16 bit and 8-bit Representation

Two's Complement Representation - Quiz Explanation

The answers you selected are indicated below, along with text that explains the correct answers.
 
1. What range of integers can be represented using 16-bit two's complement representation?
Please select the best answer.
  A. -215 to 215 - 1
  B. -216 to 216 - 1
  C. -162 to 162
  The correct answer is A. Using two's complement representation with n bits you can represent the integers -2n-1 to 2n-1 - 1. Thus, with 16 bits you can represent the integers -215 to 215 - 1, or -32768 to 32767.

2. What is the decimal equivalent of the 8-bit two's complement number 10010111?
Please select the best answer.
  A. -104
  B. -152
  C. -105
  The correct answer is C. Reversing each bit of 10010111, we obtain 01101000. Adding 1 to 01101000 gives 01101001, which represents the decimal number 105. Thus, 10010111 represents the decimal number -105.

3. What is the 8-bit two's complement representation of the decimal number -18?
Please select the best answer.
  A. 11101101
  B. 00010010
  C. 11101101
  The correct answer is A. The 8-bit binary representation of the decimal number 18 is 00010010. Reversing each bit of 00010010, we obtain 11101101. Adding 1 to 11101101 gives 11101110. Thus, the 8-bit two's complement representation of the decimal number -18 is 11101110.