Plant extracts

A calculator is a device for performing mathematical calculations, distinguished from a computer by having a limited problem solving ability and an interface optimized for interactive calculation rather than programming. Calculators can be hardware or software, and mechanical or electronic, and are often built into devices such as PDAs or mobile phones. Modern electronic calculators are generally small, digital, (often pocket-sized) and usually inexpensive. In addition to general purpose calculators, there are those designed for specific markets; for example, there are scientific calculators which focus on advanced math like trigonometry and statistics, or even have the ability to do computer algebra. Also graphing calculators can be used to graph equations. Modern calculators are more portable than most computers, though most PDAs are comparable in size to handheld calculators.