Exercises

Q$1)$ Write an assembler code to reverse string $x$ in order; use LODSB and STOSB strings; where $x$ DB $$ HELLO WORLD'

x DB 'HELLO WORLD'

y DB $11$ Duo$(?)$

Q$2)$ Write an assembler codes to scan string $x$ for $*$ character ; replacing it by space.

$x$ DB $\text{'}AB{C}^{**}+GFD{K}^{****}KLM\text{'}$

Q$3)$ write an assembler codes to find factorial of values in $x$ memory locations; storing the result into Y memory locations; call a procedure to find factorial of numbers in $x$; where :

Q$4)$ Write a sequence of instructions using $($LODSB and STOSB$)$ that copy each alphabet from X string to Y string, converting it to lowercase $.$ Note: setting bit $5$ in an uppercase character will convert it to lowercase

X DB 'ABCDEFGHI'

Y DB LENGTHOF X DUP$(0)$

The value of $Y$ after executing the following code is:

X DB $4$

Y DB

MOV CX$,2$

L: CALL SUM

LOOP L

MOV Y$,$ AL

HLT

SUM PROC

MOV AH$,$ X

ADD AL$,$ AH

RET

SUM ENDP

$Y=$

What is the value of $Cx$ after execution the following codes?

STR DB "ABCDE"

MOV DI$,$ OFFSET STR

MOV CX$,5$

MOV AL$,\text{'}$C

REPNE SCASB

$Cx=$

What is the value of $AL$ after execution the following codes?

X DB "ABCDE"

Y DB "ABHDE"

MOV SI$,$OFFSET Y

MOV DI$,$OFFSET X

MOV CX$,5$

REPE CMPSB

LODSB

$AL=$

$4.$ The values of array $Y$ after executing the following code is:

$XDB$ 'ASSEMBLY'

$YDB5$ DUP$(\text{'}*\text{'})$

$STD$

MOV $SI,$ OFFSET $X+3$

MOV $DI,$ OFFSET $Y+4$

MOV $CX,3$

REP MOVSB

MOV $AX,\text{'}\frac{?}{\text{\#}}\text{'}$

STOSB

$Y=$

The value of $Ax$ after executing the following code is:

ARRAY $DB8,3,2,4$

$STC$

MOV $AL,0$

MOV $CX,4$

MOV $SI,$ OFFSET ARRAY

$L$: ADC $AL,[SI]$

ADD $SI,1$

LOOP $L$

$AX=$