Purpose of using union within structure in c -

typedef struct {   int k;   union   {     int i;     int j;   }use;  }std; 

directly can use variable , j in structure why used within union.

in example, i.e.

typedef struct {   int k;   union   {     int i;     int j;   }use;  }std; 

it doesn't seem make sense i , j same type , names of variables isn't descriptive.

it can make sense have same type union elements if make code easier write, read, understand , maintain. example:

... union {       int numberofcars;     int numberofbicycles; }use; ... 

when writing code handling cars use numberofcars , when writing code handling bicycles use numberofbicycles. in way code easier understand/maintain , 2 code blocks still share common structure.

in 1 code block have:

std cardealer; cardealer.use.numberofcars = 9; 

and in code block (other file perhaps), have:

std bicyclesdealer; bicyclesdealer.use.numberofbicycles = 9; 

a more typical case unions elements of different type.