Institute of Information Science - University of Miskolc

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===== Floating-Point Representation =====

Floating-point representation is used to store real numbers, especially when dealing with very large or very small values. It approximates real numbers in a way that balances precision and range.

==== The IEEE 754 Standard ====

The IEEE 754 standard is the most common way to represent floating-point numbers. It splits a floating-point number into three components:

  * **Sign (S)**: Determines if the number is positive or negative (1 bit).
  * **Exponent (E)**: Represents the number range (8 bits for single-precision).
  * **Mantissa (M)** (also called the significant or fraction): Represents the precision (23 bits for single-precision).

The formula:

$$ \text{value} = (-1)^S \times 1.M \times 2^{(E - \text{Bias})} $$

where **Bias** is 127 for single-precision (32-bit).

==== Single-Precision (32-bit) Example ====

Let’s break down the number **10.25** in binary to see how it’s represented:

  * **Step 1**: Convert **10.25** to binary:
    * Integer part: **10** in binary is **1010**.
    * Fraction part: **0.25** is **0.01** in binary.
    * So, **10.25** in binary is **1010.01**
  * **Step 2**: Normalize it into scientific notation in binary:

$$ 1010.01 = 1.01001 \times 2^3 $$

  * **Step 3**: Identify the components:
    * **Sign (S)**: 0 (positive)
    * **Exponent (E)**: We add the bias (127) to the actual exponent (3), so **E = 3 + 127 = 130**. In binary: **10000010**
    * **Mantissa (M)**: We drop the leading 1 from **1.01001**, so the mantissa is 010010... (with trailing zeros to make 23 bits)

  * **Step 4**: Combine them
$$ 0 | 10000010 | 01001000000000000000000 $$

==== Special Values in Floating-Point Representation ====

In the IEEE 754 floating-point standard, certain special values are reserved for //edge cases// such as **zero**, **infinity**, and **undefined operations**. These values help systems represent situations that can’t be expressed as regular floating-point numbers.

=== Special Values Overview ===

  * **Zero**: Represents positive or negative zero
  * **Infinity**: Represents positive or negative infinity, resulting from overflow or division by zero.
  * **NaN (Not a Number)**: Represents undefined results, such as **0/0** or **sqrt(-1)**

^ Value ^ Sign Bit (S) ^ Exponent (E) ^ Mantissa (M) ^ Description ^ 
| +Zero | 0 | 00000000 | 00000000000000000000000 | Represents positive zero | 
| -Zero | 1 | 00000000 | 00000000000000000000000 | Represents negative zero | 
| +Infinity| 0 | 11111111 | 00000000000000000000000 | Represents positive infinity | 
| -Infinity| 1 | 11111111 | 00000000000000000000000 | Represents negative infinity | 
| NaN | 0 or 1 | 11111111 | Non-zero value | Represents "Not a Number", used for undefined operations |

Try them out here: https://www.h-schmidt.net/FloatConverter/IEEE754.html