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When working with Stata, you will be using what is referred to as a “data file.” If you are familiar with typical database programs, then you already know what a data file basically is. These files contain information (often numerical) on a set of cases, such as respondents to a survey, a sample of schools, or each of the states in the United States. Generally, data files are organized such that information regarding each case is contained in one row in the file, whereas each column represents a variable (i.e., information about that case), such as a person’s gender, a school’s total number of students, or a state’s total square miles.

Similar to most computer files, data files come in many different types. But just as a PDF (portable document format) file is very similar to a word document, so too are all data files essential derivations of a similar structure. Each of these derivations is denoted by a different file extension—the letters that come after the “ . ” in a file name. The primary file for Stata data files is .dta. Moving other types of data files into Stata (e.g., Microsoft Excel files) is covered in the Using Different Types of Data Files in Stata section of this chapter.