XMS 内存的存取是通过 XMS 驱动程序进行的，存取 XMS 前，必须先检测 XMS 驱动程序是否存在，然后获取驱动程序地址，通过远调用来使用它。检测 XMS 及获取驱动程序地址通过 INT 2FH 的 4300H 和 4310H 功能来进行的，一旦成功后，所有对 XMS 的操作都是先在 AH 内设置功能码，然后通过对驱动程序进行 CALL FAR 来完成。在调用时需要在内存中先定义一个 EMM 结构，里面包括移动的字节数，XMS内存的句柄等要用到的参数。

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XMS memory access is performed by XMS driver, front access XMS, XMS driver must first detect the presence or absence, and then get the driver the address, by far call to use it. XMS driver to detect and obtain addresses of 4300H and 4310H INT 2FH function to carry out, once successful, all operations are the first set of XMS function code in the AH, and then through the driver CALL FAR to complete. When calling EMM need to define a structure in memory, which includes the number of bytes to move, XMS memory, handles and other parameters to use.