If the variables in a union use the same address so the previous value will be lost if a new value is entered how do you get the previous value?

Answer 1

Answer

quite a low level view required ......everything stored in memmory is in form of bits (i.e. a sequence of 01). It dependes upon how you are going to read a value. Same sequence of bits can give you different values..try printing x=10; printf("%c %d",x,x);

AnswerThis is the same problem as getting the previous value of a regular variable. For example:
int x = 5;
x = 2;

How do you get the previous value of x (5)? If you didn't store the value in another variable before overwriting it with 2, then you can't. The old value is overwritten and cannot be recovered. In a union, it's possible that you might overwrite only part of a previous value if you store a value to a smaller data type. For example:
union { long a; short b; } c;
c.a = 5;
c.b = 2;

It's possible that you can recover some of the old data of c.a, but for most practical purposes that value would be garbage (and it really depends on the exact alignment of the variables and byte endianness).