When processing an internal table with the LOOP AT statement, which system variable contains the current row number?

The system variable that contains the current row number when processing an internal table with the LOOP AT statement is sy-tabix. This variable is particularly important as it provides the index of the current row being processed within the internal table during iteration.

When you use the LOOP AT statement to iterate over an internal table, sy-tabix automatically updates to reflect the position of the current row. This allows the developer to easily reference the row index within the loop without needing to maintain a separate counter variable. This is especially useful for cases where the loop's processing logic requires knowledge of the current index, such as conditional processing or when updating specific rows based on their index.

In contrast, the other system variables do not provide the current row number in the context of an internal table iteration. For instance, sy-linno generally relates to line numbers in lists or reports, sy-subrc is used to check the success or failure of certain operations (often related to function modules or database operations), and sy-index is used when iterating over a table but does not specifically correspond to the row number in the context of internal tables. This makes sy-tabix the correct choice for identifying the current row number in an internal table while processing it with loop statements.