Where cannot a block comment begin in SAS?

A block comment in SAS, which is denoted by /* to start and */ to end, can begin at various positions within the code, but there are some restrictions on its placement. The reason why the correct choice specifies that a block comment cannot begin on the first line of a file relates to how SAS processes statements.

When SAS compiles a program, it expects the first line to contain valid executable code or a valid declaration. If a block comment begins here, it would not conform to SAS’s syntax expectations, leading to a compilation error. Hence, positioning a comment on the first line disrupts the flow of the code.

In contrast, placing a block comment in the middle of a line or after a data statement is perfectly acceptable. Comments can be used to annotate or describe code without interfering with its execution. Similarly, inserting a block comment at the end of a DATA step is also valid as it does not affect the SAS processing of the preceding lines. Thus, the uniqueness of the first line’s requirement makes it the only position where a block comment cannot appropriately commence.