A decimal number is a number that uses the `base-10`

numbering system. This means that each digit in a decimal number represents a power of 10. For example, the number 1234 is a decimal number because it can be represented as:

$1 \times 10^3 + 2 \times 10^2 + 3 \times 10^1 + 4 \times 10^0$

In this representation, the first digit (1) represents 1,000 ($10^3$), the second digit (2) represents 200 ($2 \times 10^2$), the third digit (3) represents 30 ($3 \times 10^1$), and the fourth digit (4) represents 4 ($4 \times 10^0$). When you add these values together, you get the decimal number 1234.

$1 \times 10^3 + 2 \times 10^2 + 3 \times 10^1 + 4 \times 10^0 = 1000 + 200 + 30 + 4 = 1234$

In addition to decimal numbers, there are other numbering systems, such as binary and hexadecimal, that are used in computing. However, decimal numbers are the most commonly used numbering system in everyday life and in computing.

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