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> Example 1. - A thread creation under C/2
> 
> This first simple Example 1. shows how to create one new thread in C under OS/2 32-bit which has the number 2, called Thread Identifier (TID) 2. For any C environment there have to considered special conditions like the condition for the stack space. The main program starts with TID 1. 
> 
> To create the thread here it is used the C library function _beginthread.
> 
> Definition of _beginthread:
> 
> #include <stdlib.h>     /* also defined in <process.h> */
>  
> int _beginthread(void (*start_address) (void *),
>                       (void *)stack,
>                       unsigned stack_size,
>                       void *arglist);
>  
>  
> Language Level: Extension 
> 
> The _beginthread function creates a new thread. It takes the following arguments: 
> 
> start_address:
> 
> This parameter is the address of the function that the newly created thread will 
> execute. When the thread returns from that function, it is terminated 
> automatically. You can also explicitly terminate the thread by calling _endthread. 
> 
> stack:
>  
> This parameter is ignored, but is retained to ease migration of C/2 programs.  
> The C/2 compiler requires the second parameter to be the address of the bottom 
> of the stack that the new thread will use. Because the OS/2 operating system 
> automatically takes care of stack allocation, the parameter is not needed. 
>  
> stack_size:
> 
> The size of the stack, in bytes, which is to be allocated for the new thread.  
> The stack size should be a nonzero multiple of 4K and a minimum of 8K(!). Memory 
> is used when needed, one page at a time.  
> 
> arglist:
>  
> A parameter to be passed to the newly created thread. It is the size of a 
> pointer, and is usually the address of a data item to be passed to the new 
> thread, such as a char string. It provides _beginthread with a value to pass to 
> the child thread. NULL can be used as a placeholder. 
>  
> The function that the new thread will perform must be declared and compiled 
> using _Optlink linkage. 
> 
> An alternative to this function is the OS/2 DosCreateThread API. If you use 
> DosCreateThread, you must also use a #pragma handler statement for the 
> thread function to ensure proper C exception handling. You should also call the 
> _fpreset function at the start of the thread to preset the 387 control status word 
> properly. The use of DosCreateThread requires the use of _endthread to 
> terminate the thread. 
> 
> Note:  When using the _beginthread and _endthread functions, you must specify 
> the /Gm+ compiler option to use the multithread libraries. 
> 
> If successful, _beginthread returns the thread ID number of the new thread. It 
> returns -1 to indicate an error. 
> 
>  
>  Example of _beginthread :
>  
>  
>  /************************************************************************
>  
>  This example uses _beginthread to start a new thread bonjour, 
>  which prints Bonjour! five times and then implicitly ends itself. The 
>  program then prints a statement indicating the thread identifier number 
>  for bonjour. 
> 
>  Note:  To run this example, you must compile it using the /Gm+ 
>  compiler option for C/2
> 
>                                                                         
>  ************************************************************************/
>   
> 
>  #define INCL_DOS
>  #define INCL_DOSERRORS /* DOS error values */
>  #include <os2.h>
>  #include <stdio.h>
>  #include <stdlib.h>
>  
>  static int wait = 1;
>  
>  void bonjour(void *arg)
>  {
>     int i = 0;
>  
>     while (wait)
>             /* wait until the thread id has been printed */
>        DosSleep(0l);
>  
>     while ( i++ < 5 )
>        printf("Bonjour!\n");
>  }
>  
>  int main(void)
>  {
>     unsigned long tid;
>  
>     tid = _beginthread(bonjour, NULL, 8192, NULL);
>  
>     if ( tid == -1 )
>     {
>        printf("Unable to start thread.\n");
>        exit(-1);
>     }
>     else
>     {
>        printf("Thread started
>                with thread identifier number %d.\n", tid);
>        wait = 0;
>     }
>  
>     DosWaitThread( &tid, DCWW_WAIT );
>                 /* wait for thread bonjour to end */
>                 /*  before ending main thread      */
>  
>     return 0;
>  
>  /* The expected output
>         (with possible thread id number) is: */
>  
>        Thread started with thread identifier number 2.
>        Bonjour!
>        Bonjour!
>        Bonjour!
>        Bonjour!
>        Bonjour!                                                  */
>  
>  }
>  
>  
> Remarks:
> 
> The first action of the program is to print the message in the main program:
> 
> "Thread started with thread identifier number ...". Because the thread(i.e. program
> execution) runs parallel(!) with the created thread of the routine bonjour, a control
> variable "wait" let run the while loop for DosSleep until the message from the main 
> program is printed. 
> 
> Then the thread 2 of the routine bonjour can start to print the message loop 5 times.
> The execution runs back to the main program. Because the execution of this
> printing can last it must be avoided that the return of the main program ends the running
> thread 2 of the routine bonjor. Therefore there is the call of DosWaitThread, which 
> holds the main program until thread 2 (connected via the TID address) ends.
> 
> The option DCWW_WAIT in DosWaitThread means:
> 
> The current thread waits until a thread ends. If a thread has already ended, the call
> returns immediately with the TID.  
> 
> One can define a return code like this:
> 
> rc = DosWaitThread(&tid, DCWW_WIT)
> 
> If (rc != NO_ERROR) {
> 
> printf ("DosWaitThread error: return code = %\n", rc);
> 
> }
> 
> 
> The return code of DosWaitThread are:
> 
> 0 ---  NO_ERROR
> 
> 95 --  ERROR_INTERRUPT
> 
> 294 -  ERROR_THREAD_NOT_TREMINATED
> 
> 309 -  ERROR_INVALID_THREADID
> 
> 
> In a later lession the OS/2 API DosWaitThread will defined more detailed. 
> 
>

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