section .data
	; Define strings and their lengths
	introMsg dw "ALP to detect the operating mode of the microprocessor and display the contents of some system registers"
	introMsgLen equ $ - introMsg
    
	gdtrMsg db 10,10,"Contents of GDTR : ",10
	gdtrMsgLen equ $ - gdtrMsg
    
	ldtrMsg db 10,10,"Contents of LDTR : ",10
	ldtrMsgLen equ $ - ldtrMsg
    
	idtrMsg db 10,10,"Contents of IDTR : ",10
	idtrMsgLen equ $ - idtrMsg
    
	trMsg db 10,10,"Contents of TR : ",10
	trMsgLen equ $ - trMsg
    
	mswMsg db 10,10,"Contents of MSW (CR0) register : ",10
	mswMsgLen equ $ - mswMsg
    
	protectedMsg db 10,10,"The Microprocessor is in the protected mode"
	protectedMsgLen equ $ - protectedMsg
    
	proMsg db 10,10,"The contents of the system registers are as follows : "
	proMsgLen equ $ - proMsg
    
	realMsg db 10,10,"The Microprocessor is in the real mode"
	realMsgLen equ $ - realMsg
    
	colon db "  :  "
	colonLen equ $ - colon
    
section .bss
	; Define uninitialized memory to store system register values
	gdtr resd 1 ;to store 48-bit GDTR value-resd(32-bit) and resw(16-bit).
     	resw 1
    	 
	ldtr resw 1 ;to store 16-bit LDTR
    
	idtr resd 1  ;to store 48-bit IDTR value-resd(32-bit) and resw(16-bit).

     	resw 1
    	 
	tr resw 1
    
	msw resd 1
    
	result resb 4
    
%macro write 2
	; Define a macro for writing to stdout using syscall
	mov rax,1        	; syscall number for sys_write
	mov rdi,1        	; file descriptor 1 (stdout)
	mov rsi,%1       	; pointer to the message to be printed
	mov rdx,%2       	; length of the message
	syscall
%endmacro

section .text
	global _start

_start:
     	; Print introductory message
     	write introMsg,introMsgLen
   	 
     	smsw eax         	; Store the contents of the MSW register into the EAX register.
     	bt eax,0         	; Copy the 0th least significant bit from EAX to the carry flag.
    	 
     	jc protected_mode	; If CF is set, processor is in protected mode
    	 
     	write realMsg,realMsgLen  ; Print message indicating real mode
    	 
     	jmp endOfProgram	; Jump to end of program
    	 
protected_mode :
     	write protectedMsg , protectedMsgLen  ; Print message indicating protected mode
    	 
     	write proMsg , proMsgLen           	; Print message indicating contents of system registers
    	 
     	sgdt [gdtr]     	; Store the content of the global descriptor table register (GDTR) in gdtr
     	sldt [ldtr]     	; Store LDTR
     	str [tr]        	; Store TR
     	smsw [msw]      	; Store MSW
    	 
     	; Print contents of GDTR
     	write gdtrMsg,gdtrMsgLen
     	mov bx,[gdtr+4]  ; Move upper half of GDTR into bx reg.
     	call disp
     	mov bx,[gdtr+2]
     	call disp
     	write colon , colonLen
     	mov bx,[gdtr]
     	call disp
    	 
     	; Print contents of LDTR
     	write ldtrMsg,ldtrMsgLen
     	mov bx,[ldtr]
     	call disp
    	 
     	; Print contents of IDTR
     	write idtrMsg,idtrMsgLen
     	mov bx,[idtr+4]
     	call disp
     	mov bx,[idtr+2]
     	call disp
     	write colon , colonLen
     	mov bx,[idtr]
     	call disp
    	 
     	; Print contents of TR
     	write trMsg,trMsgLen
     	mov bx,[tr]
     	call disp
    	 
     	; Print contents of MSW
     	write mswMsg,mswMsgLen
     	mov bx,[msw+2]   ; Upper half of CR0 or MSW
     	call disp
     	mov bx,[msw]
     	call disp
    	 
endOfProgram:    
	; Terminate the program
	mov rax, 60
	mov rdi, 0
	syscall
    
disp:
    	; Procedure to convert binary to ASCII and print
    	mov rdi, result  	; Point rdi to result variable
    	mov cx,04        	; Load count of rotation in cl
up1:
    	rol bl,04        	; Rotate number left by four bits
    	mov dl,bl        	; Move lower byte in dl
    	and dl,0fh       	; Get only LSB
    	cmp dl,09h       	; Compare with 39h
    	jg add_37        	; If greater than 39h skip add 37
    	add dl,30h       	; Else add 30
    	jmp skip1        	; Skip to add_37
add_37:
    	add dl,37h       	; Add 37
skip1:  
    	mov [rdi],dl     	; Store ASCII code in result variable
    	inc rdi          	; Point to next byte
    	dec cx           	; Decrement the count of digits to display
    	jnz up1          	; If not zero, repeat
   	 
    	write result , 4 	; Write the result to stdout
   	 
    	ret               	; Return