When the program requires input from a file that is associated with a terminal, it issues a prompt. This takes the form of printing a colon on the next line and then skipping to column 1 on the line following the colon. This gives you a full line to enter your input, as follows:
: (space for entry of your data)
This type of prompt is referred to as a primary prompt.
You can override the primary prompt by making a colon the last item in the request for the data. You cannot override the secondary prompt. For example, the two PL/I statements:
PUT SKIP EDIT ('ENTER TIME OF PERIHELION') (A);
GET EDIT (PERITIME) (A(10));result in the terminal displaying:
ENTER TIME OF PERIHELION : (automatic prompt) (space for entry of data)
However, if the first statement has a colon at the end of the output, as follows:
PUT EDIT ('ENTER TIME OF PERIHELION:') (A);the sequence is:
ENTER TIME OF PERIHELION: (space for entry of data)