What is the function of sucrase in the breakdown of table sugar\

A starch molecule is formed when many disaccharide molecules are combined.  Starch is often produced in plants as a means of storing energy. The two other molecules formed when multiple disaccharide molecules are combined are cellulose and glycogen. The cell walls in plants are made up of cellulose. Glycogen is a carbohydrate energy source. 
A disaccharide molecule is formed when two monosaccharide molecules are joined together. Maltose, sucrose and lactose are the most important disaccharides. A monosaccharide molecule is a simple sugar, for example, glucose. 

Are you asking about a street map usage  if so here is your answer  a street map for a very limited area could simply be a bit map or a .jpg image.  but a more general map would probably store the streets as vectors.  but you shouldn't assume that there is one way to do it