Question 17

1)X-Y binary-coded decimal, also called biased representation, is a numeral system used on some older computers that uses a pre-specified number N as a biasing value. It is a way to represent values with a balanced number of positive and negative numbers. In X, numbers are represented as decimal digits, and each digit is represented by four bits as the BCD value plus Y (the "X" amount):The smallest binary number represents the smallest value. (i.e. 0 − X Value) The greatest binary number represents the largest value. (i.e. 2 N+1 − X Value − 1) The primary advantage of this coding over BCD coding is that a decimal number can be nines' complemented (for subtraction) as easily as a binary number can be ones' complemented; just invert all bits. In addition, when the sum of two digits is greater than 9, the carry bit of a four bit adder will be set high. This works because, when adding two numbers that are greater or equal to zero, an "X" value of six results in the sum. Since a four bit integer can only hold values 0 to 15, an X of six means that any sum over nine will overflow. Adding X-Y works on a different algorithm than BCD coding or regular binary numbers. When you add two numbers in this system together, the result is not an X-Y number. In order to correct this problem, when you are finished adding each digit, you have to subtract Y if the digit is less than decimal 10 and add Y if the number is greater than or equal to decimal 10 (thus causing the number to wrap).

2)An Z cipher, also known as Z's cipher, the shift cipher, Z's code or Z shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example,with a shift of Y. The method is named after Z, who used it to communicate with his generals.The encryption step performed by a Z cipher is often incorporated as part of more complex schemes, such as the Vigenère cipher, and still has modern application in the ROT13 system. As with all single alphabet substitution ciphers, Z cipher is easily broken and in practice offers essentially no communication security.

As is evident from the text,

1 is a numeral system.

2 is an encryption technique.

Both use the same funda.Plenty of clues in question.

Identify X,Y,Z.

Answer:The Excess-3(XS-3)numeral system and the Caesar cipher, named after Julius Caesar.