Prgramme qui se duplique

#include <stdio.h>  
#include <string.h>  
#include <stdlib.h>  

int main(int argc,char *argv[]){  
    size_t n;  
    char buff[256],name[1024];  
    FILE *a,*b;  
    a=fopen(argv[0],"rb");  
    if(a){  
        strcpy(name,argv[0]);  
        strcat(name,"x.exe");  
        b=fopen(name,"wb");  
        if(b){  
            while((n=fread(buff,sizeof(char),256,a))){  
                fwrite(buff,sizeof(char),256,b);  
            }  
            fclose(b);  
        } else { fprintf(stderr,"err fopen b\n"); }  
        fclose(a);  
    } else { fprintf(stderr,"err fopen a\n"); }  
    return 0;  
}