What does the COMPRESS function remove if no characters are specified?

The COMPRESS function in SAS is specifically designed to remove specified characters from a string. When no characters are indicated, the function defaults to removing all blanks from the input string. This means that any space characters, such as those represented by a spacebar, are eliminated from the data, condensing the string into a more compact form without spaces.

This behavior is particularly useful in data cleaning and formatting processes where excessive whitespace might interfere with subsequent data analysis tasks. The ability to remove just the blank spaces can help maintain the integrity of the text while still capturing all other characters, including punctuation, digits, and letters.

The other options focus on removing specific types of characters (punctuation, digits, or uppercase letters), which are not impacts of the COMPRESS function when no characters are specified. Instead, the function’s default action is to target and eliminate only blank spaces from the text string.