Advances in technology have reduced many of these limitations, and mobile computing is closer to reality than ever before. Mobile computing devices are becoming smaller, lighter, and more powerful than their predecessors. They also come in various types and connectivity options. Two prominent classes of mobile computing devices today are those that use the PalmOS and the PocketPC operating systems. The former class of devices holds a dominant share of the market whereas the latter is growing in market size and is especially popular with executives in business organizations. Often referred to as palmtop computers or handheld computers, these devices are capable of simple word processing, spreadsheet applications, web browsing, calendar notations, and address management. There are low-end handheld computers with monochromatic displays, low resolution, limited memory, and somewhat bulky sizes. Higher-end devices are extremely thin, have a high-resolution, and can include color displays.