dummy index notation

例句：

1. 1. This is a common mistake made by beginners in programming.
   这是初学者在编程中常见的错误。
2. 2. The dummy index notation is used to represent variables without actually assigning values to them.
   伪索引符号用于表示变量，而不实际为它们分配值。
3. 3. In this case, the dummy index notation is used to indicate that the variable is not being used.
   在这种情况下，伪索引符号被用来表示该变量未被使用。