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Every file on a computer is just 0 and 1s.
File extensions tell us how to interpret the 0s and 1s.
The file extension refers to the part of the file
that appears after the dot:
We can divide up every file extension into two classes of files:
text files can be opened and read with just a plain text editor (Notepad++, TextWrangler, etc)
binary files are encoded and requires a special-purpose program to open
There are two common, near-universal formats for data:
A comma separated values file is a text file with the extension csv.
Each line represents a row of data.
Within each line, values are separated by commas.
"MSFT",42.36 "AAPL",126.60 "GOOG",567.68
Excel files (xls, xlsx) are spreadsheets.
Spreadsheets organize data into 2D grids, with the ability to add formulas, styles, graphs, and other features.
Excel is not the only spreadsheet tool: