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The kernel makes its services available to the application programs that run on it through a large collection of entry points, known technically as system calls.

From a programmer's viewpoint, these look just like ordinary function calls, although in reality a system call involves a distinct switch in the operating mode of the processor from user space to kernel space. Together, the repertoire of system calls provides a 'Linux virtual machine', which can be thought of as an abstraction of the underlying hardware.

An even less visible function of the kernel, even to programmers, is memory management. Each process runs under the illusion that it has an address space (a valid range of memory addresses) to call its own.

So, to avoid problem #3b: Just remember that what Linux seems to be now is not what Linux was in the past. The largest and most necessary part of the Linux community, the hackers and the developers, like Linux because they can fit it together the way they like; they don't like it in spite of having to do all the assembly before they can use it.

So whilst vi has an interface that is hideously unfriendly to new users, it is still in use today because it is such a superb interface once you know how it works. Firefox was created by people who regularly browse the Web. The Gimp was built by people who use it to manipulate graphics files. And so on.

However, there is an important difference between a FOSS programmer and most commercial software writers: The software a FOSS programmer creates is software that he intends to use. So whilst the end result might not be as 'comfortable' for the novice user, they can draw some comfort in knowing that the software is designed by somebody who knows what the end-users needs are: He too is an end-user. This is very different from commercial software writers, who are making software for other people to use: They are not knowledgeable end-users.