Every program accepts data from the outside world, manipulates that data in some way, and then calculates a useful result. Data can be

**Numbers****Text****Input from a keyboard, controller, or joystick (for a video game)**

To manipulate numbers, computers can perform a variety of mathematical operations, which is just a fancy way of saying a computer can add, subtract, multiply, and divide. To manipulate text (or *strings*, as in "text strings"), computers can perform a variety of string manipulation operations, which can chop out a letter of a word or rearrange the letters that make up a word.

Every programming language provides built-in commands *(operators)* for manipulating numbers and strings, but some programming languages are better at manipulating numbers (or *strings*) than others.

For example, FORTRAN is specifically designed to make scientific calculations easy, so FORTRAN has more operators for mathematical operations than a language such as SNOBOL, which was designed primarily for manipulating text strings. You can still manipulate strings in FORTRAN or calculate mathematical equations in SNOBOL; however, you need to write a lot more commands to do so.

Programming languages typically provide two types of data manipulation commands:

**Operators**are usually symbols that represent simple calculations, such as addition (`+`

) or multiplication (`*`

).**Functions**are commands that perform more sophisticated calculations, such as calculating the square root of a number.Unlike ...

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