A question like “What is a computer?” can be answered from a technical point of view. Theoretical scientists would argue, that a computer is turing machine, while processor experts will say, that it has to do with the assembly mnemonics. In the early 1980s a different answer was given. According to Microsoft, a computer is equal to booting the MS-DOS operating system and start a program. Microsoft was right and as a result they became the most successful company ever.
But is a computer equal to the operating system? And what is with alternative software like Linux? The interesting point is, that it's make sense to see MS-DOS equal to a computer. Because it was the first attempt in that direction. The idea was an additional layer between computer and human was needed. Which means, that without MS-DOS it can't be explained what a computer is. The definition that a computer is a turing machine or has to be programmed in Assembly language is correct too, but it is only a part of the answer.
Let us analyze what MS-DOS 3.0 is exactly. It is a layer, which sits on top of the hardware. It's an environment to run a program. This definition make sense for two parties at the same time. It make sense for the developers who are programming software in C and compile them to run under MS-DOS. But the definition makes also sense for the user, who is typing in a program name and use the computer for writing a letter.
To answer the question from the beginning “What is a computer?”. The answer in the early 1980s was to invent an operating system. And the OS can answer the question. The question contains of a sentence, and the answer was equal to the floppy disk which contains MS-DOS.
Microsoft has answered a specific question. If we are reformulating the question a bit, MS-DOS is no longer the answer. The new question is: what is an open source operating system which supports TCP/IP? The answer to this question was given by Red Hat, not by Microsoft. We can discuss, if this new kind of question makes sense. Why do we need an open source OS, is a normal OS not enough to run games and applications?