Category : Utilities for DOS and Windows Machines
Archive   : AT-CLOCK.ZIP
Filename : FIXCLOCK.C

Output of file : FIXCLOCK.C contained in archive : AT-CLOCK.ZIP
/* fixclock.c
* This program corrects the system time upon boot up. The system time is
* normally obtained from the cmos clock. This clock is crystal controlled
* but may exhibit an error of several minutes per month anyway. A knowledge
* of this error allows it to be compensated for and corrected.
* The program is designed to be called from the autoexec.bat file upon boot
* up. An example of the proper entry in the .bat file is as follows:
* fixclock tz=cst6cdt 23:13:45 10-25-88 -213 L
* The first parameter sets the timezone. It consists of tz= followed by a
* three letter abbreviation of the standard timezone: pst, mst, cst, or est.
* This is followed by a number indicating the number of hours between the
* local time and GMT, followed by the abbreviation for daylight savings time,
* pdt, mdt, cdt, or edt if it is observed in your area. If it is not observed
* then don't append it. For instance, in parts of Indiana you would have a
* timezone parameter that looks like this: tz=cst6
* The next two entries are the time and date the cmos clock was properly set.
* These values are obtained from the clock statistics produced by the program
* clockerr, when the q parameter is used.
* The next entry is also obtained from the clock statistics report and is a
* signed integer representing the number of seconds gained or lost by the
* cmos clock per month. If the clock looses time then it is negative.
* The last entry on the command line determines whether the system will
* display local time or GMT. If you wish local time use an L here. For GMT
* use a G. If you choose the local option then the system will always display
* the local time and will correct for daylight savings time when it is in
* effect without any action on your part.


#define MONTH 2419200.0 /* Seconds in a month (28 days) */
#define LCL 1
#define GMT 0

void main(int argc, char *argv[]);
void set_time(time_t *time, int local);
time_t clock_started(char *argv[]);

void main(int argc, char *argv[])
int i;
time_t error, cmos_time, new_time;
double elapsed;

* Check for proper number of command line arguments (5)
if(argc != 6)
puts("Incorrect Number Of Parameters...");

* The case of the first argument doesn't matter.
for(i=0; *(argv[1]+i); i++)
*(argv[1]+i)=toupper( *(argv[1]+i) );

* Put the time zone info which is the first argument, into the
* program environment. Next, set the global timezone variables
* to the specified values.

* time(&cmos_time) returns the time kept by the cmos clock, this is
* converted to seconds since the epoch. clock_started(argv) returns
* the time when the cmos clock was set, converted to seconds since
* the epoch, the time when the cmos clock was set is obtained from
* entries on the command line. The clock error is also obtained from
* the command line. new_time represents the corrected time in seconds
* since the epoch and is used to set the system time.
elapsed = time(&cmos_time) - clock_started(argv);
error = atoi(argv[4]);
new_time = cmos_time - elapsed * error/MONTH;
case 'L':
* Sets the correct local time as requested by the "L"
* on the command line.
set_time(&new_time, LCL);

case 'G':
* Sets the correct Greenwich Mean Time by adding the
* value of the timezone variable to the corrected time.
new_time += timezone;
set_time(&new_time, GMT);

time_t clock_started(char *argv[]) /* clock value when first set */

* Command line values representing the time at which the cmos clock was
* set are retrieved and converted to integer values to fill the structure
* systime. This structure is then passed to mktime() so that the return
* value is a variable of type time_t.
struct tm systime;
systime.tm_hour = atoi(argv[2]);
systime.tm_min = atoi(argv[2]+3);
systime.tm_sec = atoi(argv[2]+6);
systime.tm_mon = atoi(argv[3])-1; /* MSOFT definition idiosyncracy */
systime.tm_mday = atoi(argv[3]+3);
systime.tm_year = atoi(argv[3]+6);
systime.tm_isdst = 0; /* Command line value is standard time. */
return mktime(&systime);

void set_time(time_t *time, int local) /* Set the correct system time. */
struct tm *time_date, *dst;
struct dostime_t to_dostime;
struct dosdate_t to_dosdate;

* Convert the correct time to a structure of type tm, then examine
* dst->is_dst to see if daylight savings time is in effect and observed
* and to see if local time format is desired. If so then add an hour to
* the correct time which otherwise is standard time.
dst = localtime(time);
if(dst->tm_isdst && daylight && local)
*time = *time + 3600; /* DST and local time in effect */

* The corrected time is converted to a structure of type tm. The elements
* of this structure are used to assign values to the structure to_dostime
* and to_dosdate. These two structures are then used to set the system
* date and time.
time_date = localtime(time);
to_dostime.hour = time_date->tm_hour;
to_dostime.minute = time_date->tm_min;
to_dostime.second = time_date->tm_sec;
to_dostime.hsecond = 50; /* In lieu of rounding. */
_dos_settime(&to_dostime); = time_date->tm_mday;
to_dosdate.month = time_date->tm_mon + 1;
to_dosdate.year = time_date->tm_year + 1900;
to_dosdate.dayofweek = time_date->tm_wday;

  3 Responses to “Category : Utilities for DOS and Windows Machines
Archive   : AT-CLOCK.ZIP
Filename : FIXCLOCK.C

  1. Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!

  2. This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.

  3. But one thing that puzzles me is the “mtswslnkmcjklsdlsbdmMICROSOFT” string. There is an article about it here. It is definitely worth a read: