Different between Signed and Unsigned characters in C

In C programming, characters are represented using the char data type. However, C provides variations of characters known as signed and unsigned characters, each with its own characteristics and implications. In this article, we will explore the differences between signed and unsigned characters in C, their applications, and considerations for their usage.

Signed and Unsigned Characters

Before diving into the specifics of signed and unsigned characters, let’s establish a foundation by defining these concepts:

  • Signed Characters: Signed characters can represent both positive and negative values. They use a sign bit to indicate the character’s polarity.
  • Unsigned Characters: Unsigned characters, on the other hand, can only represent non-negative values. They do not use a sign bit and are always interpreted as positive.

Storage and Range Differences

One of the key distinctions between signed and unsigned characters lies in their storage size and the range of values they can represent:

  • Signed Characters: Signed characters are typically stored using a two’s complement representation, which reserves one bit to indicate the sign. This affects their range as follows:
    • A signed character can represent values from -128 to 127, as it uses 8 bits of storage.
  • Unsigned Characters: As unsigned characters do not use a sign bit, they have a larger range of positive values:
    • An unsigned character can represent values from 0 to 255, utilizing the same 8 bits of storage.

Choosing Between Signed and Unsigned Characters

When deciding whether to use signed or unsigned characters in your C programs, consider the following guidelines:

  • Character Representations: If you need to represent characters that are specific to your application and can include negative values, signed characters are appropriate.
  • ASCII Characters: If you are working with ASCII characters, which are typically non-negative and fall within the range of 0 to 127, unsigned characters can be used.
  • Compatibility: Ensure compatibility with libraries or APIs that might expect a specific character representation (signed or unsigned).

Usage Scenarios

Let’s explore some common scenarios where the choice between signed and unsigned characters is relevant:

  • Text Processing: Signed characters are commonly used for text processing, as they can represent standard ASCII characters and extended character sets.
  • Binary Data: When working with binary data or non-textual data, such as image or audio files, unsigned characters are typically used.
  • Number Representations: In cases where characters are used to represent numerical values, such as in numeric calculations or encoding schemes, the choice between signed and unsigned depends on the range of values required.


Understanding the difference between signed and unsigned characters is essential in C programming. Signed characters provide the ability to represent positive and negative values within a limited range, while unsigned characters focus on non-negative values with a wider positive range. By considering the specific requirements and nature of the characters you are working with, you can make an informed decision on whether to use signed or unsigned characters in your C programs, ensuring accurate representation and interpretation of character data.