CPS120: Introduction to Computer Science

1. CPS120: Introduction to Computer Science Compiling Your First Program

2. Compilers • An engine that works on your behalf to process instructions and allow you to deal with various basic rules of the language • The compiler’s job is to make sure you follow the rules, to require that you provide enough information that the compiler can translate you instructions into languages the components can understand

3. Compilers Available • Products range from freeware compilers to work environments designed for commercial application development • Borland C++ compiler • CodeWarrior • IBM Visual Age C++ • Microsoft Visual C++ • GNU freeware • DJGPP freeware (www.delorie.com/djgpp/ )

4. Compilation Process • Get the set of instructions from you • Review the instructions to see if they violate the rules (syntax) of the language • If all the rules are obeyed, create a working file in the language of the computer (machine language) • Attach to the working file full instructions for any shortcuts you may have used (linkage) • Assemble a final file in machine language

5. Compiler Files • Source code • Linked/Library file • Object file • Executable file

6. Source Code • The set of instruction that you will develop on your own for processing by the compiler

7. Executable Files • A machine-language executable file created when the compilation process is complete • All that is needed to run the program • Not human-readable • Has the extension .EXE • Stored in binary form • Copies may be distributed (portable) • Known as an application

8. Compiling and Debugging • Executable code will not be created until you correct all of the syntax errors in your source code • Then the fun (with logic errors) begins

9. Creating Source Code Files Actually Compiling a Program

10. Creating Source Code • Programmers spend most of their time with source code files • Need to be comfortable with an editor that creates ASCII text files • 7-bit representation of all keyboard character • Don’t use a word processor • If an editor in an environment is available, use that, it provides more sophisticated tools

11. Using the Editor • Save often because there is no autosave in Visual C++ • The editor will do matching of delimiters and intelligent indentation

12. C++ Usages & Conventions • C++ is absolutely case sensitive • For Instance: A is 97 in ASCII and a is 65 • Remember: in ASCII {, [, and ( are not equivalent • No keywords in ANSI standard are even partially uppercase • ‘While’ is not a keyword, ‘while’ is • Be careful if you define new keywords • The most common practice in C+++ is to use small letters of the first part of a variable name and capitals for the rest of it

13. Comments • Document what is happening, why it is happening and other issues • Commentary is ignored by the compiler • C++ has inline, block and documentary comments • Inline comments are within line of code • Use the // symbols • Block comments are long comments delimited with /* and */

14. Scope Delimiters • A symbol or pair of symbols used to define a region or area which is considered a locale • In programming, many structures need to have their scope defined because they should not affect the entire program • In C++, the symbols ‘{‘ and ‘}’ are used

15. Literals • Literals are system commands and other pieces of information that the compiler doesn’t understand, and therefore, takes your word for them • In C++, literals are enclosed in straight double quotes "" which is the shift of the apostrophe

16. Columns and White Space • Modern programming languages are free form with delimiters instead of columns to determine the end of instructions • The ; (semi-colon) is the delimiter used in C++ • Use tabs, indents, and blank lines in any manner that makes code easier to understand • Many programming instructions become subordinate to other instructions due to scope and other restrictions. Formatting code to reflect this makes it easier to read

17. Variables • Variables or identifiers are used to hold information • Usually mixed case with the first letters small and the rest starting with a capital • e.g. theWeight

18. Color Coding in Visual C++ Editor • Comments are green and are ignored by the compiler • All ANSI keywords are coded in blue • Other code is in plain black • Compiler keywords like cin and cout are also shown in black

19. Setting Up a Visual C++ Workspace • Left-click START • In the program section, select Visual Studio or Visual C++ (depending on what is installed) • Left click on the Visual C++ icon to load the environment • Create a new work area by choosing FILE/NEW • Choose FILES tab • Click on the C++ Source File to reach the editor • Add a filename and directory before continuing • e.g. c:/cppFun/myFirstCpp

20. Setting Up a Visual C++ Workspace • Create the directory with START / EXPLORE • Double-click the drive letter • Choose FILE, NEW FOLDER • Left click on FOLDER • Change new folder to cppFUN • Close Explorer with the X • Back in Visual C++, type myFirstCpp in the file box • Click OK and get back to the main edit screen

21. Setting Up a Visual C++ Workspace • Enter the source code • After entering the program, FILE then SAVE

22. Why Create New Subdirectories? • You should always use subdirectories to store your files. Visual C++ creates quire a few work files when it generates the executable file for you source code, and they will be easy to dispose of if you keep everything together in one convenient place. • Under no circumstances should you use the root (C:\) directory except on a floppy disk (A:\).

23. Running the Program • Press the REBUILD ALL button. It has two arrows in a box • Press the RUN button. It is a red exclamation point

24. Disk Space Issues • Text files are insignificant in terms of space • However, six other files are created every time something is compiled; some get around 95% full • Highlighting the disk in are 3 or 4 times larger than the source • You can delete anything but the file with the .cpp suffix; everything else can be recreated

25. Recompiling • Open the file by going the file you stored it in and double clicking on it • Scan the source code for obvious errors before attempting to compile • Attempt to compile using the COMPILE button or choosing the first option on the BUILD menu • Answer Yes to use the default project workspace • The lower window will be active and the compile will occur • Note the number of errors and warnings • These need to be dealt with before executable code is created

26. Working in a Lab Environment • The following issues are magnified working in a laboratory environment: • Viruses • Scan disks transferring between the lab and home • Plagiarism • Beware of shoulder surfing, temp directories, shared directories, discarded print and new print • Name things vaguely and delete what you are done with • Theft • Take your floppies and Zip Disks with you • Malicious mischief