Floating point numbers follow the IEEE 754 standard and represent numbers with a decimal point, such as 3.14, or an exponent notation, such as 4e-14, and come in the types Float16 up to Float64, the last one being used for double precision.
Single precision is achieved through the use of the Float32 type. Single precision float literals must be written in scientific notation, such as 3.14f0, but with f, where one normally uses e. That is, 2.5f2 indicates 2.5*10^2 with single precision, while 2.5e2 indicates 2.5*10^2 in double precision. Julia also has a BigFloat type for arbitrary-precision floating numbers computations.
A built-in type promotion system takes care of all the numeric types that can work together seamlessly, so that there is no explicit conversion needed. Special values exist: Inf and -Inf are used for infinity, and NaN...