ARRAYS - Java Programming: From Problem Analysis to Program Design - page 605

PROGRAMMING EXAMPLE: Code Detection
When a message is transmitted in secret code over a transmission channel, it is
usually transmitted as a sequence of bits, that is, 0s and 1s. Due to noise in the
transmission channel, the transmitted message may become corrupted. That is, the
message received at the destination is not the same as the message transmitted;
some of the bits may have been changed. There are several techniques to check
the validity of the transmitted message at the destination. One technique is to
transmit the same message twice. At the destination, both copies of the message are
compared bit-by-bit. If the corresponding bits are the same, the message is assumed
to have been received error-free.
Let's write a program to check whether the message received at the destination is
likely error-free. For simplicity, assume that the secret code representing the message
is a sequence of digits (0 to 9). Also, the first number in the message is the length of
the message. For example, if the secret code is:
7 9 2 7 8 3 5 6
then the actual message is 7 digits long, and it is transmitted twice.
The above message is transmitted as:

7 9 2 7 8 3 5 6 7 9 2 7 8 3 5 6

The secret code and its copy. Input:

9

Output: The secret code, its copy, and a message—if the received code is error-free—in
the following form:
Code Digit Code Digit Copy
9 9
2 2
7 7
8 8
3 3
5 5
6 6
Message transmitted OK.
The preceding output is to be stored in a file.

Because we have to compare the corresponding digits of the secret code and its copy,
you first read the secret code and store it in an array. Then you read the first digit of
the copy and compare it with the first digit of the secret code, and so on. If any
corresponding digits are not the same, you indicate this fact by printing a message
next to the digits. We use an array to store the secret code. The first number in the
secret code, and in the copy of the secret code, indicates the length of the code. This
discussion translates into the following algorithm:

PROBLEM
ANALYSIS
AND
ALGORITHM
DESIGN