What is Floating-Point Operations
Floating-point values do not follow the rules of integer division—that is, dividing by floating-point values produces floating-point results.
In certain programming languages (Java comes to mind) the float type is almost never used. In Objective-C, it is the more commonly used of the two—both for practical and memory reasons.
A floating point number must contain a decimal portion, but you can omit digits before or after the decimal point—obviously, not both. The entire number ca be prefixed by a negative sign. Therefore, 3., 1.8, .295, and -.59 are all valid floating point numbers. To display floats in an NSLog call, use %f.
As you may recall from a high-school math class, scientific notation is a method of writing absurdly large or small numbers. It takes the form 5.925×102, where the general notation is of a floating-point value followed by a multiplication, a number (generally a power of 10), and an exponent. This number is written in code with the form 5.925e4. The e, formally known as the mantissa, can be written as a capital or lowercase. The mantissa can be either positive or negative; a negative value, such as 2.25e-3, would correspond to a value of 2.25×10-3, or 0.00225.
To display scientific notation, use %e. Alternatively, you can use %g to have NSLog decide whether to display the usual value or the scientific notation—if the exponent is less than -4 or greater than 5, the scientific notation is used; otherwise, the standard floating point notation is used.
A double value is a more precise float value—the former stores twice as many digits, and on most systems it uses 64 bits.
Like Java, all floating point constants in Objective-C are double. To force a float, append either f or F to the end of the floating point value. Unlike Java, however, floats are used as a general data type for floating-point variables, due to the fact that they require less memory. The distinction is that of constants versus that of variables.