Question

Problem Statement: The "Gottcha Anti-Theft" Machine There are many anti-theft devices on the market that attempt to foil a would-be robber from starting your car and driving off with it. One popular item has a keypad like a touch-tone telephone. In order to start your car, you must key in a secret four digit decimal code, such as '3719'. It only "remembers" the most recent four digits you have keyed in. Thus the sequence '3723719' will let you start your car. For simplicity here we use a code based on a sequence of eight binary bits, and use two push buttons to enter a sequence serially. Each press of a button enters the corresponding digit. finger secret byte 01100111 0 1 enable for the starter motor E Figure 1. The Gottcha machine in action. As you key in the bits in sequence, the device outputs $E = 0$ until the most recent eight bits agree with a built-in secret code byte. Then $E$ switches to 1.

          Problem Statement: The "Gottcha Anti-Theft" Machine
There are many anti-theft devices on the market that attempt to foil a would-be robber from
starting your car and driving off with it. One popular item has a keypad like a touch-tone
telephone. In order to start your car, you must key in a secret four digit decimal code, such
as '3719'. It only "remembers" the most recent four digits you have keyed in. Thus the
sequence '3723719' will let you start your car.
For simplicity here we use a code based on a sequence of eight binary bits, and use two
push buttons to enter a sequence serially. Each press of a button enters the corresponding
digit.
finger
secret byte
01100111
0
1
enable for the
starter motor
E
Figure 1. The Gottcha machine in action.
As you key in the bits in sequence, the device outputs $E = 0$ until the most recent eight bits
agree with a built-in secret code byte. Then $E$ switches to 1.

Problem Statement: The "Gottcha Anti-Theft" Machine
There are many anti-theft devices on the market that attempt to foil a would-be robber from
starting your car and driving off with it. One popular item has a keypad like a touch-tone
telephone. In order to start your car, you must key in a secret four digit decimal code, such
as '3719'. It only "remembers" the most recent four digits you have keyed in. Thus the
sequence '3723719' will let you start your car.
For simplicity here we use a code based on a sequence of eight binary bits, and use two
push buttons to enter a sequence serially. Each press of a button enters the corresponding
digit.
finger
secret byte
01100111
0
1
enable for the
starter motor
E
Figure 1. The Gottcha machine in action.
As you key in the bits in sequence, the device outputs E = 0 until the most recent eight bits
agree with a built-in secret code byte. Then E switches to 1.

Added by David S.

Question

Please give Ace some feedback