CS101 Mock: Signed Number Representations
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Questions and Answers

What does the leftmost bit represent in sign/magnitude notation?

  • The total number of bits used
  • The magnitude of the number
  • The sign of the number (correct)
  • The representation of zero
  • How many unique patterns can be represented with m binary digits?

  • m
  • 0
  • $m^2$
  • $2^m$ (correct)
  • What is a potential complication of using sign/magnitude representation?

  • It loses accuracy in calculations.
  • It has two representations for zero. (correct)
  • It requires more bits than unsigned numbers.
  • It cannot represent negative numbers.
  • What technique divides the available patterns into positive and negative portions?

    <p>Sign/magnitude</p> Signup and view all the answers

    What might be required to compare two sign/magnitude numbers for equality?

    <p>An extra check for zero</p> Signup and view all the answers

    In the context of radix complementation, what point does an integer A being positive imply about its sign bit?

    <p>It is 0.</p> Signup and view all the answers

    Which representation allows for two distinct values for zero?

    <p>Sign/magnitude notation</p> Signup and view all the answers

    What is true about the number of patterns used in signed representations as compared to unsigned representations?

    <p>Both use the same number of patterns.</p> Signup and view all the answers

    What is the largest positive number that can be represented using four bits in sign magnitude representation?

    <p>+7</p> Signup and view all the answers

    Using four bits, which two's complement representation corresponds to the decimal value -1?

    <p>1111</p> Signup and view all the answers

    What pattern emerges when all four bits in the two's complement representation are set to 1?

    <p>-1</p> Signup and view all the answers

    When representing negative integers using two's complement, why can one additional negative integer be represented compared to positive integers?

    <p>Because 0 is represented in positive integers</p> Signup and view all the answers

    What is the formula used to derive the value of a negative integer in two's complement?

    <p>Val = -2^(n-1) + Σ2^i A_i</p> Signup and view all the answers

    If a positive number is represented in n-bit two's complement, what can be concluded about its sign bit?

    <p>It will always be 0</p> Signup and view all the answers

    What is the effect of performing arithmetic operations that cross the endpoints of the number circle in two's complement?

    <p>It may lead to incorrect answers</p> Signup and view all the answers

    When adding a positive integer and a negative integer in two's complement, which outcome is guaranteed?

    <p>The result will be representable with available bits</p> Signup and view all the answers

    What is the two’s complement representation of -2 in a 4-bit binary system?

    <p>1110</p> Signup and view all the answers

    How do you determine the decimal value of a binary number represented in two’s complement?

    <p>If the leftmost bit is 1, flip the bits, add 1, and negate the result.</p> Signup and view all the answers

    What is the two’s complement binary representation of +5 in 5 bits?

    <p>00101</p> Signup and view all the answers

    What is the result of adding 1 to the flipped bits of 00111 when finding -7 in two's complement?

    <p>11001</p> Signup and view all the answers

    If the two’s complement binary value is 1010, what is its decimal value?

    <p>-6</p> Signup and view all the answers

    What is the total number of distinct values represented in a signed n-bit two's complement system?

    <p>2^n</p> Signup and view all the answers

    What must be done to represent a negative decimal value 'A' in two’s complement?

    <p>Flip the bits of the binary representation of +A and then add 1.</p> Signup and view all the answers

    Given the binary value 11100 in two's complement, what is its decimal equivalent?

    <p>-12</p> Signup and view all the answers

    What is the decimal value of the octal number 27?

    <p>-9</p> Signup and view all the answers

    What is the result of adding the binary numbers 00101 and 00110?

    <p>11</p> Signup and view all the answers

    In converting the hexadecimal number 1D to decimal, what bit representation is used?

    <p>011101</p> Signup and view all the answers

    When adding two’s complement values, what happens to the carry out of the most significant bit?

    <p>It is discarded.</p> Signup and view all the answers

    If applying two's complement to the binary number 00110, what is the flipped version?

    <p>11010</p> Signup and view all the answers

    What is the decimal equivalent of the unsigned binary number 011101?

    <p>29</p> Signup and view all the answers

    How is the value 2^m related to the operation of adding two binary numbers?

    <p>It determines the modulo to discard.</p> Signup and view all the answers

    In Two's complement addition, what is the result of adding +7 and -2?

    <p>5</p> Signup and view all the answers

    What is the two's complement representation of the number 0?

    <p>00000</p> Signup and view all the answers

    What happens when you add two positive numbers and the result is negative in two's complement?

    <p>An overflow condition has occurred.</p> Signup and view all the answers

    What is the result of adding 5 and 14 in two's complement with 5 bits?

    <p>-13</p> Signup and view all the answers

    To compute D = Y - X using two's complement, what is the first step?

    <p>Flip the bits of X and add 1</p> Signup and view all the answers

    What is indicated when an overflow register is activated during addition?

    <p>Both numbers were positive.</p> Signup and view all the answers

    Which situation will NOT generate an overflow when performing addition in two's complement?

    <p>Adding a positive number to a negative number.</p> Signup and view all the answers

    What is the final step when using two's complement to find the negative of a binary number?

    <p>Add 1 after flipping the bits.</p> Signup and view all the answers

    What representation is used to indicate both 0 and –0 in two's complement?

    <p>00000</p> Signup and view all the answers

    Study Notes

    Signed Number Representations

    • Unsigned number representations offer 2^m unique patterns for m binary digits, while signed representations divide these into positive and negative patterns.
    • Common techniques for signed number representation include sign/magnitude, two’s complement, and binary coded decimal.

    Sign/Magnitude Notation

    • Utilizes the leftmost (most significant) bit as the sign bit: 0 for positive and 1 for negative.
    • Remaining m-1 bits represent the magnitude in unsigned binary.
    • Results in two representations for zero: positive zero (0000) and negative zero (1000), complicating equality checks in computing.

    Two’s Complement Method

    • Based on modular arithmetic; allows representation of signed quantities using n bits.
    • For positive integers, the sign bit is 0 and the remaining bits represent the magnitude.
    • Negative integers utilize 1 as the sign bit and adapt the remaining bits to allow for straightforward arithmetic operations.
    • Formula for value calculation:
      • Val = -2^(n−1) * An−1 + Σ(2^i * Ai) for i = 0 to n-2.
    • Two's complement ensures a single representation for zero and simplifies arithmetic operations.

    Shortcut for Two’s Complement Conversion

    • For positive A:
      • Use sign-magnitude representation with the leftmost bit as 0.
    • For negative A:
      • Calculate binary for +A.
      • Flip bits and add 1 to derive two's complement.

    Checking Decimal Value from Two’s Complement

    • If the leftmost bit (sign bit) is 0, interpret as positive; compute as unsigned binary.
    • If the sign bit is 1, flip bits, add 1, and treat as negative.

    Arithmetic Operations

    • Rules for binary addition simplified to a 2x2 table.
    • Hardware adder processes two binary numbers using bitwise addition and handles carries effectively.
    • Example of adding +7 (00111) and -2 (11110 after conversion) results in valid arithmetic without requiring special sign considerations.

    Handling Overflow

    • An overflow condition occurs when adding two large numbers exceeds the maximum representable value.
    • Check for overflow by assessing two positive numbers resulting in a negative value or two negative numbers resulting in a positive value.

    Performing Subtraction

    • Subtraction is executed by converting to addition of the negative counterpart.
    • To find D = Y - X, compute D = -X + Y by flipping bits of X and adding 1.

    Summary of Arithmetic Results

    • Addition results should discard overflow bits, tracking carries with a carry register while monitoring for overflow conditions with an overflow register.

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    Quiz Team

    Description

    This quiz focuses on signed number representations in computer science, building upon the concepts of unsigned number systems. You will explore the limitations of representing signed quantities and how they relate to binary digits. Test your understanding of these fundamental concepts in the context of digital systems.

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