ;compare contents of al with 1
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je succ_add ;if equal the jump to succ_add procedure
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cmp al, '2' ;compare the contents of al with 2
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je add_shift ;if equal then jump to add_shift procedure
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cmp al, '3' ;compare the contents of al with 3
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jnz back ;if not zero then jump to back
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exitprog ;exit program
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;-------- SUCCESSIVE ADDITION METHOD ---------
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succ_add: ;successive addition procedure
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dispmsg m2,l2 ;Displaying the second message
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call getnum ;call getnum procedure
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mov [mcand],rax ;mov contents of rax(multiplicand) into mcand buffer
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gtch input ;to read and discard ENTER key pressed
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dispmsg m3,l3 ;Displaying the third message
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call getnum ;call getnum procedure
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mov [mplier],rax ;mov contents of rax(multiplier) into mplier buffer
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gtch input ;to read and discard ENTER key pressed
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mov rax,0 ;clearing the rax register
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dispmsg m4,l4 ;displaying the fourth message
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call succ_addition ;call the successive addition method
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jmp back ;jump to back
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;-------- ADD AND SHIFT METHOD ---------
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add_shift: ;add and shift procedure
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dispmsg m2,l2 ;Displaying the second message
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call getnum ;call getnum procedure
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mov [mcand],rax ;mov contents of rax(multiplicand) into mcand buffer
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gtch input ;to read and discard ENTER key pressed
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dispmsg m3,l3 ;Displaying the third message
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call getnum ;call getnum procedure
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mov [mplier],rax ;mov contents of rax(multiplier) into mplier buffer
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gtch input ;to read and discard ENTER key pressed
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mov rax,0 ;clearing the rax register
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dispmsg m5,l5 ;displaying the fifth message
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call add_and_shift ;call the add-and-shift method
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jmp back ;jump to back
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getnum: ;procedure to get a 2 digit hex no from user
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; number returned in rax
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mov cx,0204h ;02 digits to display and 04 count to rotate
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mov rbx,0 ;clearing rbx register
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ll2: ;loop 2
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push rcx ;syscall destroys rcx.Rest all regs are preserved
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gtch input ;to read and discard ENTER key pressed
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pop rcx ;pop the contents of rcx
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mov rax,0 ;clearing the contents of rax
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mov al,byte[input] ;get choice
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sub rax,30h ;subtract 30h from contents of rax
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cmp rax,09h ;compare the contents of rax register with 09h
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jbe skip1 ;if equal then jump below to skip1 label
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sub rax,7 ;subtract 7 from contents of rax register
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skip1: ;skip1 label
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shl rbx,cl ;shift multiplicand and count to the left
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add rbx,rax ;add contents of rax register to the contents of rbx register
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dec ch ;decrement the contents of ch register
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jnz ll2 ;if not zero then jump to loop 2
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mov rax,rbx ;mov contents of rbx register into rax register
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ret ;return
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succ_addition: ;procedure for successive addition
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mov rax,0 ;clearing rax register
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mov rcx,8 ;taking count of 8 in rcx register
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mov dl,[mplier] ;multiplier is 8 bits so it occupies dl
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mov bl,[mcand] ;multiplicand is 8 bits so it occupies bl
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;we will put Q in higher 8 bits of ax (i.e. ah)
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;and multiplier in lower 8 bits of ax (i.e. al)
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mov ah,0 ;clearing ah register
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mov al,dl ;ah already 0 and al now contains multiplier
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ll3: ;loop 3 (s3)
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mov dh,al ;mov contents of al into dh as dh is used as temporary
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and dh,1 ;check d0 bit of multiplier
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jz ll8 ;if d0 bit was zero, Z flag will be set (s2)(if zero jmp to loop 8)
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add ah, bl ;d0 bit of multiplier is set
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;so add multiplicand to Q(add bl into ah)
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ll8: ;loop 8 (s2)
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shr ax,1 ;shift both Q (ah) and multiplier (al) right 1 bit
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dec rcx ;decrement contents of rcx
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jnz ll3 ;if not zero then jump to loop 3 (s3)
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call dispnum ;call procedure dispnum
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ret ;return
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add_and_shift: ;procedure for add-and-shift method
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mov rax,0 ;clearing rax register
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mov rcx,8 ;taking count of 8 in rcx register
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mov dl,[mplier] ;multiplier is 8 bits so it occupies dl
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mov bl,[mcand] ;multiplicand is 8 bits so it occupies bl
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;we will put Q in higher 8 bits of ax (i.e. ah)
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;and multiplier in lower 8 bits of ax (i.e. al)
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mov ah,0 ;clearing ah register
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mov al,dl ;ah already 0 and al now contains multiplier
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ll3_shift: ;loop 3 (s3) for add-and-shift
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mov dh,al ;mov contents of al into dh as dh is used as temporary
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and dh,1 ;check d0 bit of multiplier
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jz ll8_shift ;if d0 bit was zero, Z flag will be set (s2)(if zero jmp to loop 8)
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add ah, bl ;d0 bit of multiplier is set
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;so add multiplicand to Q(add bl into ah)
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ll8_shift: ;loop 8 (s2) for add-and-shift
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shl ax,1 ;shift both Q (ah) and multiplier (al) left 1 bit
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dec rcx ;decrement contents of rcx
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jnz ll3_shift ;if not zero then jump to loop 3 (s3) for add-and-shift
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call dispnum ;call procedure dispnum
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ret ;return
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dispnum: ;procedure to display the result
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mov rbx,rax ;move contents of rax register into rbx register
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mov rcx,1004h ;16 digits to display and 04 count to rotate
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ll6: ;loop 6
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rol rbx,cl ;rotate multiplicand and count to the left
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mov rdx,rbx ;mov contents of rbx register into rdx register
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and rdx,0fh ;anding contents of rdx register with 0fh
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add rdx,30h ;adding contents of rdx register with 30h
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cmp rdx,039h ;comparing the contents of rdx register with 39h
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jbe skip4 ;if equal then jump below to skip4 label
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add rdx,7 ;add 7 to the contents of rdx register
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skip4: ;skip4 label
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mov byte[output],dl ;mov contents of dl register into output buffer in bytes
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push rcx ;push the contents of rcx register
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dispmsg output,1 ;displaying the output
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pop rcx ;pop the contents of rcx
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dec ch ;decrement the count(contents of ch)
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jnz ll6 ;if not zero the jump to loop 6
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ret ;return
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