Having the prototype available before the first use of the function allows the compiler to check that the correct number and type of arguments are used in the function call and that the returned value, if any, is being used reasonably. The function definition itself can act as an implicit function declaration.
While shellac is not usually the finish paint choice, it is often thought of as the best paint primer available. It has properties that oil and water based paints can't match, and provides a more dependable seal than most other primers are able to provide.
via CND and SNS. I first starting using Shellac back in 2012 when I bought my own equipment and did it myself from home. My favourite brands were CND and Red Carpet. Shellac is basically a mixture of gel and nail polish.