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And also, why is it not necessary for, eg: 

printf ("abc")
user2000809
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3 Answers3

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NSLog takes an NSString as argument. @"abc" denotes an NSString because of the @ sign, so that is a valid argument for NSLog. printf is a normal C function that takes a C string, which is simply created using "".

Scott Berrevoets
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    `@"abc"` is short for `[NSString stringWithString:@"abc"]` ?? This would be a recursive definition. – Martin R Feb 05 '13 at 19:22
  • @MartinR: You are correct! I believe it is `stringWithCString:encoding`, but feel free to correct me. – Scott Berrevoets Feb 05 '13 at 19:32
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    `@"abc"` creates a `NSString` object at compile time, it does not call `stringWithCString` or similar at runtime. – Martin R Feb 05 '13 at 19:34
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    @JamesBoutcher: I think `@"abc"` is called a *string literal*. Boxing is `@(c-string)`. – Martin R Feb 05 '13 at 19:41
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    `@"this is my string"` isn't _short_ for anything. It creates a literal `NSString` object that the compiler bakes right in to the binary. See, for example "[Does @"some text" give an autoreleased or retain 1 object back?](http://stackoverflow.com/q/6069459)". – jscs Feb 05 '13 at 20:18
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UPDATE:
 NSLog(@"%@",dictionary)

Tells the compiler that i got string to fulfill the requirement of string argument.

Update: Sorry I was supposed to write the "NSLog" instead of printf. my mistake!

Muhammad Noman
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    This does not work at all. Depending on your compiler settings, it will not compile, produce warnings, or give wrong results. `printf` does not accept an `NSString` as format string, and `printf` does not know the `%@` format. – Martin R Feb 06 '13 at 08:15
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Because it requires NSString. Adding @declares value as type of NSObject (simplification).

GregJaskiewicz
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