What's with all these pre-installed apps, and can you delete them?

Pre-installed apps such as calendars and e-mail programmes are designed to keep consumers in a smartphone manufacturer's ecosystem.

There are plenty of useful apps out there. But the ones that come pre-installed on a smartphone generally don't fit into that category. Many are of doubtful value, and some might even pose a security risk. So why are they there?

"It's about differentiation and customer loyalty," says Mark Schulte, an analyst with market researcher IDC. "Manufacturers are trying to offer their customers add-ons that are valuable for everyday use and therefore make themselves stand out."