Tools:

• Editor: Create one or more source files
• Containing the program in human-readable form
• Compiler: Convert the source files to object files
• Containing the machine instructions
• Linker: Combine all of the pieces into an executable
• Containing application code and library code

Important Points:

• These steps are performed "once"
• Executables are machine and OS specific

Tools:

• Editor: Create one or more source files
• Containing the program in human-readable form
• Interpreter: Execute the source file
• Each operation in the source file is "converted to" machine instructions each time it is encountered

Important Points:

• Editing is performed "once"
• Interpreting is performed every time the program is executed
• The interpreter is machine and OS specific

Tools:

• Editor: Create one or more source files
• Containing the program in human-readable form
• Compiler: Convert the source files to intermediate files (e.g., .class files)
• Containing byte codes that are similar to machine instructions but not specific to a machine/OS (hence are often said to be for a virtual machine)
• Interpreter: Execute the byte codes
• Convert the byte codes to machine instructions (either up-front or "just-in-time")

Important Points:

• Editing and compiling is done "once"
• The interpreter is used every execution
• The interpreter is machine and OS specific

• Editing:
  • You can use (almost) any editor
  • You can use an integrated development environment (IDE) like jGRASP, NetBeans, Eclipse, ...
• Compiling:
  • Command Shell: javac FileName.java
  • Eclipse: Compiles while you edit
• Executing:
  • Command Shell (or DrJava Interactions Pane): java FileName
  • Eclipse: Run-Run or

• What They Are:
  • Strings that are passed to an application (specifically, to the main() method in the main class) when it is executed
• Command Shell:
  • java FileName [arg]...
• Eclipse:
  • Run-Run configurations..., enter the project name and main class on the [Main] tab, and enter the arguments on the [Arguments] tab in the "Program arguments" section

• What Students Often Do:
  • Create a source file
  • Compile the source file
  • If there are compile-time (i.e., syntax) errors then curse
    Correct one or more errors (chosen randomly)
    Go to Step 2
  • Execute the program once without caring about the results
  • Use the electronic submission system
  • If there are run-time (e.g., logic) errors then curse
    Add a derogatory comment about the professor to the code
    Make a random change
    Go to Step 2
• Some Advice:
  • This is not a productive process (though it is fun to watch!)
  • Think before you act

• Be Judicious
  • Beginning students often mistakenly change code that is actually correct. They then become reluctant to change it back and this can lead to enormous amounts of wasted time.
• Use Comments
  • Don't delete code (initially), comment it out. This will help you remember what you've changed and make it easier to change it back if necessary.
• Think About What Needs To Be Re-Compiled
  • Not because it saves time (the compiler is very fast) but because it will help you understand the process better.

• Syntax Defects
• Use of an inappropriate lexical item
• Use of an inappropriate construct
• Missing punctuation
• Style Defects
• Failure to comply with the style guide
• Logic Defects
• Defects in the algorithm

• Compile-Time Errors:
  • Errors identified by the compiler/editor
  • Examples: Syntax errors
• Run-Time Errors:
  • Errors that occur during execution
  • Examples: Divide by zero, missing main, input mismatch
• Style Errors:
  • Aspects of the code that don't conform to the course style guide (which can be detected by inspection or using a tool)
  • Examples: Incorrect indentations, misplaced brackets

• Examples (in Java):
  • doubl result;
  • result = a $ b;
• Some Thoughts:
  • You should never make syntax errors but everyone makes occasional small mistakes
  • They will be "caught" by the compiler or a good editor

• A Necessary Skill:
  • Reading and understanding error messages
• A Necessary Discipline:
  • Always correct the first (top-most) error first!

• Computation Errors:
  • A formula's implementation is wrong
• Stress/Overload Errors:
  • A variable or data structure is filled past its capacity
• Throughput/Performance Errors:
  • The algorithm does not perform at the required "speed"

• A Necessary Skill:
  • Reading and understanding run-time error messages
• A Necessary Discipline:
  • Always correct the first (top-most) error first!