A calculator is a device that performs arithmetic operations on numbers. The simplest calculators can do only addition, subtraction, multiplication, and division. More sophisticated calculators can handle exponential operations, roots, logarithms, trigonometric functions, and hyperbolic functions. Internally, some calculators actually perform all of these functions by repeated processes of addition.

In the modern world, some pocket calculators are so powerful that they are really computers in their own. Many come with powerful programming capablities and graphics. The rapid development of different calculators make calculations faster and more convenient. In the following, special functions of different kinds of calculators are introduced.

1. Basic Scientific Calculators: 

Scientific calculators offer, in addition to the basic arithmetic operations, transcendental functions such as sines, logarithms and powers. These functions are computed as required by the calculator using series expansions. Before calculators were available, you would have looked these functions up in tables (to a much more limited accuracy). They are heavily used by mathematics, science and engineering students. In addition, these devices usually include a range of statistical functions to compute means and standard deviations, combinatorial calculations and possibly linear regression. Most can also convert between different number bases and apply logic operators such as AND and XOR. These are especially useful to people working with computers and logic design. The number of functions means that calculator designers have had to assign two or more of them to each button, which makes it look fairly complicated when compared to a simple arithmetic calculator. Because of the demand from school students, calculators in this category are produced in large numbers (with several million sold worldwide each year) and consequently the prices are relatively low.

2. Advanced Scientific Calculators: 

Some manufacturers have tried to make scientific calculators easier to use by having a two-line display. An algebraic * style expression is entered on one line and the answer can be displayed on the second line. The advantage is that the expression can be edited and the result re-calculated. The user has to observe the correct syntax, however, some users prefer the conventional style of calculator. Other features in these advanced scientific calculators are fractions and programmability. The programmables can be given a sequence of instructions for complex calculations which are frequently used. In practice, programming is quite difficult using the limited language and display capabilities of pocket calculators and tends to resemble programming in assembly code. If you need to write programs, it probably makes more sense to use a computer.

3. Graphing Scientific Calculators: 

Graphing calculators allow you to display an expression in graphical form. This tends to be of most use in education where a student can quickly display a trancendental function or expression, which helps in understanding. The effect of changing parameters in the expression can also be observed. This has made graphing calculators very popular in education. It has to be said that for graphical output the displays on these devices are quite limited, with a resolution considerably less than most PDAs. If you need to plot real data, for example, you will probably want to use a computer. The larger display size of the graphing calculators, whilst of limited use for curve plotting, makes it possible for the designers to add additional ease-of-use features, and so most of these calculators include some kind of menu system. This also means that more features can be added without further adding to the complexity of the calculator key layout. Most graphing calculators are also programmable, and the larger display makes programming easier and allows programs to interact with the user more effectively. Many calculators also have an optional connector to exchange data and software with a computer, which allows you to download software from the Internet. 

4. Financial Calculators: 

Financial calculators are designed for people working with money, particularly those making investment decisions over long periods where the time value of money becomes significant. The classic financial calculator of the 1980’s was the HP12C, which is still made, albeit with updated electronics. The most important application in financial calculators is the time value of money. In essence, the calculator solves for the initial amount, interest (or discount) rate, the final amount, the number of periods, and the repeating payment (possibly zero). You can input all of these values with the exception of one, which the calculator then solves for. This allows you to compute all kinds of mortgages, leases and investments. Other features are typically date functions, depreciation and bond and option calculations. Most financial calculators are programmable, but as for the programmable scientific calculators, programming is not easy with a limited display and programming language. However, the manufacturers often supply useful pre-written software for solving more complex problems. 

5. Others: There are some modem calculators which can combine all these functions listed above, and they are called multi-functional calculators.