关注
(1) dynamic loading
load program进memory时，优先load main()所在的memory page。其他page根据program是否会调用该page上存的function决定是否load进memory
(2) dynamic linking和static linking
* static linking treats the libraries as if they are normal *.obj files. During linking stage, the library code are also combined into the binary.
* dynamic linking will place a "stub" in each library routine reference. The "stub" is a small piece of code which indicates how to access the corresponding library routine.
