Maltose is a common disaccharide that is formed by the dehydration reaction of two glucose molecules. The glycosidic bond present in maltose is $\mathrm{\alpha }-1,4$. During the formation, from two glucose molecules, one molecule of water is removed.

Thus, the formula of maltose becomes ${\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}$