Си. POSIX и WinApi

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <pthread.h>
 
#define N 1000
int a [N][N] , b [N][N] , c [N][N] ;
void * ThreadFunction ( void *id )
{
int iid ;
iid=*(int *) id ;
for ( int i=iid*N/4   ; i<(iid+1)*N/4   ; i++)
 
    for ( int j=0  ; j<N  ; j++){
        a[i][j]=0;
        for (int v=0; v<N; v++) {
            a[i][j] += b[i][v]*c[v][j];
        }
    }
return NULL ;
}
int main ( int argc , char *argv [ ] )
{
 
for ( int i=0 ; i<N ; i++)
for ( int j=0 ; j<N ; j++)
{
b[i][j]=1;
c[i][j]=2;
}
pthread_t thread [ 4 ] ;
int ID [ 4 ] = { 0 , 1 , 2 , 3 } ;
pthread_create(&thread [ 0 ] , NULL , ThreadFunction , ( void *)&ID[ 0 ] ) ;
pthread_create(&thread [ 1 ] , NULL , ThreadFunction , ( void *)&ID[ 1 ] ) ;
pthread_create(&thread [ 2 ] , NULL , ThreadFunction , ( void *)&ID[ 2 ] ) ;
pthread_create(&thread [ 3 ] , NULL , ThreadFunction , ( void *)&ID[ 3 ] ) ;
pthread_join ( thread [ 0 ] , NULL ) ;
pthread_join ( thread [ 1 ] , NULL ) ;
pthread_join ( thread [ 2 ] , NULL ) ;
pthread_join ( thread [ 3 ] , NULL ) ;
printf ( "Result: \n" ) ;
/*for ( int i=0; i<N; i++)
{
    for (int j=0; j<N; j++){
printf ( "%d " , a [ i ][ j ] ) ;}
printf("\n");
}
*/
return ( 0 ) ;
}