"f" after number

When in doubt check the assembler output. For instance write a small, minimal snippet ie like this

#import <Cocoa/Cocoa.h>

void test() {
  CGRect r = CGRectMake(0.0f, 0.0f, 320.0f, 50.0f);
  NSLog(@"%f", r.size.width);
}

Then compile it to assembler with the -S option.

gcc -S test.m

Save the assembler output in the test.s file and remove .0f from the constants and repeat the compile command. Then do a diff of the new test.s and previous one. Think that should show if there are any real differences. I think too many have a vision of what they think the compiler does, but at the end of the day one should know how to verify any theories.

CGRect frame = CGRectMake(0.0f, 0.0f, 320.0f, 50.0f);

uses float constants. (The constant 0.0 usually declares a double in Objective-C; putting an f on the end - 0.0f - declares the constant as a (32-bit) float.)

CGRect frame = CGRectMake(0, 0, 320, 50);

uses ints which will be automatically converted to floats.

In this case, there's no (practical) difference between the two.