what does the .f in 1000.f mean? c++ [duplicate]

This question already has answers here: Purpose of a ".f" appended to a number? (5 answers) 开发者_Python百科 Closed 5 years ago.

I am following a tutorial on how to make a game with SDL. At a certain point in the tutorial I need to calculate the game's FPS. The tutorial does the following:

caption << "Average Frames Per Second: " << frame / ( fps.get_ticks() / 1000.f );

Now, I know exactly what the code does, except for the part where it divides by 1000.f. I've been looking but just can't find what .f means.

So my question is, what does .f mean? And why is it there?

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1000 is an int literal.

1000. is a double literal.

1000.f is a float literal.

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It means this is a float constant rather than a double constant. As for the effect, on most C++ compilers, it will have no effect as the float will be converted to a double to do the divide.

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.f makes the number float type.

Just see this interesting demonstration:

float a = 3.2;
if ( a == 3.2 )
    cout << "a is equal to 3.2"<<endl;
else
    cout << "a is not equal to 3.2"<<endl;

float b = 3.2f;
if ( b == 3.2f )
    cout << "b is equal to 3.2f"<<endl;
else
    cout << "b is not equal to 3.2f"<<endl;

Output:

a is not equal to 3.2
b is equal to 3.2f

Do experiment here at ideone: http://www.ideone.com/WS1az

Try changing the type of the variable a from float to double, see the result again!

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It is telling you the literal 1000. should be treated as a float. Look here for details.

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It means 1000.f is treated as a float.

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A floating point literal can have a suffix of (f, F, l or L). "f and F" specify a float constant and "l and L" a double.