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  In the PC/XT/AT family, the 16 bytes starting at 0040:00F0H are reserved
  as an intra-application communication area (ICA). This data area provides
  an area of RAM at a known address that an application can use for sharing
  data among separate program modules. In the PS/2 BIOS, however, the ICA is
  no longer documented.

  Few applications actually use the ICA because the amount of RAM is so
  small and because the data within the ICA can be unexpectedly modified
  when more than one program uses it. If you do write a program that uses
  the ICA, we recommend that you include a checksum and also a signature so
  that you can ensure that the data in the ICA is yours and that it has not
  been changed by another program.

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  WARNING:
    The ICA is definitely located in the 16 bytes from 0040:00F0H through
    0040:00FFH. A typographic error in some editions of the IBM PC Technical
    Reference Manual places it at 0050:0000H through 0050:00FFH. This is
    incorrect.
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