macOS what is the '#pragma '' usage?

#import "MyController.h"

@implementation MyController



#pragma mark -
#pragma mark Startup and Shutdown

- (id) init
{
if (self = [super init])
{
_mailboxes = [[NSMutableArray alloc] init];
}
return self;
}

- (void) dealloc
{
[_mailboxes release];

[super dealloc];
}



#pragma mark -
#pragma mark Simple Accessors

- (NSMutableArray *) mailboxes
{
return _mailboxes;
}

- (void) setMailboxes: (NSArray *)newMailboxes
{
if (_mailboxes != newMailboxes)
{
[_mailboxes autorelease];
_mailboxes = [[NSMutableArray alloc] initWithArray: newMailboxes];
}
}


@end
------------------------------------------------------------------------------------------
As the above sample code shown, what do the #pragma sentences mean?
I have read the Programming in Objective-C, but it doesn't make me understood yet. Could someone explain more clearly? Thank you!

Paragraph in Programming in Objective-C:

The #pragma Directive
General Format:



#pragma text

This causes the preprocessor to perform some implementation-defined action. For example, under the pragma



#pragma loop_opt(on)

causes special loop optimization to be performed on a particular compiler. If this pragma is encountered by a compiler that doesn't recognize the loop_opt pragma, it is ignored.

The special keyword STDC is used after the #pragma for special meaning. Current supported switches that can follow a #pragma STDC are FP_CONTRACT, FENV_ACCESS, and CX_LIMITED_RANGE.

robbieduncan said:

#pragma mark directives show up in XCode in the menus for direct access to methods. They have no impact on the program at all.

Click to expand...

It means that these sentences are used as 'comment'?

what's the difference between '#pragma mark' and usual comment?
Why does the author write so?

robbieduncan said:

There are lots. They are compiler (or pre-processor) specific pragmatic information.

You can get info on the GCC ones here

Unrecognised pragmas like mark will be ignored by the compiler so can safely be used for other purposes, such as layout hints for IDEs

Click to expand...

Thank you! Friend! It sounds wonderful of the usage of '#pragma mark'. I'll try when my Mac machine arrives.

BTW:where can I get more "#pragma" info for XCode?