Think about how you search for files on your hard disk. You most likely use the ? and * characters to find files. The ? character matches a single character in a file name, while the * matches zero or more characters. A pattern such as 'data?.dat' would find the following files:

data1.dat

data2.dat

datax.dat

dataN.dat

Using the * character instead of the ? character expands the number of files found. 'data*.dat' matches all of the following:

data.dat

data1.dat

data2.dat

data12.dat

datax.dat

dataXYZ.dat

While this method of searching for files can certainly be useful, it is also very limited. The limited ability of the ? and * wildcard characters give you an idea of what regular expressions can do, but regular expressions are much more powerful and flexible.