Function 26h (38)        Create Program Segment

    Creates a new Program Segment Prefix (PSP).

       On entry:      AH         26h
                      DX         Segment address of new PSP
                      CS:0       PSP to copy information from

       Returns:       Nothing

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    This function creates a new Program Segment Prefix (PSP), in order to
    prepare a separately loaded subprogram (i.e., overlay), for execution.
    The PSP at the start of the current program's code segment is copied
    into the first 256 bytes of the new segment specified in DX. The new
    PSP is updated with the current Int 22h, Int 23h, and Int 24 interrupt
    handlers. Memory size information at location 06h of the new PSP is
    updated to reflect available memory.

       Notes:         This function has been superseded by the EXEC
                      function (Function 4Bh) in versions 2.0 and later of
                      DOS; this function should not be used.