When dealing with software, we need to remember that what we actually value is not the product by itself, but a series of products that complement one another; in fact, the software is simply one of the parts of the system that we actually use.
It is common to see complementarities in products and services related to ICTs.
Complementary products
There are televisions with very diverse levels of quality, but even the best television is a completely useless appliance if we have no connection to television channels, DVD player, etc.
The complementarity of computer equipment
Similarly, we do not simply want a computer (taking "computer" to mean the physical object, as we saw above with the television), we also want the physical objects that complement the computer, such as printers, digital cameras, scanners, etc. And all these physical objects are not enough; we also need software. We need to have everything that will make the computer run (i.e. the operating system), along with the software we call applications, which allow us to use the computer to perform different tasks. Examples of application software include office automation packages, Internet browsers, e-mail, etc.
Therefore, the complementarity of the various products that make up a system in any digital technology (not only the computer) means that each element of the system in isolation does not really serve much purpose. Naturally, this means that it is essential for these different parts to fit each other and to work properly as a whole, i.e. the various components need to be compatible with one another.