Write a simple 8086 assembly program that:
- Load AL by an arbitrary number,
- Check whether it is an odd/even number,
- If it is an odd number, it will be converted to its next larger even number and will be shown in port 0 in the trainer kit.
- If it is an even number, it will be converted to its previous smaller odd number and will be shown in port 0 in the trainer kit.
Assuming that the trainer kit has a display unit connected to port 0 and the user will input the arbitrary number through port 1, the following code can be used:
MOV AH, 01 ; load input from port 1
INT 21H ; read character from port 1
SUB AL, 30H ; convert ASCII to binary
AND AL, 01H ; check if LSb is set (odd number)
JZ EVEN ; jump to even number conversion if LSb is not set
ADD AL, 1 ; add 1 to convert odd number to even number
JMP DISPLAY ; jump to display result
EVEN:
SUB AL, 1 ; subtract 1 to convert even number to odd number
DISPLAY:
ADD AL, 30H ; convert binary to ASCII
MOV AH, 02 ; prepare for output to port 0
MOV DL, AL ; copy result to output register
MOV DX, 0080H ; select port 0 for output
INT 21H ; write result to port 0
The program works as follows:
1. Load input from port 1 and convert it from ASCII to binary.
2. Check whether the least significant bit (LSb) of AL is set, which determines whether the input is an odd or even number.
3. If the input is an odd number, add 1 to convert it to the next larger even number.
4. If the input is an even number, subtract 1 to convert it to the next smaller odd number.
5. Convert the result back to ASCII and output it to port 0 for display.
Note: This program assumes that the input number is a single digit (0-9) and does not perform any error checking. Additional code would be required to handle invalid input.
Sure! Here's a step-by-step guide on how to write a simple 8086 assembly program that meets the requirements you specified:
Step 1: Set up the program
- Open an assembly code editor, such as Turbo Assembler (TASM) or NASM.
- Start by defining the program's entry point and any required data segments. Here's an example for TASM:
```assembly
.model small
.stack 100h
.data
; Declare any required variables or constants here
.code
main proc
; Your code goes here
mov ax, @data
mov ds, ax
; Add your code here
mov ah, 4Ch
int 21h
main endp
```
Step 2: Load AL with an arbitrary number
- Use the `mov` instruction to load an arbitrary number into the AL register. For example, to load the value 15 (0Fh) into AL, you can write:
```assembly
mov al, 0Fh
```
Step 3: Check whether the number is odd or even
- Use the `test` instruction to check if the least significant bit (LSB) of the AL register is set. If the LSB is set, then the number is odd, otherwise, it is even.
- Use a conditional jump (`jz` or `jnz`) to determine the next step based on the result of the `test` instruction.
```assembly
test al, 01h ; Check if LSB is set
jz is_even ; Jump if zero (even)
; Code for odd number goes here
jmp done
is_even:
; Code for even number goes here
done:
```
Step 4: Convert the number based on its odd/even status and display it on port 0
- If the number is odd, add 1 to it to get the next larger even number, then display it on the port 0 of the trainer kit.
- If the number is even, subtract 1 from it to get the previous smaller odd number, then display it on the port 0 of the trainer kit.
Here's an example implementation:
```assembly
is_even:
; Subtract 1 to get previous smaller odd number
sub al, 01h
; Output the result to port 0
mov dx, 0000h ; Port 0 address
out dx, al
jmp done
is_odd:
; Add 1 to get next larger even number
add al, 01h
; Output the result to port 0
mov dx, 0000h ; Port 0 address
out dx, al
done:
```
Step 5: Finalize the program
- Add any necessary instructions to exit the program gracefully.
- In the provided example, the program uses the DOS interrupt 21h to exit the program cleanly:
```assembly
mov ah, 4Ch
int 21h
```
That's it! You've now written a simple 8086 assembly program that loads an arbitrary number into the AL register, checks if it's odd or even, and converts it accordingly before displaying the result on port 0.
Note: The example assumes you are using the TASM syntax. If you are using NASM or a different assembler, the syntax may vary slightly. Please consult the documentation of the specific assembler you are using.