PCs: The Missing Manual

Appendix B. Memory Cards and USB Drives

Most people get acquainted with memory cards the first time they buy a digital camera and need some “digital film” to go along with it. Others buy USB drives—memory cards connected to a handy USB plug—to carry around their data and pictures of loved ones.

These digital doohickeys are so convenient that it’s easy to forget about the technological marvel inside: the hidden flash memory that contains special circuits with thousands of tiny switches. When the computer (or camera) saves information to the card, the switches flip into a certain position. To retrieve the information later on, the computer reads the switches’ positions.

The switches stay in place when flipped, letting the card remember its information for about 100 years, at least according to manufacturers’ claims. Count on about a decade or so—more than enough time to dump the information onto your PC. Unlike the main memory inside your computer (also known as RAM), which for-gets its information when your PC’s turned off, flash memory doesn’t require batteries to keep its switches flipped.

This chapter explains the different types of memory cards and USB drives you’re likely to encounter, how to tell them apart, which ones you need, and how to write and read information to and from them.

Memory Cards

Memory cards began life in 1992 as PC Cards. Back then, they provided the only way to boost a laptop’s meager memory: slip a credit card–sized PC Card into the laptop’s PC Card slot, and ...