about fork()

i am learning the kernel,the fork() ,i have some questions,and read some from the net,but not very know about it

the source:

#include

#include

#include

void main()

{

int i;

int p_id;

printf("aaa");

p_id=fork();

if(p_id==0)

{

for(i=1;i<3;i++)<br />
{ printf("this is child process\n"); }

}

if(p_id==-1)

{

printf("fork new process error!\n");

}

if(p_id==0)

{

printf("iii");

for(i=1;i<3;i++)<br />
{ printf("this is parent process\n" ); }

}

printf("bbb");

}

yanj@yanj-desktop:~/lianxi/chapter2$ ./forktest

aaathis is child process

this is child process

iiithis is parent process

this is parent process

I know fork() copy the two same program to child,parent process,

why can show "aaa",cannot "bbb"