A structure is a collection of variables under a single name. These variables can be of different types, and each has a name which is used to select it from the structure. A structure is a convenient way of grouping several pieces of related information together.
Structure has name mystruct and it contains two variables: an integer named numb and a character named ch.
Declaring structure variable
struct mystruct s1;
Accessing Member Variables
typedef can also be used with structures. The following creates a new type sb which is of type struct chk and can be initialised as usual:
typedef struct chk
Unions in C
A union is an object that can hold any one of a set of named members. The members of the named set can be of any data type. Members are overlaid in storage. The storage allocated for a union is the storage required for the largest member of the union, plus any padding required for the union to end at a natural boundary of its strictest member.