基于“元神”操作系统开发软件

【开发流程】

1. 用FASM汇编语言等编写代码。例如，将下面的demo1或demo2复制保存为demo.asm

2. 编译生成可执行文件。例如，执行命令“fasm.exe demo.asm demo.bin”以生成可执行文件demo.bin

3. 将可执行文件复制到元神系统可访问的磁盘。例如，将demo.bin复制到HOS.BIN所在U盘的根目录

4. 启动元神系统并运行可执行文件。例如：用元神系统所在U盘开机启动系统，执行“ZX demo.bin”

【demo1】

    use32

    START:
        pusha
        
        call demo1
        
        popa
        iret


    ;print string at specified coordinate, e.g y=10 and x=2
    demo1:
        pusha
        mov esi,hello_text
        mov ebx, 10
        mov ecx, 2
        call print_string
        popa
        ret

    ;print string
    ;input:
    ;	esi: address to string
    ;	ebx: y position to print
    ;	ecx: x position to print
    print_string:
        pusha
        xor eax, eax
        imul edi, ebx, 80*2
        add edi, ecx
        add edi, ecx
        mov ah, 0x0F
    .next_char:
        lodsb
        cmp al, 0
        je .end
        mov word [gs:edi], ax
        add edi, 2
        jmp .next_char
        .end:
        popa
        ret
 
    hello_text db 'Hello world!',0

【demo2】

    use32

    START:
        pusha
        
        call demo2
        
        popa
        iret

    cursor_x equ 0x02004B10
    cursor_y equ 0x02004B12

    ;print string at current cursor position which is readed from OS
    demo2:
        pusha
        
        mov esi,hello_text
        movzx ebx, word [fs:cursor_y]
        movzx ecx, word [fs:cursor_x]
        call print_string
        
        add word [fs:cursor_y], 1
        
        popa
        ret

    ;print string
    ;input:
    ;	esi: address to string
    ;	ebx: y position to print
    ;	ecx: x position to print
    print_string:
        pusha
        xor eax, eax
        imul edi, ebx, 80*2
        add edi, ecx
        add edi, ecx
        mov ah, 0x0F
    .next_char:
        lodsb
        cmp al, 0
        je .end
        mov word [gs:edi], ax
        add edi, 2
        jmp .next_char
        .end:
        popa
        ret

    hello_text db 'Hello world!',0