The programmers of oracle database normally used the sqlplus to write and execute commands like;

SQL > select * from tab;

To display fileno, name, we have to write the command;

SQL > select  file_no,name  from emp;

If we have to add another column, we have to write the whole command again;

SQL > select  file_no,name,sal  from emp;

In sql plus, it is not possible to change/edit the previous commands easily. We have to write the whole command completely or we use the note pad to edit the commands.