Hardware Reference
In-Depth Information
Figure 6.3
Flowcharts illustrating the logic of
DO
...
LOOP WHILE
and
DO
...
LOOP UNTIL
structures. (a)
DO
...
LOOP WHILE
; (b)
DO LOOP UNTIL
respectively. It is important to note that the main body of loop statements within
a
DO
...
LOOP WHILE
or
DO
...
LOOP UNTIL
structure is executed
at least once
whilst the main body of loop statements within a
DO WHILE
...
LOOP
or
DO
UNTIL
...
LOOP
need
never
be executed.
Prompts and messages
Any program to be used by a person other than the originator should incorp-
orate meaningful prompts and messages to aid the user. Prompts should also
give some indication of the input required from the user in terms of the
acceptable keystrokes, the length of an input string, and the need to include
a RETURN keystroke. The following are examples of typical text prompts that
are acceptable for use in a DOS Window or a total DOS environment:
Do you wish to quit? (Y/N)
Press [SPACE] to continue.
Enter today's date (MM:DD:YY) followed by [RETURN]
Enter filename (max. 8 characters) followed by [RETURN]
Messages, unlike prompts, demand no immediate input from the user and
should be included at any point in the program at which the user may require
information concerning the state of the system. Messages should be written in
