os_kernel_lab/related_info/lab0/lab0_ex4.md

#README
Try below command
```
gcc -g -m32 -I. lab0_ex4.c 2>&1|tee make.log
```
If you get gcc's error, try to read make.log and fix the bugs.

If gcc successed, then you will get a.out. 

Try to answer below question.