Question

Write an assembly program (Data and Code) that uses loop to read 10 numbers and output the largest of those numbers, you can assume any length for those numbers.

80x86 assembly language

Answer 1

Codes

find out the largest among 8-bit n numbers, where size “10" is stored at memory address 2000 : 600 and the numbers are stored from memory address 2000 : 601 and store the result (largest number) into memory address 2000 : 800.

Example

Input data and memory address

10	20	21	22	23	24	25	36	26	27	28
600	601	602	603	604	605	606	607	608	607	608

Out put data

36

800

Algorithm –

1. Load data from offset 600 to register CL and set register CH to 00 (for count).
2. Load first number(value) from next offset (i.e 601) to register AL and decrease count by 1.
3. Now compare value of register AL from data(value) at next offset, if that data is greater than value of register AL then update value of register AL to that data else no change, and increase offset value for next comparison and decrease count by 1 and continue this till count (value of register CX) becomes 0.
4. Store the result (value of register AL ) to memory address 2000 : 800.

Program

MEMORY ADDRESS	MNEMONICS	COMMENT
500	MOV SI, 600	SI<-600
503	MOV CL, [SI]	CL<-[SI]
505	MOV CH, 00	CH<-00
507	INC SI	SI<-SI+1
508	MOV AL, [SI]	AL<-[SI]
50A	DEC CL	CL<-CL-1
50C	INC SI	SI<-SI+1
50D	CMP AL, [SI]	AL-[SI]
50F	JNC 513	JUMP TO 513 IF CY=0
511	MOV AL, [SI]	AL<-[SI]
513	INC SI	SI<-SI+1
514	LOOP 50D	CX<-CX-1 & JUMP TO 50D IF CX NOT 0
516	MOV [800], AL	AL->[800]
51A	HLT	END

Explanation –

1. MOV SI, 600 : set the value of SI to 600
2. MOV CL, [SI] : load data from offset SI to register CL
3. MOV CH, 00 : set value of register CH to 00
4. INC SI : increase value of SI by 1.
5. MOV AL, [SI] : load value from offset SI to register AL
6. DEC CL : decrease value of register CL by 1
7. INC SI : increase value of SI by 1
8. CMP AL, [SI] : compares value of register AL and [SI] (AL-[SI])
9. JNC 513 : jump to address 513 if carry not generated
10. MOV AL, [SI] : transfer data at offset SI to register AL
11. INC SI : increase value of SI by 1
12. LOOP 50C : decrease value of register CX by 1 and jump to address 50D if value of register CX is not zero
13. MOV [800], AL : store the value of register AL to offset 800
14. HLT : stop