Why are large commercial companies interested in developing mobile apps for smartphones?

because they can
because it is trendy
because they can make a lot of money if they create a popular application
because this is the most suitable way to utilize their recently hired programmers

Each time you save a document, you will need to type in the file type in which it should be saved you can select the save button to save it with the same file name if it has been previously saved you will need to select the location to save the file you will need to use the save as dialog box