Beginner programming question

I have finally gotten my Arduino Uno and after playing with the blink and fade routines a little bit to test if everything is working alright I noticed that there seems to be a bunch of stuff missing in the code. Only the void setup() and void loop() portions. Some of the other sketches have some definitions before the setup() or additional functions to be called from the loop() but when I was looking at some other examples in C they usually have stuff like #include <stdint.h> #include <stdlib.h> #include <inttypes.h> or such at the top. Is the Arduino IDE automatically adding stuff to the “programming” I write and if so what is it adding? If I have a programfile.c written by someone else (open source so no copywrite issues) do I have to do some editing of the programfile.c to make a programfile.pde usable by Arduino IDE to get it on my atmega MCU?

If I understand your questions correctly there are two answers.

  1. Some Arduino sketches don’t need to have code in the loop (code in setup() will only run as soon as the Arduino is powered) or the setup() (but not both, then the Arduino wouldn’t do anything really).

  2. A definition, like in other programming languages, is you telling the program to include new libraries of code and cool wonderful functions to your program. So when you say #include <LiquidCrystal.h> you’re telling the program to include the lcd libraries which aren’t normally included.

As for the C coding issues, from what I know it should work if you copy paste, but if it doesn’t the compiler should be able to tell you if something isn’t right. Granted… I don’t know how to code in C so take that for what you will.

Is the Arduino IDE automatically adding stuff to the “programming” I write and if so what is it adding?

A C program has to have a “main”, so the IDE adds one.
It also adds a call to an invisible function “init” which sets up the state of the timers and so on, so your sketch looks more like this:

#include <WProgram.h>

int main(void)
{
	init();

	setup();
    
	for (;;)
		loop();
        
	return 0;
}

You can look at the code in “init()” in a source file called “wiring.c” in your distribution.

You can look at the code in "init()" in a source file called "wiring.c" in your distribution

I looked in several of the directories installed when I installed Arduino IDE but didn't find any file called "wiring.c" Found "wiring.cpp" and "wire.h" which begs me to ask this question:
What are the different file extensions and what do they contain? I have seen the following online referenced and don't know where they come from or whether I can copy/paste the examples into code of my own:
.elf
.c
.cpp
.h
.pde

Clearing this part up will help me a lot.
Dmac257

wiring.c is in hardware/arduino/cores/arduino.

As to the others:
.elf Executable and Linkable Format - Wikipedia
.pde http://filext.com/file-extension/PDE It's the sketch that gets processed as AWOL describes
.c: C Source code file
.cpp: C++ Source code file
.h C or C++ header file