Edit code for all snippets to compile properly. Re-word some descriptions.

objective-c.html.markdown

@@ -76,16 +76,16 @@ int main (int argc, const char * argv[])
     short fortyTwoShort           = [fortyTwoShortNumber shortValue]; // or 42
     NSLog(@"%hi", fortyTwoShort);
 
-    NSNumber *fortyTwoShortNumber   = [NSNumber numberWithShort:41];
+    NSNumber *fortyOneShortNumber   = [NSNumber numberWithShort:41];
-    unsigned short fortyTwoUnsigned = [fortyTwoShortNumber unsignedShortValue]; // or 41
+    unsigned short fortyOneUnsigned = [fortyOneShortNumber unsignedShortValue]; // or 41
-    NSLog(@"%hu", fortyTwoUnsigned);
+    NSLog(@"%u", fortyOneUnsigned);
     
     NSNumber *fortyTwoLongNumber = @42L;
     long fortyTwoLong            = [fortyTwoLongNumber longValue]; // or 42
     NSLog(@"%li", fortyTwoLong);
 
-    NSNumber *fortyTwoLongNumber     = @53L;
+    NSNumber *fiftyThreeLongNumber   = @53L;
-    unsigned long fiftyThreeUnsigned = [fortyTwoLongNumber unsignedLongValue]; // or 53
+    unsigned long fiftyThreeUnsigned = [fiftyThreeLongNumber unsignedLongValue]; // or 53
     NSLog(@"%lu", fiftyThreeUnsigned);
 
     // Floating point literals
@@ -118,6 +118,7 @@ int main (int argc, const char * argv[])
     NSLog(@"%i", yesBool); // prints => 1
 
     // Array object
+    // May contain different data types, but must be an Objective-C object.
     NSArray *anArray      = @[@1, @2, @3, @4];
     NSNumber *thirdNumber = anArray[2];
     NSLog(@"Third number = %@", thirdNumber); // Print "Third number = 3"
@@ -148,10 +149,6 @@ int main (int argc, const char * argv[])
     [mutableSet addObject:@"Hello"];
     NSLog(@"%@", mutableSet); // prints => {(Hello)}
 
-    // Set object
-    NSSet *set = [NSSet setWithObjects:@"Hello", @"Hello", @"World", nil];
-    NSLog(@"%@", set); // prints => {(Hello, World)}
-
     ///////////////////////////////////////
     // Operators
     ///////////////////////////////////////
@@ -299,9 +296,9 @@ int main (int argc, const char * argv[])
 }
 // Convenient notation for public access variables to auto generate a setter method. 
 // By default, setter method name is 'set' followed by @property variable name.
-@property int count; // Setter name = 'setCount'
+@property int count; // Setter method name = 'setCount'
 @property (copy) NSString *name; // (copy) => Copy the object during assignment.
-@property (readonly) id data;    // (readonly) => Declare only a getter method.
+@property (readonly) id data;    // (readonly) => Cannot set value outside interface.
 // You can customize the getter and setter names instead of using default 'set' name:
 @property (getter=lengthGet, setter=lengthSet:) int length;
  
@@ -322,7 +319,7 @@ int main (int argc, const char * argv[])
 // automatically. Method name is 'set' followed by @property variable name:
 MyClass *myClass = [[MyClass alloc] init]; // create MyClass object instance.
 [myClass setCount:10]; 
-NSLog(@"%@", [myClass count]); // prints => 10
+NSLog(@"%d", [myClass count]); // prints => 10
 // Or using the custom getter and setter method defined in @interface:
 [myClass lengthSet:32];
 NSLog(@"%i", [myClass lengthGet]); // prints => 32
@@ -349,7 +346,7 @@ NSLog(@"%li", distance); // prints => 18
 }
 
 // Constructors are a way of creating classes
-// This is a default constructor which is called when the object is creating
+// This is a default constructor which is called when the object is initialized. 
 - (id)init
 {
     if ((self = [super init]))
@@ -410,31 +407,34 @@ With all object interactions, follow the pattern of:
 (1) create the object, (2) use the object, (3) then free the object from memory. 
 */
 
-MyClass *classVar = [MyClass alloc]; // alloc sets classVar's reference count to one. Returns pointer to object.
+MyClass *classVar = [MyClass alloc]; // 'alloc' sets classVar's reference count to one. Returns pointer to object.
 [classVar release]; // Decrements classVar's reference count.  
-// retain claims ownership of existing object instance and increments reference count. Returns pointer to object.
+// 'retain' claims ownership of existing object instance and increments reference count. Returns pointer to object.
 MyClass *newVar = [classVar retain]; // If classVar is released, object is still in memory because newVar is owner.
 [classVar autorelease]; // Removes ownership of object at end of @autoreleasepool block. Returns pointer to object.
 
-// @property can use retain or assign as well for small convenient definitions. 
+// @property can use 'retain' and 'assign' as well for small convenient definitions. 
 @property (retain) MyClass *instance; // Release old value and retain a new one (strong reference).
 @property (assign) NSSet *set; // Pointer to new value without retaining/releasing old (weak reference).
 
+// Automatic Reference Counting (ARC)
 // Because memory management can be a pain, Xcode 4.2 and iOS 4 introduced Automatic Reference Counting (ARC).
 // ARC is a compiler feature that inserts retain, release, and autorelease automatically for you, so when using ARC, 
 // you must not use retain, relase, or autorelease.
-MyClass *arcMyClass = [[MyClass alloc] init]; // Without ARC, you will need to call: [arcMyClass release] after
+MyClass *arcMyClass = [[MyClass alloc] init]; 
-// you're done using arcMyClass. But with ARC, there is no need. It will insert this release statement for you. 
+// ... code using arcMyClass
+// Without ARC, you will need to call: [arcMyClass release] after you're done using arcMyClass. But with ARC, 
+// there is no need. It will insert this release statement for you. 
 
-// As for the "assign" and "retain" @property attributes, with ARC you use "weak" and "strong". 
+// As for the 'assign' and 'retain' @property attributes, with ARC you use 'weak' and 'strong'. 
-@property (weak) MyClass *weakVar; // weak does not take ownership of object. If original instance's reference count
+@property (weak) MyClass *weakVar; // 'weak' does not take ownership of object. If original instance's reference count
 // is set to zero, weakVar will automatically receive value of nil to avoid application crashing.
-@property (strong) MyClass *strongVar; // strong takes ownership of object. Ensures object will stay in memory to use.
+@property (strong) MyClass *strongVar; // 'strong' takes ownership of object. Ensures object will stay in memory to use.
 
 // For regular variables (not @property declared variables), use the following:
 __strong NSString *strongString; // Default. Variable is retained in memory until it leaves it's scope. 
 __weak NSSet *weakSet; // Weak reference to existing object. When existing object is released, weakSet is set to nil.
-__unsafe_unretained NSArray *unsafeArray; // Like __weak but unsafeArray not set to nil when existing object is released.
+__unsafe_unretained NSArray *unsafeArray; // Like __weak, but unsafeArray not set to nil when existing object is released.
 
 ```
 ## Further Reading