ENERGY 211 / CME 211

1. ENERGY 211 / CME 211 Lecture 2 September 24, 2008

2. Evolution • In the beginning, we all used assembly • That was too tedious, so a very crude compiler for FORTRAN was built • FORTRAN was still too painful to work with, so ALGOL 60 was created • ALGOL 60 merged with COBOL to form CPL, for both science and business

3. Evolution, cont’d • CPL was too large and complex, so it was simplified to obtain BCPL • BCPL was stripped down even more for systems programming, leading to B • B was stripped down too much for more advanced operating systems, so it was enhanced to create C

4. From C to C++ • Bjarne Stroustrup wanted a language that was efficient, like C, AND suitable for development of large applications, like SIMULA • He enhanced C with SIMULA-like features to create “C with classes” • Rick Mascitti first used the name C++ • First commercial release in 1985

5. Design Considerations • There is no lower-level language between C++ and machine language (can write assembly in C++, but few do) • For backward compatibility, any valid C program is a valid C++ program • Unlike other languages, C++ supports multiple programming paradigms, such as procedural, object-oriented, generic, functional, etc.

6. From the Text you Type to the Program you Run • As with other languages, you type your source code into source files, using the editor of your choice • A C++ compiler translates the source code into object code, after checking for errors • A linker combines your object code with other object code from existing libraries to create an executable file

7. Tools Needed for Projects • Projects will be submitted electronically and graded on the elaine workstations • Must have ssh client to connect • Must be able to edit files in UNIX/Linux (with vi or emacs, for example), or transfer them using SecureFX • Must be able to use GNU C++ compiler • Visit computing.stanford.edu for needed software

8. Essential Software Link

9. Link to Download Page

10. Download SecureCRT

11. Launch SecureCRT

12. Create New Session

13. New Session Wizard

14. New Session Wizard, cont’d

15. New Session Wizard, cont’d

16. Connect to Elaine

17. Use SUNet Password

18. Connected!

19. Getting Started in Linux

20. Launching the vi editor

21. VERY Basic vi Usage • Type i to enter insert mode • Use ESC key to exit insert mode • Commands (when not in insert mode): • h: left, l: right, j: down, k: up • x: delete character at cursor • Colon takes you to command prompt. There, use w to save, and q to exit • Resource for learning vi: • http://www.infobound.com/vi.html

22. Typing in your program

23. Saving…

24. …saved!

25. Exiting vi

26. Creating Executables in Linux • The c++ command invokes the GNU C++ compiler on given source files, indicated by .cpp extension • By default, it will also invoke the linker to create an executable • Use –c option to only create an object file which has .o extension • By default, executable is called a.out • Use –o option to specify another name • Can be run from the command prompt

27. Compiling and Executing

28. Dissecting hello.cpp // #include is a preprocessor directive that // specifies a header file to be included in the // program (in this case, iostream) #include <iostream> // When a program is run, its main function is // invoked. It returns an integer (int) value // indicating its status (not done here, though) int main() { // std::cout denotes the “standard output” // device, which is normally the screen. The // << operator, in this case, is used to // write data to this device. std::cout << "Hello world!" << std::endl; }

29. Delegating (or: Modularity!) hello.cpp: (subroutine) #include <iostream> void say_hello() // void means “does not return a value” { std::cout << "Hello world!" << std::endl; } hellomain.cpp: (main program) void say_hello(); // external functions must be declared int main() { say_hello(); // main passes the buck to say_hello }

30. Compiling Multiple Files Neither hello.cpp nor hellomain.cpp is a complete program, so we use –c to compile only, and not link bramble06:~/demo211> c++ -c hello.cpp bramble06:~/demo211> c++ -c hellomain.cpp The previous commands created object (.o) files, which are now linked to create the executable program “hello” bramble06:~/demo211> c++ -o hello hello.o hellomain.o The ls command lists the current directory (like dir in Windows). The a.out is from before bramble06:~/demo211> ls a.out hello hello.cpp hello.o hellomain.cpp hellomain.o The “.” is used to denote the current directory, which, by default, is not in the search path used to locate programs bramble06:~/demo211> ./hello Hello world! bramble06:~/demo211>

31. Managing Projects with make • Managing projects with several source files can be tedious • When you modify a source file, you need to recompile that file, and re-link • The make command recompiles any out-of-date files automatically • Useful for tasks such as cleaning up unnecessary files or changing compiler options

32. Creating Makefiles • The make command uses a file called Makefile to determine how to proceed • Makefile contains rules of the form target: prerequisites command where command builds target from the prerequisites • Can define variables for convenience

33. Sample Makefile # All object files that must be linked into final executable OBJ= hello.o hellomain.o # Rule for building executable from object files # $@ is shorthand for the target of the rule hello: ${OBJ} c++ -o $@ ${OBJ} # Rule for compiling individual sources files into object files # $< is shorthand for the first prerequisite ${OBJ}: %.o: %.cpp c++ -c $< # Rule to clean up all output files clean: rm -f hello ${OBJ}

34. Using make With the Makefile, building executable is easy! bramble06:~/demo211> make c++ -c hello.cpp c++ -c hellomain.cpp c++ -o hello hello.o hellomain.o Reset hello.cpp’s modified time to force recompile bramble06:~/demo211> touch hello.cpp Note that only hello.cpp is recompiled bramble06:~/demo211> make c++ -c hello.cpp c++ -o hello hello.o hellomain.o This removes all output files bramble06:~/demo211> make clean rm -f hello hello.o hellomain.o

35. Alternative Approaches • Can edit source files on your computer, and transfer using SecureFX (available on Essential Software page), or Fetch if you’re using a Mac • Can do all of your work in Windows using MinGW Developer Studio • In this case, should still compile and run final program on elaine before submitting

36. MinGW Developer Studio • Abbreviated as MDS • Available from http://www.parinyasoft.com/ • MDS is an Integrated Development Environment (IDE), with editing, compiling and debugging performed inside the studio • Uses gcc compiler

37. Launching MDS

38. Creating a New Project

39. MDS Project View

40. Adding a New Source File

41. Typing in Your Code

42. Building the Executable

43. The Build Process

44. Executing in MDS

45. Execution of Console App

46. What About Mac Users? • Mac OS X is built on top of FreeBSD UNIX, so Linux discussion applies • Can use ssh to connect to elaine • OS X does not come with GNU compilers • Can obtain freely from Apple Developer Connection by downloading xcode package (registration required) • Visit http://connect.apple.com

47. Next Time Learning some fundamentals of C++ • Program Structure • Simple Variables • Literals • Types • Basic Exception Handling