Chapter One
A Tab Left Open
Imagine you are writing a sentence while a call waits in a small window at the edge of your screen. There is a browser tab with a timetable, another with a map, and an image you opened to check one detail. You move the cursor back to the sentence. It is still there. The ordinary miracle is not that the computer has saved all this forever. It is that so much unfinished work can remain ready at once.
The processor is usually given the credit for feeling quick. A processor does the calculating and follows instructions, so it deserves some. Yet even a fast worker becomes idle if every needed page of information must be fetched from a distant store. A computer therefore keeps active data in working memory. The dominant technology for that large working space is dynamic random access memory, or DRAM. It is probably hidden under a plain cover or soldered inside the device you are using. You may know it only as RAM.
That last word causes a surprising amount of confusion. RAM names a broad way of accessing information. DRAM names a particular technology used for much of a computer's main working memory. A memory module in a desktop usually carries several DRAM chips. The module is a board and a connection, not a different substance. In a phone, the package may look different and be placed close to the processor, but it is still part of the DRAM family. When an advertisement says a computer has more RAM, it is generally telling you about how much working data the machine can keep in reach.
