Judging and coding of D,L configuration of open chain form structure,D,L configuration of straight chain form and Haworth formular of oxido-cyclic form structure of monosaccharide which is the basic unit of sugar are explained.

• 糖类结构的基本单元是单糖；介绍了单糖开链结构的D；L构型、氧环式结构的直链型D；L构型、氧环式结构的哈武斯式D；L构型的判断和标记方法.