The document outlines a NASM assembly program designed to check if a user's input string is a palindrome using stack operations. It includes various assembly commands and structures while encountering issues like segfaults and errors throughout the process. Several comments indicate areas for improvement and debugging within the code.

1. In NASM Assembly, problem is to determine if a user's dynamic input, formatted by a null-
terminated character, is or is not a palindrome. MUST use the stack (push & pop) to do so, with
only commands, mov, cmp, loop, and jump. I keep getting segfaults and early exits Current error is
Inferior 1 (process 3125) exited normally
---------------------------
global main ; exposes program entry point to the linker
extern printf ; declare external function
extern scanf ; declare external function
section .text ; start of code segment
main:
push rbp ; preserve base pointer
mov rbp,rsp ; copy stack pointer to base pointer
; Prompt for entry of a word to test if a palindrome
mov rdi,prompt ; prompt format string for printf
call printf ; call printf function from C library
; Input a word to input buffer (buf)
mov rdi,fmt_str ; format string for scanf
mov rsi,buf ; address of input buffer for scanf
call scanf ; call scanf function from C library
; TODO: Check null-terminated string at buf to see if a palindrome
L1:
; Is string a palindrome?
xor rax,rax ; clear index
mov rax,[buf-3] ; Address of last character
dec rsi ; index of last char
mov sil,1 ; assume input is palindrome
;Check for palidrome
cmp rdi,rsi ; compare indices
jge L3 ; exit loop if indices have crossed
mov dl, byte[buf+rdi] ; read from start of string
mov dh, byte[buf,rsi] ; read byte from end of string
cmp dl, dh ; compare bytes
jne L3 ; exit loop if bytes differ (NOT palindrome)
inc rdi ; advance index from start
dec rsi ; advance index from end
jmp L1 ; check_palindrome, repeat loop
L3: ;not_palindrome:
mov al,0 ; indicate input is NOT a palindrome
mov sil,byte[str_is_not_palindrome] ; save to memory
L2: ;Is a palindrome
mov al,1 ; indicate input is a palindrome
mov sil,byte[str_is_not_palindrome] ; save to memory

2. ; TODO: Move either str_is_palindrome or str_is_not_palindrome
; to RDI to output appropriate message
; Output message, address of output string expected in RDI
call printf ; call printf function from C library
pop rbp ; restore base pointer
mov rax, 0 ; exit status (0 = success)
ret
section .data ; start of initialized data segment
prompt db "Enter a word: ",0 ; Prompt for entry
buf_confirm db "You entered %s.",0xa,0
str_is_palindrome db "This word is a palindrome.",0xa,0
str_is_not_palindrome db "This word is not a palindrome.",0xa,0
fmt_str db "%s",0 ; Input format string for scanf
section .bss ; start of uninitialized data segment
buf resb 100 ; input buffer, for entry of a word