42. (a) 56 6P 89 C3 A0(U) 4B03 A473 65 (c) 70 C3 A2 74 65 42. You are the chief

Question

42.

(a) 56 6P 89 C3 A0(U) 4B03 A473 65 (c) 70 C3 A2 74 65 42. You are the chief communications officer for the Lower Slobovian army at war with the Upper Slobovians. Your spies will infiltrate the enemy's command headquarters in an attempt to gain the "upper" hand. You know the Uppers are planning a major assault, and you also know the following: (1) It will be at either sunrise or sunset, (2) it will come by land, air, or sea, and (3) it will occur on March 28, 29, 30, or 31, or on April 1. Your spies must communicate with you in binary. Devise a suitable binary code for transmitting the information. Try to use the fewest number of bits possible. 43. Octal numbers are sometimes used instead of hexadecimal numbers to represent bit sequences. ta) How many bits does one octal number represent?

Explanation / Answer

42.

We know that the following things:

a. It will occur at either sunrise or sunset.

b. It will come by land, air, or sea.

c.It will occur on March 28,29,30 or 31 or on April 1.

The answer is using 6 bits of binary code.

The first bit indicates if its sunrise or sunset.

0 - sunrise

1 - sunset

The next 2 bits indicate whether the attack will come from land, air or sea.

00 - land

01 - air

10 - sea

The next bit indicates which month

0 - March

1 - April

The next 2 bits indicate the date

(Since we know if it is either on the first of April or other days, if the bit preceding the last two bits is 1 then the only date possible is April 1 so the last two bits will be 0 in this case)

00 - The first date of the month (Can be 28 or 1) depending on the bit before that.

01 - 29

10 - 30

11 - 31

Example:

010001 - Sunrise by sea on March 29th

101100 - Sunset by air on April 1

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