CS401 assignment no 3 Complete Solution

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  Solution CS411 Assignment 3 CS402 Assignment Solution CS304 Assignment no 3 Solution CS403 assignment no 3 Complete Solution Assignment No 3 cs301 solution CS401 assignment no 3 Complete Solution

Code

[org 0x0100]

jmp start

oldisr: dd 0 ; space for saving old isr

; keyboard interrupt service routine

kbisr:

push ax

push es

mov ax, 0xb800

mov es, ax ; point es to video memory

in al, 0x60 ; read a character from keyboard port

cmp al, 0x11 ; has the 'w' key pressed

jne nomatch ; no, go to nomatch

mov byte [es:0], '1' ; yes, print 1

mov byte [es:2], '5' ; yes print 0

jmp exit ; leave interrupt routine

nomatch:

pop es

pop ax

jmp far [cs:oldisr] ; call the original ISR

exit

mov al, 0x20

out 0x20, al ; sent EOI to PIC

pop es

pop ax

iret ; return from interrupt

start:

xor ax, ax

mov es, ax ; point es to IVT base

mov ax, [es:9*4]

mov [oldisr], ax ; save offset of old routine

mov ax, [es:9*4+2]

mov [oldisr+2], ax ; save segment of old routine

cli ; disable interrupts

mov word [es:9*4], kbisr ; store offset at n*4

mov [es:9*4+2], cs ; store segment at n*4+2

sti ; enable interrupt

mov dx, start ; end of resident portion

add dx, 15 ; round up to next para

mov cl, 4

shr dx, cl ; number of paras

mov ax, 0x3100 ; terminate and stay residant

int 0x21

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