Writing Loops $($FOR and WHILE loops$)$

Writing Decision statements $($IF statements$)$

Writing Functions

Things you will need

Virtualbox virtual machine $($with all the tools$)$

A text editor $($provide by the VM $-$ VS code, Gedit, VIM, $...)$

The Nasm assembler $($provided by the VM$)$

The ld linker $($provided by the VM$)$

Description

For this assignment, you are going to write an assembler program that will test if sentences are palindromes.$$ The high$-$level pseudocode is as follows:

loop until the user is finished

$$ prompt the user for a string

$$ read a string from the keyboard

$$ test the string to determine if it is a palindrome

$$ if so$,$ then

$$ print $"$It is a palindrome"

$$ else

$$ print $"$It is NOT a palindrome"

end loop $$

Your program will use the SYS$\_$READ Linux call to read a sentence from the keyboard. The user will signify that they are finished by pressing without entering a sentence.$$ After a call to SYS$\_$READ in which the user presses without entering a string, the SYS$\_$READ places a newline at the beginning of the buffer $($a newline byte contains the value $10).$ So$,$ you should test after the call to SYS$\_$READ, and if the first byte in the buffer is a newline, then your program should exit nicely $($by calling SYS$\_$EXIT$).$

Also, you will implement a function called is$\_$palindrome in assembler that your program will call to determine if a buffer contains a palindrome.$$ The prototype for is$\_$palindrome is as follows:

int is$\_$palindrome$($char $*$buffer$,$ int len$)$;

The function returns a $1$ if the buffer contains a palindrome, or a $0$ if the buffer does not contain a palindrome.$$ Note that the len that is passed should be the length of the string not counting the newline at the end that SYS$\_$READ includes.$$ Also, remember that SYS$\_$READ returns the number of bytes read in EAX $($however$,$ do not forget to decrement EAX by $1$ so that you to not include the newline in the length$).$ To get credit for this assignment, you must follow all C calling conventions for a $32$ bit program on the Intel architecture $($what we have been studying in class$)$ for the is$\_$palindrome function.$$

The program is to be written and tested on the virtual machine given in class, must compile using the nasm assembler, and must link using the ld linker.$$ To compile the program, you will enter the following commands:

nasm $-$g $-$f elf $-$F dwarf $-$o palindrome.o palindrome.asm

ld palindrome.o $-$m elf$\_$i$386-$o palindrome

Do not use any macros or libraries for this assignment.

The following is a version of this program written in C that you can use as a reference.$$ Your program should behave similarly to it$.$

#include #include int is$\_$palindrome$($char $*$ buf, int len$)$; int main$()\{$ char buf$[1024]$; int count; write$(1,$ "Please enter a string:

$",23)$; count $=$ read$(0,$ buf, $1024)$; while $($buf$[0]!=\text{'}$

$\text{'})\{$ count$--$; if $($is$\_$palindrome$($buf$,$ count$))\{$ write$(1,"$It is a palindrome

$",20)$; $\}$ else $\{$ write$(1,"$It is NOT a palindrome

$",23)$; $\}$ write$(1,$ "Please enter a string:

$",23)$; count $=$ read$(0,$ buf, $1024)$; $\}$ return $0$; $\}$ int is$\_$palindrome$($char $*$buf$,$ int len$)\{$ int i$,$ j; for $($i $=0,$ j $=$ len $-1$; i $<$ len$/2$; i$++,$ j$--)$ if $($buf$[$i$]!=$ buf$[$j$])$ return $0$; return $1$; $\}$

The following shows an example run of this program:

$ $./$pal$\_$in$\_$c

Please enter a string:

$1221$

It is a palindrome

Please enter a string:

rats live on no evil star

It is a palindrome

Please enter a string:

$1$

It is a palindrome

Please enter a string:

beef

It is NOT a palindrome

Please enter a string:

$1122322211$

It is NOT a palindrome

Please enter a string:

$

The following command will compile the above example program written in C:

gcc $-$g $-$Wall $-$o pal$\_$in$\_$c pal$\_$in$\_$c$.$c

$($Note: if you have gcc produce assembler from the C code and submit the gcc generated assembler, then the professor will know and give you a grade of $0).$ write the program