.model smal1 .stack 100h .code main proc mov ah, 1 int 21h ; enter key routine m

Question

.model smal1 .stack 100h .code main proc mov ah, 1 int 21h ; enter key routine mov cl, alsaving the key pressed from AL into CL mov ch, al mov bl, 8 my counter binloop: shl cl, 1 jc displ mov dl, 30h call disp dec bl i dec the counter by 1 jnz binloop call hex 4c00h terminate the program and return to mov ax, int 21h displ: MSDOs mov dl, 31h call disp dec bl i dec the counter by 1 jnz binloop call hex 4c00h mov ax, int 21h terminate the program and return to MSDOs hex proc mov cl, ch call shrcl mov dl, cl add dl, 30h call disp mov cl, ch call shlcl call shrcl mov dl, cl add dl, 30h call disp ret

Explanation / Answer

.model small //every module have segment(like code,data,stack) must begin with .model directive

.stack 100h //starting stcak segment of 100h size

.code //starting code segment where our actual program lies

main proc //this starting main of name proc

mov ah,1; //we are moving 1 to ah register

int 21h; //it is software interrupt that invokes DOS API functions

mov cl,al; //moving the data at al register to cl register

mov ch,al; //moving the data at al register to ch register

mov bl,8; //moving constant value 8 to register bl

binloop: //this is a label named binloop,at miidle of code ,if we want to,we can come back to this part and can run code

shl cl,1; //left shifts value at cl by 1 byte

jc displ //jc-(jump on carry).if we get carry while shifting value in cl ,we goes to displ

mov dl,30h; //move 30h into dl register

call disp; //it called unconditional sub-routine.Without any condition, we automatically goes to disp label

dec bl; //decrement bl register value by 1

jnz binloop; //jnz-(jump on non zero).If bl value is not equal to zero,we jumps to binloop label

call hex; //directly jumps to hex sub-routine

mov ax,4c00h; //moving 4c00h value to ax register

int 21h; //terminate program.

displ: //this is label named displ

mov dl,31h; //move 31h value into dl register

call disp; //jumps to disp sub-routine

dec bl; // decrement value at bl register by one

jnz binloop //if bl is nt equal to zero,jumps to binloop

call hex //calls sub-routine hex

mov ax,4c00h //mov 4c00h value to ax register

int 21h; //terminates program

hex proc //this subroutine named hex

mov cl,ch ..moving value at h register to cl register

call shrcl //calls sub-routine shrl

mov dl,cl //moves value at cl register to dl register

add dl,30h //adds 30h to value at dl regsiter and stores in dl regsiter

call disp //calls sub-routine disp

mov cl,ch //moves value at ch register to cl register

call shlcl //calls sub-routine shlcl

call shrcl //calls sub-routine shrcl

mov dl,cl //moves value at cl register to dl register

add dl,30h //adds value 30h to value at dl and stores in dl

call disp // calls sub-routine disp

ret //returns to original execution from where you come to this sub-routine

hex proc //thsi is sub-routine proc

mov cl,ch //moves value at cl register to ch register

call shrcl //calls sub-routine shrcl

mov dl,cl //moves value at cl regsiter to dl register

add d1,30h //adds value 30h to value at dl register and stores in dl register

call disp //calls sub-routine disp

ret //returns to original execution from where we come to this sub-routine

hex endp //endp-(end of procedure).thsi is end of procedure hex

shrcl proc //this sub-routine shrcl

shr c1,1 //shifts right cl register by one byte

shr c1,1 //shifts right cl register by one byte

shr c1,1 //shifts right cl register by one byte

shr c1,1 //shifts right cl register by one byte

ret //returns to original execution from we come to this sub-routine

shlcl endp //this is end of procedure of shlcl

disp proc //this is sub-routine disp

cmp dl,39h //moves 39h value to dl register

js skip //js-(jump if sign flag is set),if sign sets because of above instruction,goes to skip label

add dl,7 //adds value 7 to value at register dl and stores in dl regsiter

skip: //this label named skip

mov ah,6 //moves value 6 to ah register

int 21h //terminates the procedure

ret //returns to original execution from where we come to this sub-routine

disp endp //this end of procedure of disp

main endp //end of procedure of main

end main //ends main

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