nnectivity imply that neither the application nor the content are stored in the device but are downloaded as required on demand. The future of both embedded memory and plug-in memory is thus open to debate. The debate benefits from an understanding of the various solid-state memory options and their relative advantages and disadvantages. 9.5.1 Flash (Nor and Nand), SRAM and SDRAM Flash-based solid-state memory can be configured to look and behave like a hard disk (given its ability to retain data in power down) and has the big advantage of not having any moving parts. It is however, more expensive and comes in a bewildering range of form factors. Embedded nonvolatile (FLASH) memory in a cellular handset is typically a mix of NOR for code storage and NOR and NAND for data storage. NOR sets the input memory state at 0, NAND sets it at 1. NAND costs less than NOR because it takes a number of memory capacitors and matches them to a smaller number of switching transistors. NAND is more error prone but the cost benefits make it a preferred option for most embedded data storage applications. Wear-levelling techniques have also increased the number of write cycles to typically 100 000 or more even on extreme geometry devices. Flash memory, originally developed by Intel, works on the basis of having two transistors separated from each other by a thin oxide layer - one transistor is known as the 'control gate', the other is the 'floating gate'. The floating gate can have its state changed by a process known as tunnelling. An electrical charge is applied to the floating gate transistor that then acts like an electron gun, pushing electrons through the oxide layer. A cell sensor measures the level of charge passing through the floating gate. If it is more than 50% of the charge, the state value Content- and Entertainment-Centric Software is 1, if less than 50%, the value is 0. The gate will remain in this state until another electrical charge is applied. In other words it is nonvolatile. It will retain its state even when po