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     Name
          intdosx - Invokes a DOS system call.

     Syntax
          #include <dos.h>

          int intdosx(inregs, outregs, segregs)
          union REGS *inregs;
          union REGS *outregs;
          struct SREGS *segregs;

     Description
          The intdosx function invokes the DOS system call specified
          by register values defined in inregs and returns the effect
          of the system call in outregs. The REGS and SREGS unions are
          described in the reference page for int86x. Unlike the
          intdos function, intdosx accepts segment-register values in
          segregs, letting programs that use long-model data segments
          or far pointers specify which segment or pointer should be
          used during the system call. The inregs and outregs
          arguments are unions of type REGS. The segregs argument is a
          structure of type SREGS. These types are defined in the
          include file dos.h.

          To invoke a system call, intdosx executes an INT 21H
          instruction. Before executing the instruction, the function
          copies the contents of inregs and segregs to the
          corresponding registers. Only the DS and ES register values
          in segregs are used. After the INT instruction returns,
          intdosx copies the current register values to outregs and
          restores DS. It also copies the status of the system carry
          flag to the cflag field in outregs. If this field is
          nonzero, the flag was set by the system call and indicates
          an error condition.

          The intdosx function is used to invoke DOS system calls that
          take an argument in the ES register, or that take a DS
          register value different from the default data segment.

     Return Value
          The intdosx function returns the value of the AX register
          after the system call is completed. If the cflag field in
          outregs is nonzero, an error has occurred; in such cases,
          _doserrno is also set to the corresponding error code.

     See Also
          bdos(DOS), FP_SEG(DOS), intdos(DOS), segread(DOS)

     Notes
          Segment values for the segregs argument can be obtained by
          using either the segread function or the FP_SEG macro.

     Example
          #include <dos.h> #include <stdio.h> #include <direct.h>

          union REGS inregs, outregs; struct SREGS segregs; char
          buffer[51], buf2[51];    /* Buffers for directory names */
          char far *dir = "\\newdir";   /* Directory to create */ char
          *result1, result2;

          main() {
                  result1 = getcwd(buffer,50);
                  printf("Current working directory is =%s\n",
          buffer);

                  mkdir(dir);
                  inregs.h.ah = 0x3B;          /* Change directory
          function */
                  inregs.x.dx = FP_OFF(dir);   /* File name offset */
                  segregs.ds = FP_SEG(dir);    /* File name segment */
                  intdosx(&inregs,&outregs,&segregs);
                  result1 = getcwd(buf2,50);

                  printf("Changed working directory is =%s\n", buf2 );
                  result2 = chdir(buffer);     /* Change back */
                  result1 = getcwd(buf2, 50);

                  printf("Changed to original working directory
          =%s\n", buf2); }

          First, this program gets and displays the name of the
          current directory and creates a directory named  newdir  on
          the current drive. Then it invokes DOS system call 3BH
          (change directory) using intdosx to change the current
          working directory to newdir.  Finally, it restores the
          original directory as the current working directory.

                                                (printed 6/18/89)