Answer Posted / ravi

structure is collection of different data types.
union is same as the structures, the only difference is in
memory allocation.
struct
{
int a;
float b;
};
struct s;
s.a=10;
s.b=3.0;
printf("%d%f",s.a,s.b);

For the above structure it allocates 2bytes for integer
variable and 4 bytes for flaot variable. so totally it
allocates 6bytes of memory to that structure. we can print
the s.a and s.b values as 10 and 3.0
#include<stdio.h>
union
{
int a;
char ch;
}u;

u.a=100;
u.ch='a';
printf("%d\n%d",u.a,u.ch);


But incase of union, the memory allocated is maximum
memory required among the variables. so only 4 bytes is
allocated to unions.
if u try to print the u.a, u.ch values it prints 97, 97
where the value of u.a is being assigned by u.ch . so we
cannt get value of u.a at last. It wont happen incase of
structures. so mostly we use structures in programming.

A banker has a seif with a cipher. Not to forget the cipher, he wants to write it coded as following: each digit to be replaced with the difference of 9 with the current digit. The banker chose a cipher. Decipher it knowing the cipher starts with a digit different than 9. I need to write a program that takes the cipher from the keyboard and prints the new cipher. I thought of the following: Take the input from the keyboard and put it into a string or an array. Go through the object with a for and for each digit other than the first, substract it from 9 and add it to another variable. Print the new variable. Theoretically I thought of it but I don't know much C. Could you give me any kind of hint, whether I am on the right track or not?

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