struct a collection of types, composite data type, composition, "user-definded data structure" struct Test { char* name; int nr; float f; };

Name of type is "struct Test", and not "Test" alone. struct Test myNewTest

Semicolon after closing parethesis is essentional.

Access composed types with dot-syntax: myNewTest.name = "hjkjnk"; myNewTest.nr = 32; myNewTest.f = 2.2424;

typedef a shorthand, an alias for a type, for ease of readability.

typedef int MyType

"MyType n;" would be equal to "int n;"

enum "introduces a symbolic name for an integer constant"

enum direction_enum {LEFT, RIGHT}; / LEFT -> 0, RIGHT -> 1; / enum direction_enum x = LEFT;

typedef enum typedef enum { LEFT; RIGHT; } direction; declatation: -(void)myFunction:(direction)LEFTorRIGHT;

call: -(void)myFunction:LEFT;

typedef struct

typedef struct objectInfo_ { CGPoint origin; NSString name; NSColor color; } objectInfo

Shortcut. Instead of writing 'struct objectInfo', write 'objectInfo'. The keyword 'objectInfo' seems to be optional.