02.txt

一個計算機系教授的上課講義 主要是教導學生使用C語言編寫程序

CS 1355
Intro to Programming in C
Thursday 2006.9.14 (Week 1)
Lecture Notes (at http://r638-2.cs.nthu.edu.tw/C/notes/02.txt)

Introduction (Chapter 1 continued)

- Announcements
- Compiler vs. Interpreter
- C++ and Java
- Standard I/O
- Internet

Announcements: Office hours
- Professor: (Room EECS 638)
  Mon 1pm-2pm, Thu 3pm-5pm
- TA:        (Room EECS TA room)
  Tue 10am-12pm, Wed 10am-12pm

More on Compiler vs. interpreter
- CC: C-compiler
  - compile C source code, outputs an executable file
  - run the executable file
- Shell (c-shell, bash, etc): interpreter
  - type a command (e.g., "ls")
  - get result immediately on the screen, no compilation
    ("ls" is an executable, but the shell interprets "ls" by
     calling the "loader" to run it)
    => you can find out where the executable is located, by typing
    %  which ls
    /bin/ls
    ("which" itself is a command interpreted by the shell)
    %  which which
    which: shell built-in command
    %  which vi
    /usr/bin/vi

    Note: / is the top level directory.
          /usr is the "usr" directory from the top
          /usr/bin is the "bin" directory inside "/usr"

Interpreters can do much more than shell
- example: python, an interpreted language
  % python
  >>> 
  Note: >>> is the python prompt
  >>> x = 2
  >>> y = 3
  >>> x + y
  5
  >>>
  Each line is interpreted when it is typed in.
  No need for compilation.
=> quick way to get an answer

What is C++?
- "object-oriented" extension of C
  - a different way of "packaging" data and program.
  - example: data=picture, program=to resize to x, y
- Regular C, "procedure oriented" way:
	resize(picture, 100, 200);
- in C++, "object oriented" way
	picture.resize(100, 200);
- so, why is it useful?
  reason 1: put related program code together, better organization.
    Example, 
      picture.resize(...)
      picture.rotate(...)
      picture.clip(...)
      picture.mirror(...)
  reason 2: inheritance
    Example, 
      initially, you write programs for black-and-white pictures.
      later, you make color pictures.
      Conceptually, resize(), rotate(), clip(), ... are the same for user
    Inheritance:
      lets color pictures use the same function as black-and-white,
      also allows color pictures to use new functions
        colorPicture.setSaturation(...)  眒︹緻