2014-10-05 10:06:14 +00:00
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mov ah, 0x0e ; tty mode
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2014-10-05 10:03:44 +00:00
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2018-09-21 18:24:55 +00:00
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mov bp, 0x8000 ; this is an address far away from 0x7c00 so that we don't get overwritten
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mov sp, bp ; if the stack is empty then sp points to bp
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; if we push (0x8000 - 0x7c00) bits (0x400 or 1,024 bits), we will start to write over
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; the bootloader. so, don't do that!
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2014-10-05 10:03:44 +00:00
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2018-09-21 18:24:55 +00:00
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; still in 16-bit mode, so these each push 16 bits onto the stack.
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2014-10-05 10:03:44 +00:00
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push 'A'
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push 'B'
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push 'C'
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; to show how the stack grows downwards
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2018-09-21 18:24:55 +00:00
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mov al, [0x7ffe] ; 0x8000 - 16 bits
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2014-10-05 10:03:44 +00:00
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int 0x10
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2018-09-21 18:24:55 +00:00
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mov al, [0x8000] ; this is a null byte - it's the top of the stack
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int 0x10
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mov al, [0x7ffa] ; 0x8000 - 48 bits. lower in memory
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2014-10-05 10:03:44 +00:00
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int 0x10
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; recover our characters using the standard procedure: 'pop'
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; We can only pop full words so we need an auxiliary register to manipulate
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; the lower byte
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pop bx
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mov al, bl
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int 0x10 ; prints C
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pop bx
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mov al, bl
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int 0x10 ; prints B
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pop bx
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mov al, bl
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int 0x10 ; prints A
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; data that has been pop'd from the stack is garbage now
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mov al, [0x8000]
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int 0x10
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jmp $
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times 510-($-$$) db 0
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dw 0xaa55
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