my own os in asm

happy os kernel

[ORG 0x7C00]          ; BIOS loads bootloader at 0x7C00
[BITS 16]            ; 16-bit real mode

section .text
start:
    cli               ; Disable interrupts
    cld               ; Clear direction flag
    xor ax, ax        ; Zero out registers
    mov ds, ax
    mov es, ax
    mov ss, ax
    mov sp, 0x7C00    ; Set stack pointer
    sti               ; Enable interrupts

    call clear_screen ; Clear screen
    call print_welcome ; Print welcome message
    call set_time     ; Prompt user to set time
    call print_prompt ; Print initial prompt

command_loop:
    call read_command ; Read user input
    call process_command ; Process input
    jmp command_loop ; Repeat

; Function to clear the screen
clear_screen:
    mov ah, 0x06
    mov al, 0
    mov bh, 0x02  ; Green text on black background
    mov cx, 0
    mov dh, 24
    mov dl, 79
    int 0x10
    ret

; Function to print welcome message
print_welcome:
    mov si, welcome_msg
    call print_string
    ret

; Function to print prompt
print_prompt:
    mov si, prompt_msg
    call print_string
    ret

; Function to prompt for time
set_time:
    mov si, set_time_msg
    call print_string
    call read_command
    mov si, buffer
    call strcpy
    ret

; Function to read user command
read_command:
    mov di, buffer
    mov cx, 0
.read_loop:
    mov ah, 0x00
    int 0x16 ; Wait for key press
    cmp al, 0x0D ; Enter key?
    je .done
    mov [di], al
    inc di
    inc cx
    jmp .read_loop
.done:
    mov byte [di], 0
    ret

; Function to process command
process_command:
    mov si, buffer
    mov di, cmd_clear
    call strcmp
    jz clear_screen

    mov si, buffer
    mov di, cmd_hello
    call strcmp
    jz print_hello

    mov si, buffer
    mov di, cmd_echo
    call strcmp
    jz echo_command

    mov si, buffer
    mov di, cmd_write
    call strcmp
    jz write_command

    mov si, buffer
    mov di, cmd_run
    call strcmp
    jz run_command

    mov si, buffer
    mov di, cmd_basic
    call strcmp
    jz start_basic

    mov si, buffer
    mov di, cmd_dice
    call strcmp
    jz roll_dice

    mov si, buffer
    mov di, cmd_time
    call strcmp
    jz show_time

    ret

; Print "Hello, World!"
print_hello:
    mov si, hello_msg
    call print_string
    ret

; Echo command
echo_command:
    mov si, buffer+5 ; Skip "echo "
    call print_string
    ret

; Show stored time
show_time:
    mov si, time_msg
    call print_string
    mov si, buffer
    call print_string
    ret

; BASIC DICE ROLL COMMAND
roll_dice:
    rdtsc            ; Read time-stamp counter
    xor ax, dx       ; XOR lower and upper parts
    mov cl, 6        ; Dice sides
    div cl           ; Get remainder (0-5)
    add ah, 1        ; Ensure range 1-6
    mov bx, ax
    call print_number
    ret

; Print a number
print_number:
    mov ax, bx
    call int_to_ascii
    mov si, num_buffer
    call print_string
    ret

; Convert integer to ASCII
int_to_ascii:
    mov di, num_buffer+5
    mov byte [di], 0
    dec di
    mov cx, 10
.convert:
    xor dx, dx
    div cx
    add dl, '0'
    mov [di], dl
    dec di
    test ax, ax
    jnz .convert
    inc di
    mov si, di
    ret

; Print a string
print_string:
    mov ah, 0x0E
.loop:
    lodsb
    or al, al
    jz .done
    int 0x10
    jmp .loop
.done:
    ret

; Copy string
strcpy:
.loop:
    lodsb
    stosb
    test al, al
    jnz .loop
    ret

; String comparison function
strcmp:
.loop:
    mov al, [si]
    mov bl, [di]
    cmp al, bl
    jne .not_equal
    test al, al
    jz .equal
    inc si
    inc di
    jmp .loop
.not_equal:
    xor ax, ax
    ret
.equal:
    mov ax, 1
    ret

; Data section
data:
welcome_msg db 'Welcome to Happy OS
#                        #   ##
###  ## ### ### # #     # # # 
# # # # # # # # ###     # #  #
# # ### ### ###   #     # #   #
       #   #   ###      #  ##                                          
', 0
set_time_msg db 'Set time (HH:MM): ', 0
time_msg db 'Current Time: ', 0
basic_msg db 'Entering BASIC mode. Supported: PRINT, GOTO, INPUT, LET, IF, FOR, RND, TIMER, SOUND, DICE, TIME, END', 0
prompt_msg db 'input command> ', 0
hello_msg db 'Hello, World!', 0
cmd_clear db 'clear', 0
cmd_hello db 'hello', 0
cmd_echo db 'echo ', 0
cmd_write db 'write', 0
cmd_run db 'run', 0
cmd_basic db 'basic', 0
cmd_print db 'PRINT ', 0
cmd_goto db 'GOTO ', 0
cmd_input db 'INPUT ', 0
cmd_let db 'LET A=', 0
cmd_if db 'IF ', 0
cmd_for db 'FOR ', 0
cmd_rnd db 'RND', 0
cmd_timer db 'TIMER ', 0
cmd_sound db 'SOUND ', 0
cmd_dice db 'DICE', 0
cmd_time db 'TIME', 0
cmd_end db 'END', 0
var_A db 0
num_buffer times 6 db 0
buffer times 64 db 0
exec_buffer times 256 db 0
basic_program times 512 db 0

times 510-($-$$) db 0
    dw 0xAA55  ; Boot signature
;copyright-2025-bronze-computing-Brogan-Guthrie