Once a program is typed, you must submit it before you can get any results. After a program has been submitted, you must recall your program back into the program editor. A data set must be entered prior to any data manipulation, but additional data may be entered at any time in a SAS program. This makes it much easier to debug your SAS program, since previous comments are erased. The second statement adds a title to the top of every page of output.
Titles are very important, especially in large programs.
The third statement allows you to specify options. Most options are self explanatory, but ls changes the size of a line of text and ps changes the amount of lines on a page, which can be very important with some printers. It is usually important to choose variable names that are short, yet descriptive. The fourth statement creates a new variable A rea by manipulation the data that has been entered. The final statement tells SAS that the data will follow.