- #define - A keyword that is used to define a macro, variable, etc. for the C preprocessor.
- #include - A keyword that is used to inform the C preprocessor to open another file and process that.
- #if - A keyword that is used to inform the C preprocessor to only include the encapsulated code in the program if a given criteria is met.
- #else - A keyword that is used in conjunction with #if that informs the C preprocessor to include the encapsulated code in the program if the criteria is not matched by the corresponding #if statement.
- #elif - A keyword that is used in conjunction with #if that informs the C preprocessor to include the encapsulated code in the program if the criteria is not matched by the corresponding #if statement and it matches the supplied logical statement.
- #endif - A keyword that is used to inform the C preprocessor to end the last #if statement
C comments are statements not interpreted by the compiler and are used by the programmer to leave helpful notes on what is happening in the code. Comments are contained within the /* and */ symbols.
A C keyword used to express a non-fractional number that is commonly called an integer.
C keywords are words recognized by the compiler to denote certain operations. A full list of standard keywords includes:
auto break case char const continue default do double else enum extern float for goto if int long register return short signed sizeof static struct switch typedef union unsigned void volatile while
In addition, GCC allows the use of in-line assembler by using the
Standard C language modifiers include:
auto extern register static typedef volatile
Operators are symbols that when used, perform an operation on one or more operands. C uses the following operators:
, Used to separate expressions foo, bar = Assignment foo = bar ? : Conditional foo?bar:baz || Logical OR foo || bar && Logical AND foo && bar | Bitwise OR foo | bar ^ Bitwise Exclusive-OR (XOR) foo ^ bar & Bitwise AND foo & bar == Equality foo == bar != Inequality foo != bar <= Less than or Equals foo <= bar >= Greater than or Equals foo >= bar < Less than foo < bar > Greater than foo > bar << Left shift foo << bar >> Right shift foo >> bar + Addition or no-op foo + bar or +foo - Subtraction or negation foo - bar or -foo * Multiplication or de-assignment foo * bar or *foo / Division foo/bar % Modulus foo%bar ~ Bitwise compliment ~foo ! Logical compliment !foo ++ pre- or post- decrement ++foo or foo++ -- pre- or post- decrement --foo or foo-- () Type casting or precedence (int) foo or (char) foo, etc or (2 + 3) * 8, etc -> Structure de-referencing foo -> bar . Structure reference foo.bar  Array reference foo[bar]