Understand the pre-increment (`++i`), post-increment (`i++`), pre-decrement (`--i`), and post-decrement (`i--`) operators.
The increment (`++`) and decrement (`--`) operators in C are unary operators that provide a concise way to increase or decrease the value of a variable by one. They are very commonly used, especially in loops. Each operator comes in two forms: prefix and postfix. The prefix form (`++var` or `--var`) modifies the variable's value *before* the expression is evaluated. So, if you have `y = ++x;`, the value of `x` is first incremented by one, and then this new value is assigned to `y`. After this statement, both `x` and `y` will hold the same incremented value. The postfix form (`var++` or `var--`) modifies the variable's value *after* the expression is evaluated. If you have `y = x++;`, the original value of `x` is assigned to `y` first, and only then is `x` incremented by one. After this statement, `y` will hold the original value of `x`, while `x` will hold the incremented value. The distinction between prefix and postfix is crucial when these operators are used within a larger expression, as it affects the value that is used in the rest of the calculation. However, when used as a standalone statement, like `i++;` or `++i;`, both forms have the exact same effect: they simply increment `i` by one. While these operators are convenient, using them multiple times on the same variable within a single complex expression can lead to undefined behavior, so it's best to use them in a clear and straightforward manner.