Positive and Negative Numbers - 8.2.1 | 8. Hexadecimal Representation | Computer Organisation and Architecture - Vol 1
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Interactive Audio Lesson

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Introduction to Binary Numbers

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0:00
Teacher
Teacher

Today, we will discuss how numbers are represented in binary. Can anyone tell me what an 8-bit number can represent?

Student 1
Student 1

I think it can represent numbers from 0 to 255!

Teacher
Teacher

That's correct! An 8-bit number can hold 256 unique combinations, ranging from all 0s to all 1s. Remember, this is essential in digital systems.

Student 2
Student 2

What if we want to include negative numbers?

Teacher
Teacher

Great question! To represent negative numbers, we need special techniques. We will explore the Sign Magnitude and Two's Complement methods later.

Student 3
Student 3

Is there a shortcut to remember the maximum range of values an n-bit number can represent?

Teacher
Teacher

Yes! For an n-bit number, you can use the formula 2^n - 1 to find the maximum positive number. This applies only for unsigned integers.

Teacher
Teacher

To summarize, an 8-bit binary number consists of 256 combinations ranging from 0 to 255, which is fundamental for representing integers in computers.

Sign Magnitude Representation

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Teacher
Teacher

Now that we understand binary, let's discuss Sign Magnitude. Who can explain how it works?

Student 4
Student 4

Doesn't it use one bit for the sign and the rest for the value?

Teacher
Teacher

Exactly! The first bit is the sign bit; 0 indicates a positive value, while 1 indicates a negative value. For instance, how would we represent +18 and -18?

Student 1
Student 1

I think +18 would be 00010010 and -18 would be 10010010?

Teacher
Teacher

Correct, but there is a limitation: both +0 and -0 can be represented. This complicates things!

Student 2
Student 2

Can we always use the Sign Magnitude system for calculations?

Teacher
Teacher

Not always. The next representation, Two's Complement, is much better for arithmetic operations.

Teacher
Teacher

So remember, Sign Magnitude uses one bit for sign and is simple but has issues with two representations of zero.

Two's Complement Representation

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Teacher
Teacher

Let's dive into the Two's Complement. Can anyone tell me how we find the two's complement of a number?

Student 3
Student 3

We flip the bits and then add one?

Teacher
Teacher

Absolutely! For a binary number like 00000011, flipping gives us 11111100, and adding one results in 11111101, which represents -3 in decimal.

Student 4
Student 4

Why is Two's Complement useful?

Teacher
Teacher

Two's Complement allows us to perform addition and subtraction without requiring separate circuitry for subtraction. It provides a seamless way to handle negative numbers!

Student 1
Student 1

So can we just add positive and negative numbers directly?

Teacher
Teacher

Exactly! It raises efficiency in computation. Remember that Two's Complement has a range of -128 to 127 for 8-bit numbers.

Teacher
Teacher

To wrap up, Two's Complement is essential for simplifying arithmetic operations with negative numbers!

Overflow and Limitations

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Teacher
Teacher

Now let's discuss overflow. What does this term mean when dealing with binary numbers?

Student 2
Student 2

Is it when you exceed the maximum representable value?

Teacher
Teacher

Exactly! When we add numbers and the result exceeds the limits of what can be expressed in 8 bits, that's overflow.

Student 3
Student 3

What would happen if I add 7 + 7 in 4-bit binary?

Teacher
Teacher

Good question! In 4 bits, 7 is 0111. So, 0111 + 0111 gives 1110, which is actually -2 due to overflow! So we need to be careful.

Student 4
Student 4

How do we detect overflow?

Teacher
Teacher

Great! We look at the carry into and out of the sign bit (most significant bit). If these differ, it's an overflow situation!

Teacher
Teacher

In summary, be cautious of overflow when adding binary numbers, as miscalculations can lead to incorrect values.

Introduction & Overview

Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.

Quick Overview

This section introduces the concepts of positive and negative numbers in the context of binary and hexadecimal systems.

Standard

The section explores how positive and negative integers are represented in computer systems using 8-bit numbers and discusses the importance of hexadecimal representation to simplify the notation of binary numbers. It covers the methods of sign magnitude and two's complement for representing negative numbers and highlights the implications of these representations, including limitations and overflow issues.

Detailed

Detailed Summary

This section delves into the representation of positive and negative numbers in computers, focusing on key concepts such as the binary and hexadecimal systems. In binary, numbers can take on both positive and negative values, each with specific bit patterns. For instance, an 8-bit binary number can represent a total of 256 values, ranging from 0 to 255 for positive integers. However, when including negative integers, the range of usable positive values decreases.

Two primary methods for representing negative integers are discussed: Sign Magnitude and Two's Complement. Sign Magnitude involves splitting the bit pattern into a sign bit (0 for positive, 1 for negative) and a magnitude portion for the numeric value. Two's Complement, on the other hand, allows for a more efficient representation by using the most significant bit as the sign and allowing for straightforward arithmetic operations, even in subtraction.

An important feature is the handling of overflow situations in calculations with limited bit sizes. It explains how carry bits can indicate overflow, which happens when the result of an operation cannot be represented accurately within the defined limits of the bit size.

In summary, understanding these representations is crucial for comprehending how computers process numerical data, manage binary calculations, and deal with potential overflow in digital systems.

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Audio Book

Dive deep into the subject with an immersive audiobook experience.

Introduction to Number Representation

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So, the similar information I am representing in another number system which is your hexadecimal. Now, you just see what I am saying this is your 8 bit number all 0s to all 1s. So, all 1 in decimal it becomes 255 in hexadecimal it is your FF, FF means 15 F represents 15, 15 × 16^1 + 15 × 16^0. So, in that particular case we will get that this is nothing but 255 in decimal.

Detailed Explanation

This chunk introduces the concept of representing numbers in different numeral systems, specifically the hexadecimal system. It points out that all binary numbers can be represented in hexadecimal to simplify their understanding. For example, an 8-bit binary number can range from all zeros (0) to all ones (255 in decimal or FF in hexadecimal). FF in hexadecimal is calculated by taking 15 (the value of F) multiplied by 16 raised to the power of 1 and 0, which results in 255 in decimal. This representation helps us understand larger binary numbers more easily.

Examples & Analogies

Think of binary and hexadecimal systems as different languages describing the same object. Just as '255' in English can be written as 'FF' in French, binary numbers can also be expressed in hexadecimal for simplicity.

Benefits of Hexadecimal Representation

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Now, when we are going to discuss that representation of number in computer or in your binary system or binary digit most of the time we are going to take help of hexadecimal number system because it is having one advantage. Say, when I am going to work with 32 bit number I have to write 32 bits ok all 32 bits 0 or maybe combination of 0s and 1 which is slightly difficult. Similarly when we are going to work with 8 bits we are going to write 8 bits all 0s to all 1.

Detailed Explanation

This part emphasizes the advantages of using the hexadecimal system in computer science. Hexadecimal can represent larger numbers compactly compared to binary, which requires more bits to express the same value. For instance, instead of writing a long string of binary digits for a 32-bit number, we can use fewer hexadecimal digits to convey the same information effortlessly. This makes reading and managing binary data much easier for programmers.

Examples & Analogies

Imagine trying to write your address in small handwriting on a tiny notepad. It would be hard to read! Now, imagine writing the same address on a postcard using larger text. The postcard is like the hexadecimal system—easier to read and manage than a dense notepad filled with tiny handwriting.

Range of 8-bit Binary Numbers

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Now, say if I am having 8 bit numbers. So, I am having a combination of 0s and 1s and 8 bits 8 symbols. So, in that particular case we are having 256 different symbols or combinations, so this combination will go from 0 to 255.

Detailed Explanation

In an 8-bit system, each bit can be either 0 or 1, resulting in a total of 2^8 or 256 possible combinations. This allows us to represent numbers ranging from 0 to 255. This chunk elucidates how computer memory works in terms of bits and bytes, providing a foundational understanding of how values are stored and processed.

Examples & Analogies

Think of an 8-bit number like a combination lock with eight dials. Each dial can be set to two positions—0 or 1. By turning each dial, you can create 256 different combinations, similar to how different numbers can be represented in 8 bits.

Handling Negative Numbers in Binary

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But if you are going to consider about negative number also this is the number line this is 0 and this is your positive side and this is your negative side. So, when we are going to work with a negative number then what will happen whatever 256 different bit patterns we are having some of the bit patterns need to be reserved for negative numbers also.

Detailed Explanation

This chunk discusses how negative numbers are represented in binary. When considering both positive and negative integers, the range of numbers changes because we need to reserve some combinations for negative values. This limits the positive numbers available, and it highlights the importance of understanding both sides of the number line when dealing with binary representation.

Examples & Analogies

Imagine a balance scale with positive weights on one side and negative weights (representing debt) on the other. Just as your total weight can shift depending on whether there are more positives than negatives, the range of valid numbers in a binary system must reflect this balance between positive and negative values.

Sign-Magnitude Representation

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So, basically we have with 8 bit numbers we can handle 256 different numbers. So, if it is your only positive numbers we are going to deal from 0 to 255, but if we are going to handle negative numbers then range will reduce it will go from some negative 127 to positive 127.

Detailed Explanation

This segment introduces the concept of sign-magnitude representation where a specific bit is allocated for the sign (positive or negative) and the remaining bits for the magnitude of the number. In an 8-bit representation of integers, with one bit for the sign, we can handle numbers ranging from -127 to +127. This explains how the system manages positive and negative values and illustrates the constraints of a fixed binary length.

Examples & Analogies

Think of a thermometer that can only display temperatures from -127°C to +127°C. If a temperature falls outside this range, the thermometer can't accurately represent it—similar to how our binary representation has limitations because of the fixed number of bits.

Two's Complement Method

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So, for that we are having 2 ways of representing this number one is your sign magnitude...but now we are saying that 0 is my indicating the sign with it is a positive number. So, it is +18 and this bit more significant bit is 1, 1 represent the negative numbers.

Detailed Explanation

This chunk explains how the two's complement method allows for a simplified form of representing negative numbers. By using the most significant bit to indicate the sign and allowing for simple arithmetic operations, two's complement has become the standard in computing for representing negative integers. It gives a systematic way of shifting the binary representation for negatives and enables easier calculations.

Examples & Analogies

Consider a rules-based game that requires you to move forward (addition) or backward (subtraction) based on the dice you throw. If the rules allow you to count backward simply by adding a negative score, it makes the game smoother and simpler—just like two's complement simplifies handling negatives in binary arithmetic.

Overflow in Binary Arithmetic

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So, in this particular case whatever result we are getting these are not correct because we have working with 4 bit numbers and you can handle 4 bits only. So, in that particular case these are not the correct result because we know that for 4 bit numbers my range is from -8 to +7.

Detailed Explanation

This section highlights the concept of overflow, which occurs when the calculated result exceeds the range representable by the current number of bits. For instance, if adding two numbers yields a total that is higher than the maximum (7) or lower than the minimum (-8) of a 4-bit system, it results in incorrect readings. This is an important understanding in computer systems to avoid bugs during arithmetic processing.

Examples & Analogies

Picture a jar that can only hold a certain amount of cookies (let’s say 8 cookies). If you try to add more cookies than it can hold, cookies will spill over, leading to a mess! In computers, if calculations exceed the 'jar capacity' of bits, it leads to overflow and incorrect results.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Binary and Hexadecimal Representation: Systems for encoding numerical values in computing.

  • Sign Magnitude Representation: Method of representing both positive and negative integers.

  • Two's Complement: Method for representing negative integers that simplifies arithmetic operations.

  • Overflow Condition: A situation where the result of a calculation exceeds the maximum representable range.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • An 8-bit binary number can represent numbers from 0 to 255. Exceeding this range leads to overflow.

  • Using Two's Complement, the number -1 is represented as 11111111 in binary for an 8-bit system.

  • The decimal numbers +18 would be 00010010 in binary, while -18 is 10010010 in Sign Magnitude representation.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎵 Rhymes Time

  • To count in binary, zeroes and ones, Just flip the bits, until you're done!

📖 Fascinating Stories

  • Imagine a digital town where houses represent numbers; negative houses have signs in their windows. The houses have neighbors just like the binary shifts we make!

🧠 Other Memory Gems

  • Remember 'Flip and Add' to convert to Two's Complement: 'F' for flipping bits and 'A' for adding one.

🎯 Super Acronyms

BINARY

  • 'Bits In Numbers Are Really Yours' - to remember the significance of bits in binary representation.

Flash Cards

Review key concepts with flashcards.

Glossary of Terms

Review the Definitions for terms.

  • Term: Binary Number System

    Definition:

    A numeral system that primarily uses two digits, 0 and 1, to represent values.

  • Term: Hexadecimal

    Definition:

    A base-16 number system that uses symbols 0-9 and A-F to represent values.

  • Term: Sign Magnitude

    Definition:

    A method of representing integers where one bit indicates the sign and the remaining bits indicate the magnitude.

  • Term: Two's Complement

    Definition:

    A mathematical operation on binary numbers where the bits are inverted, and one is added to the least significant bit to represent negative values.

  • Term: Overflow

    Definition:

    A condition that occurs when a calculation exceeds the maximum limit that can be represented in a number system.