How many software companies are in Silicon Valley?

[14615]

I know the big ones, like Google, are based there but I hear Silicon Valley mentioned so many times that it looks like all software companies are based there. Anyone know what is the exact number of software companies in Silicon Valley? And why do they choose to have their offices there considering how expensive the area is?

[kcareconnections]

I do not know how many are there. But al least a dozen of the best and largest tech companies are there. There are also thousands of smaller tech companies. This makes it a hot spot for software companies.