Inside an IDE

An Integrated Development Environment (IDE) puts the tools a programmer needs into one program: an editor, a translator (compiler or interpreter), a debugger and often a file/project manager.

"Integrated" is the point: you write, translate and debug without switching applications.

• Context-sensitive prompts: as you type, the IDE suggests the names, methods and parameters that make sense where you are — for example, offering the methods of the object you just typed a dot after.
• Syntax highlighting: keywords, strings and comments are coloured so the structure is easier to scan.
• Auto-indent and auto-complete: the editor lines up code blocks and finishes words for you.

Context-sensitive means the suggestion depends on context. A prompt offering every variable in the program would not be context-sensitive.

• Dynamic syntax checks: the editor checks the code while you type and underlines mistakes immediately, before you even translate.
• Error markers and messages: a marker in the margin and a message explaining the problem.

This catches errors early, which is cheaper than finding them at run time — but it cannot catch logic errors, because the code is still syntactically valid.

• Prettyprint: automatically formats the code (indentation, spacing, line breaks) so it is readable.
• Expanding and collapsing code blocks: fold a long procedure to a single line so you can see the structure of a big program.
• Line numbers and bookmarks: help you navigate.

None of these change what the program does — they change how easy it is to read.

• Breakpoints: mark a line where execution should pause, so you can inspect the state at that point.
• Single stepping: run one line at a time (step into a procedure, or step over it).
• Watching variables and expressions: display their current values and update them as you step.
• Report window: shows output, errors, and the values being watched while the program runs.

A breakpoint plus a watched variable is the standard way to answer "why is this value wrong here?".