One of the most important roles 0 serves in our number system is as a placeholder. Without 0 or an equivalent placeholder, we would not be able to tell the difference between 102, 12, and 1,002. In this positional number system, we use zeros to indicate that there are no tens in the case of 102, and, similarly, that there are no tens or hundreds in 1,002.
To get a better understanding of what simple operations would be like without 0, try to solve the following problems using Roman numerals!
The values of Roman numerals are as follows: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1,000. The numerals are written from largest to smallest and then added, with one exception: Writing a smaller number before a larger one means the smaller should be subtracted from the larger; this happens because four of the same numeral cannot occur consecutively in Roman numberals. In other words, IV (not IIII) represents 4; IX (not VIIII) represents 9; and XL (not XXXX) represents 40. The year 1066 is represented as MLXVI, while 1492 is MCDXCII.
You can quickly see that performing the above computations with Roman numerals is a nearly impossible task!