Example of union Declaration and Use

The following example defines a union data type (not named) and a union variable (named length). The member of length can be a long int, a float, or a double.

union {
        float meters;
        double centimeters;
        long inches;
      } length;

The following example defines the union type data as containing one member. The member can be named charctr, whole, or real. The second statement defines two data type variables: input and output.

union data {
             char charctr;
             int whole;
             float real;
           };
union data input, output;

The following statement assigns a character to input:

input.charctr = 'h';

The following statement assigns a floating-point number to member output:

output.real = 9.2;

The following example defines an array of structures named records. Each element of records contains three members: the integer id_num, the integer type_of_input, and the union variable input, which has the union data type defined in the previous example.

struct {
         int id_num;
         int type_of_input;
         union data input;
       } records[10];

The following statement assigns a character to the structure member input of the first element of records:

records[0].input.charctr = 'g';

union (Unions) Type