# ! $Source$ ! $State$ ! $Revision$ ! Declare segments (the order is important). .sect .text .sect .rom .sect .data .sect .bss .sect .text ! Say whether a given file descriptor number refers to a valid open file ! descriptor. .define __sys_isopen __sys_isopen: mov bx, sp mov bx, 2(bx) mov ax, 0x4400 int 0x21 sbb ax, ax inc ax ret