Decoding Char Values: Why Subtracting '0' Divulges the Numeric Representation

A puzzling question arises: why does subtracting '0' from a character in C reveal the numeric value it represents?

To unravel this enigma, let's delve into the realm of ASCII (American Standard Code for Information Interchange), which assigns numerical codes to each character. '0' holds the first position in this numeric sequence, with subsequent characters incrementally assigned higher values.

For instance, '9' represents the numeric value 57, while '0' corresponds to 48. By subtracting '0' from a character, we essentially calculate the difference between its ASCII code and the ASCII code of '0'.

Consider the example: char c = '9'; int x = (int)(c - '0');
Here, '9' has an ASCII code of 57. Subtracting '0' (which has an ASCII code of 48) yields 57 - 48 = 9, which is precisely the numeric value represented by '9'.

The following ASCII table further illustrates this concept:

By subtracting '0' from any char, we can effectively decode the numerical value it represents, a technique commonly employed in various programming applications.