Q3: Convert capital Character to small Character (lowercase)

Assembly

org 100h

.data

dt1 dB 'COMPUTER'

dt2 db 8 dup(0)

.code

mov ax,@data

mov ds,ax

mov si,offset dt1

mov di,offset dt2

MOV BL,20H

MOV CX,08

label:

MOV AL,[si]

ADD AL,BL

MOV [DI],Al

INC SI

INC DI

LOOP label

hlt

another way :-
-to convert small Character to capital Character only when find

org 100h

.DATA
DT1 DB 'University Of Technology'
DT2 DB 24 DUP(0)
.CODE
MOV AX,@DATA
MOV DS,AX
MOV SI,OFFSET DT1
MOV DI,OFFSET DT2
MOV BX,0000H
MOV CX,18H

A:MOV AL,[SI+BX]
CMP AL,'a'
JGE L
JMP X

L:CMP AL,'z'
JLE L1
JMP X

L1:SUB AL,20H

X:MOV [DI+BX],AL
INC BX
LOOP A

HLT