quotes.asm

; assembly code for print a list of quotes of variable length strings
;This code uses an array of quotes and array of quote lengths

section	.data
;Welcome to list of quotes message
;Welcome message size
welcome db "Welcome to List of quotes", 10
welcomeLen equ $-welcome

;Same as endl in C++
cr db 10

; The quotes and quote lengths for the arrays 
Quote1 db "If life were predictable it would cease to be life, and be without flavor."
Quote1len equ $-Quote1
Quote2 db "Life is what happens when you're busy making other plans. "
Quote2len equ $-Quote2
Quote3 db "Always remember that you are absolutely unique. Just like everyone else. "
Quote3len equ $-Quote3
Quote4 db "The future belongs to those who believe in the beauty of their dreams. "
Quote4len equ $-Quote4
Quote5 db "You will face many defeats in life, but never let yourself be defeated. "
Quote5len equ $-Quote5

;the array we use to point to the quotes
listQuotes:    
  dq  Quote1 ; the pointer to the quotes are stored in 8 bytes
  dq  Quote2
  dq  Quote3
  dq  Quote4
  dq  Quote5
  
;the array we use to point to the quote lengths
listQLen:    
  dq  Quote1len ; the pointer to the quote lengths are stored in 8 bytes
  dq  Quote2len
  dq  Quote3len
  dq Quote4len
  dq Quote5len
  
  
segment .bss

section	.text
   global _start   ;must be declared for linker (ld)
_start:	
call displayWelcome ; call function for welcome message
call newLine ; call function for newline
mov  rax,5      ;number of quotes to loop through
mov r8, listQuotes ; point to first quote
Mov r9, listQLen ; point to the length of first quote

; main function to display the quotes
top:  
  push rax ; push rax on stack (The number of quote we are dealing with)
  call displayQuote ; function to display quote
  call newLine ; function to create a newline
  pop rax ; get where we are in the list of quotes back from the stack
  add r8,8 ; add on 8 bytes as using dq data type
  add r9,8 ; add on 8 bytes as using dq data type
  dec  rax        ;decrement counter so going down list of quotes
  jnz  top        ;if counter not 0, then loop again as not at end of list of quotes
  call done ; end program

; Function to create a New line like endl in C++
 newLine:
  mov eax,4 	; Put 4 in eax register into which is system 
              ;call for write (sys_write)	
  mov ebx,1 	; Put 1 in ebx register which is the standard 
			        ; output to the screen 
	mov ecx, cr	; Put the newline value into ecx register
	mov edx, 1	; Put the length of the newline value into edx 
			        ; register
	int 80h 	; Call the kernel with interrupt to check the 
			      ; registers and perform the action of moving to 
			      ; the next line like endl in c++
	ret	; return to previous position in code 

;Function to display welcome to game message
displayWelcome:
   mov  edx,welcomeLen      ;message length
   mov  ecx, welcome   ;message to write
   mov  ebx, 1     ;file descriptor (stdout)
   mov  eax, 4     ;system call number (sys_write)
   int  0x80       ;call kernel
   ret

;Function to display quotes
displayQuote:
   mov  edx, [r9] ;message length content of register r9
   mov  ecx, [r8];message to write content of register r8
   mov  ebx, 1     ;file descriptor (stdout)
   mov  eax, 4     ;system call number (sys_write)
   int  0x80       ;call kernel
   ret

; Function to end the program
 done:
   mov  eax, 1     ;system call number (sys_exit)
   int  0x80       ;call kernel