A truly universal machine could take any kind of stuff and do anything with it. You could feed it a paper clip and have a goat come out. You could tell it your name and have it tell your birthday. Universality refers to the kind of materials a machine works with, and the kinds of operations it can do on those materials. At first glance, computers are not universal at all. We have established that the only kind of material they can work with is information in the on/off format, and they can only do a handful of operations to that information. Rather than being universal, these characteristics imply that computers are very limited in their capabilities.
In a sense, they are very limited. But modern computers are capable of beginning to overcome this limitation by sheer size and speed. The earliest computers could do very basic operations only on ones and zeroes. Later machines had more capability. They still could do only rudimentary tasks, but they had made enough advances in memory capacity and speed that these operations could be combined into more complex operations. For example, early computers could add. By repeated addition, they could also multiply, but the multiplication was slow because the addition was slow. As the computers became faster, repeated addition became quick enough to really be thought of (by human users) as multiplication. The process did not change, but the speed of the computer made it seem more powerful.
Likewise, increases in the memory capacity of computers has dramatically improved the variety of information that can be stored in them. Integers are one of the most simple forms of information, so even the earliest computers were able to work with them efficiently. More complex types of information that can be distilled down to integers (such as sound files, graphics, and videos) are not much more complex for the computer to work with, but take up so much space that the early computers could not handle them. Today's