What is the output of the UPCASE function?

The UPCASE function in SAS is specifically designed to transform all the letters in a character string to uppercase. When applied, it scans the input string and converts every lowercase letter (from A to Z) to its corresponding uppercase form, while leaving uppercase letters, digits, and special characters unchanged. This means that if you input a string like "Hello World", the output will be "HELLO WORLD", demonstrating the function's purpose clearly.

The other responses describe functions or transformations that do not align with the action of the UPCASE function. For instance, converting a string to lowercase corresponds to the LOWCASE function, capitalizing only the first letter relates to styling functions like PROPER, and removing special characters indicates potential use of functions like COMPRESS. Thus, the definition of the UPCASE function aligns solely with the transformation to uppercase letters.