This assignment is to create a program to compute factorials using
threads and signals as event triggers. What follows is a fairly
thorough description of what different pieces of your code should
contain and precisely how signals, threads, and globals should
interact. You'll need to include quite a few headers that I discussed
in class and reiterated (in part) here.



MAIN:

The "int main" function of your program should have only about seven
lines and no other code. The first function call is to seed the random
number generator (use srand(time(NULL)) which requires stdlib.h and
time.h).  The second call is to set up a signal handler for SIGINT (or
control-c on the keyboard), and the third is to set up a signal
handler for SIGQUIT (or control-\ on the keyboard). Next is a call to
pause() (in unistd.h) inside of a loop that continues until SIGQUIT
has been performed. Lastly you'll report values computed - but this
will make more sense after you read what should be handled by SIGINT
and SIGQUIT.

seed the random number generator: srand( time(NULL) );
assign signal handler for SIGINT
assign signal handler for SIGQUIT
while(have not seen SIGQUIT)
    pause();
report all values computed
 



SIGINT and Thread Creation 

For SIGINT: Have your signal handler first create a random number
between 0 and 13. (To get a random number between 0 and 13 you can use
rand()%14). Then, the signal handler should create a worker thread and
pass the number as a character string parameter to the function (not
via a global). A note below will help you convert the integer into a
character string so that you may properly pass it to the function.
The handler should then wait for the worker thread to finish
completion before returning control back to the main program.



Thread operation:

The worker thread should compute the value of the factorial passed to
it (use atoi to convert the char string BACK). The result of this
computation should be stored globally and permanently by the worker
thread (the random number could be stored in one vector while the
factorial results could be stored in another vector).



SIGQUIT:

For SIGQUIT: Have your signal handler report the fact that sigquit has
been seen via a global variable. This is how we will exit the loop in
main containing pause().
 


 
Side Note:

To convert an integer to a string, you can use sprintf.

int value = 77; // the integer variable that I want to convert to a cstring
char buf[32];  // a buffer to be the cstring
sprintf(buf,"%d",value);   //place the value as a string into the buf

Of course, to convert a string back into an integer use:
//assume param is a char * to convert to an integer
int value = atoi(param);

//if you assume param is a void * that was passed a char *, you can use;
int value = atoi ( (char *) param );