Preprocessor Directives

1. Definition: commands handed off to the C preprocessor (which modifies the code before it is compiled)
2. #include is used to add libraries of functions to a C program

   Example: #include <stdio.h>

   
   
3. #define creates a constant whose value may not be changed

   Example: #define PI 3.14159

   
   

The main() Function

1. main() is the entry point for execution for all C programs
2. In ANSI C, main() is an int, meaning it returns an integer to the operating system (usually 0)

   Example: int main() { ... code goes here ... ... code goes here ... return 0; }

   
   

Variables

1. Declared either before main() (global) or inside a function (local)
2. Some valid variable types:

   char	used for characters
   short	-32,768 to 32,767
   unsigned short	0 to 65535
   long	-2,147,483,648 to 2,147,483,647
   int (16-bit)	-32,768 to 32,767
   int (32-bit)	-2,147,483,648 to 2,147,483,647
   float
   double

3. Multiple variables can be assigned with one type declaration
4. A variable can be assigned a value at the time of declaration

   Example: int MyAge; double cost, distance = 4.3;

   
   

Comments

1. C style: /* Comments in here */
2. C++ style: // Comments until the end of the line

   Example: int MyAge; // This is the my age variable double cost, distance = 4.3; /* Create a variable of type double for cost and distance, setting distance equal to 4.3 */

   
   

Other

1. Lines end with a semicolon
2. Capitalization does matter!
3. C source code files usually end in ".c"