Header File 

process.h  

Category 

Process Control Routines 

Prototype 

unsigned long _beginthread(void (_USERENTRY *__start)(void *), unsigned __stksize, void *__arg); 

Description 

Starts execution of a new thread.

The size of its stack in bytes is stack_size; the stack is allocated by the operating system after the stack size is rounded up to the next multiple of 4096. The thread is passed arglist as its only parameter; it can be NULL, but must be present. The thread function should terminate by simply returning; the _endthread. function will be called automatically. The _endthread function will automatically close the handle, and set the return value of the thread to zero. 

Either this function or _beginthreadNT must be used instead of the operating system thread-creation API function because _beginthread and _beginthreadNT perform initialization required for correct operation of the runtime library functions. 

This function is available only in the multithread libraries. 

Return Value 

_beginthread returns the handle of the new thread. The return value is a standard Windows handle that can be used in operating system API's such as SuspendThread and ResumeThread. 

On error, the function returns -1, and the global variable errno is set to one of the following values:

Also see the description of the Win32 API GetLastError, in the MSDN Library. 

Example  

/*  Use the -tWM  (32-bit multi-threaded target) command-line switch for this example  */
#include <stdio.h>
#include <errno.h>
#include <stddef.h>     /* _threadid variable */
#include <process.h>    /* _beginthread, _endthread */
#include <time.h>       /* time, _ctime */
void thread_code(void *threadno)
{
    time_t t;
    time(&t);
    printf("Executing thread number %d, ID = %d, time = %s\n",
        (int)threadno, _threadid, ctime(&t));
    
}
    
void start_thread(int i)
{
    int thread_id;
#if     defined(__WIN32__)    
    if ((thread_id = _beginthread(thread_code,4096,(void *)i)) == (unsigned long)-1)
#else
    if ((thread_id = _beginthread(thread_code,4096,(void *)i)) == -1)
#endif
    {
        printf("Unable to create thread %d, errno = %d\n",i,errno);
        return;
    }
    printf("Created thread %d, ID = %ld\n",i,thread_id);
}
int main(void)
{
    int i;
    for (i = 1; i < 20; i++)
        start_thread(i);
    printf("Hit ENTER to exit main thread.\n");
    getchar();
    return 0;
}

Portability