An example of union in C

1. Definition:

union(int i, short s, char c) un;
un.i = 3;
printf( " i=%d " ,un.i);
printf( " length = %d\n " ,sizeof(un);//==4 , has the largest variable to determine

2. Equivalent to List T in java

3. Data exchange

void swap(int *p , int *q){
int temp = *p;
*p = *q;
*q = temp;
}

4. Print the address

int i = 2;
printf( " %#x " ,&i);

5. Pointer prints array values

int arr[] = {1,2,3,4};
int *p = &arr;
prinft( " %d\n " , *(p+0));
prinft( " %d\n " , *(p+1));

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