Program 1: Hello World

 **Program 1: Hello World**

```assembly

.model small

.stack 100h

.data

    message db 'Hello, World!', '$'

.code

    main proc

        mov ah, 09h          ; DOS function to print string

        lea dx, message      ; Load effective address of message

        int 21h              ; Call DOS interrupt

        mov ah, 4Ch          ; Exit program

        int 21h

    main endp

end main

```

Explanation:

1. `.model small` and `.stack 100h`: Memory model and stack size definitions.

2. `.data` section: Declares the data segment.

   - `message db 'Hello, World!', '$'`: Defines a null-terminated string.

3. `.code` section: Contains the main code.

   - `mov ah, 09h`: Load DOS function code for printing a string.

   - `lea dx, message`: Load effective address of the message string.

   - `int 21h`: Call DOS interrupt to print the string.

   - `mov ah, 4Ch`: Set the exit code for DOS.

   - `int 21h`: Call DOS interrupt to exit the program.