Signed vs Unsigned: Difference and Comparison

In programming, the terms “signed” and “unsigned” refer to the interpretation of integer data types. Signed integers can represent both positive and negative numbers by dedicating one bit to indicate the sign and the remaining bits to the magnitude. On the other hand, unsigned integers exclusively represent non-negative numbers, utilizing all bits for the magnitude.

Key Takeaways

1. Signed data is verified with a digital signature, which guarantees the authenticity and integrity of the data.
2. Unsigned data does not have a digital signature and is not verified, making it vulnerable to tampering or modification.
3. Signed data is commonly used in secure communications, while unsigned data is used in non-critical applications.

Signed vs Unsigned

Signed and unsigned pertain to how numbers are represented in computer programming. Unsigned numbers are always positive, they can express bigger positive values. Signed numbers can be either positive or negative, they have an equal distribution of positive and negative values.

In computer programming, these ‘signed’ and ‘unsigned’ categories refer to variables that can contain certain types of integers. In the coding context, the former category can hold both types of integers. In contrast, the latter category can solely encompass the number zero and the entire list of positive integers.

Comparison Table

Feature	Signed	Unsigned
Value Range	Can represent positive, negative, and zero values.	Can only represent non-negative (zero and positive) values.
Number Representation	Uses a sign bit (the most significant bit) to indicate the sign (0 for positive, 1 for negative).	Does not use a sign bit, devoting all bits to the magnitude of the value.
Memory Usage	For the same number of bits, the signed type can represent half the range of the unsigned type.	Due to no sign bit, the unsigned type can represent a wider range of values.
Common Use Cases	Representing quantities that can be positive, negative, or zero (e.g., temperature, coordinates, financial transactions).	Representing quantities that are inherently non-negative (e.g., memory addresses, file sizes, counters).
Comparisons	Be careful when comparing signed and unsigned values directly in some programming languages.	Can be compared directly as they occupy the same range of values.

What is Signed?

Signed is a data type attribute used in programming languages to represent integers, used to store whole numbers. The “signed” attribute signifies that a variable can hold both positive and negative values. When a variable is declared as signed, it means that it can represent positive, negative, and zero values. Signed integers are fundamental for arithmetic operations involving both positive and negative numbers.

Representation

In signed integers, the leftmost bit (the most significant bit) is used to denote the sign of the number. If this bit is set to 0, the number is positive or zero, and if it’s set to 1, the number is negative. The remaining bits represent the magnitude of the number, using the standard binary representation.

Range

The inclusion of negative numbers in signed integers affects their range compared to unsigned integers. For instance, in a typical 8-bit signed integer, the range is from -128 to 127. The maximum positive value is limited by one less than the maximum magnitude that can be represented in the given number of bits.

Usage

Signed integers are commonly used when a range of both positive and negative values is required. They are crucial in scenarios such as financial calculations, where values can be positive (income) or negative (expenses). Additionally, signed integers are utilized in algorithms involving arithmetic operations where the result might be negative.

Example

For example, if we have an 8-bit signed integer, its range would be from -128 to 127. If the binary representation of 01111111 (127 in decimal) is considered, it represents a positive value. Conversely, the binary representation of 10000000 (-128 in decimal) represents a negative value due to the leftmost bit being set to 1.

What is Unsigned? 

Unsigned is a data type attribute commonly used in programming languages to represent integers. Unlike signed integers, which can represent positive, negative, and zero values, unsigned integers exclusively represent non-negative values. When a variable is declared as unsigned, it means it can only hold positive or zero values, effectively doubling the range of positive values compared to signed integers.

Representation

In unsigned integers, all bits are used to represent the magnitude of the number, with no bit dedicated to indicating the sign. This means that the leftmost bit (most significant bit) in the binary representation is part of the magnitude, allowing for a greater range of positive values.

Range

The absence of negative numbers in unsigned integers extends their range compared to signed integers. For instance, in an 8-bit unsigned integer, the range is from 0 to 255. The maximum value is determined by the maximum magnitude that can be represented in the given number of bits.

Usage

Unsigned integers are preferred when dealing exclusively with non-negative values. They are commonly used in scenarios where only positive values are relevant, such as representing quantities, array indices, or memory addresses. Additionally, unsigned integers are utilized in bitwise operations and situations where arithmetic operations should not produce negative results.

Example

For example, in an 8-bit unsigned integer, the binary representation of 11111111 (255 in decimal) represents the maximum positive value. Unlike signed integers, there’s no need to allocate a bit to denote the sign, allowing the full range of bits to contribute to the magnitude.

Main Differences Between Signed and Unsigned

• Representation:
  • Signed integers use one bit to represent the sign (positive or negative) and the remaining bits for the magnitude.
  • Unsigned integers use all bits for representing the magnitude, with no bit dedicated to indicating the sign.
• Range:
  • Signed integers can represent both positive and negative values, but the range is limited by one less than the maximum magnitude that can be represented.
  • Unsigned integers exclusively represent non-negative values, allowing for a greater range of positive values compared to signed integers.
• Usage:
  • Signed integers are commonly used when negative values need to be represented, such as in arithmetic operations involving both positive and negative numbers.
  • Unsigned integers are preferred when dealing exclusively with non-negative values, such as representing quantities, array indices, or memory addresses. They are also utilized in bitwise operations and scenarios where arithmetic operations should not produce negative results.

References

1. https://ieeexplore.ieee.org/abstract/document/6606625/
2. https://link.springer.com/chapter/10.1007/978-3-540-28628-8_8
3. https://www.cs.umn.edu/sites/cs.umn.edu/files/tech_reports/14-006.pdf