Draw a detailed flowchart and write an ARM assembly program to determine whether

Question

Draw a detailed flowchart and write an ARM assembly program to determine whether a string of printable ASCII letters (from a to z or from A to Z, case insensitive) stored in memory is a palindrome (i.e., the letters in the string are the same from left to right as from right to left, case insensitive) or not. If palindrome, you should store 1 in r0. if not, you store 2 in r0 Your code should be highly optimized. Use as few instructions as possible (as little as 21 assembly instructions only)!! gnore all characters that are not letters. You should also treat capital and small letters the same, i.e., case insensitive. For example, "madam", "deleveled", "Noon", "He lived as a devil, eh?", and "Was it a car or a cat I saw?" are palindrome strings. However, "madam, I am Adam." is not a palindrome string. A string can have even or odd number of characters and must end with character 0x00 (i.e., the ASCII code of the null character) Define in your assembly program the string as follow: STRING DCB "He lived as a devil, eh?" string EoS end of string DCB 0x00

Explanation / Answer

Program : ( with explanation)

mov bl,50 ; Starting Address of the memory

mov dl,0 ; number of characters make up the string

loop:

in 00 ;read the input from keyboard

cmp al, 2E ;checking to see if input is a fullstop

jz palindrome ;loop to see if input is a palindrome

mov [bl], al ;save input in the memory address

inc bl ;goto the next memory addr in bl

inc dl ;increment dl by 1 to length of the string

push al

jmp loop

palindrome:

cmp dl,0 ;check if it has goes through whole string

jz is_palin ;loop it has then string is a palindrome

mov bl, 50 ;bring back first input character

mov dl,[bl]

pop cl ;put last input character

cmp cl,dl ;check if the two values are the same

jnz not_palindrome ;if they are not same,then loop to not_palindrome

inc bl ;go to next input address

dec dl ;take away 1 from length of the string

jmp palindrome ;loop back to the start of the palindrome

not_palindrome:

mov dl,c0

mov cl,6E

mov [dl],cl ;print the character "n" to the vdu

jmp done ; do not execute code at is_palin

is_palin:

mov dl,c0

mov cl,79

mov [dl],cl ;print the character 'y' to the vdu

end

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