Function            isrealtimeclock - is a real time clock installed

  Syntax              int isrealtimeclock(void);

  Prototype in        ibm.h

  Remarks             isrealtimeclock() detects if a real time clock is
                      installed.

  Return value        returns 1 if a real time clock is installed, 0 if
                      it is not, and -1 if this function is not
                      supported.

  Note                the 1/10/86 XT BIOS returns an incorrect value for
                      this function, so if the machine is an IBM XT or
                      compatible with a BIOS date of 1/10/86, do not use
                      this function.

  Example             #include <ibm.h>

                      main()
                      {
                           printf("real time clock: ");
                           switch (isrealtimeclock()) {
                                case -1: printf("Error");  break;
                                case  0: printf("No");  break;
                                case  1: printf("Yes");  break;
                      }