Program-Line Review Keys - Sharp PC-1500A Instruction Manual

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Now run the revised program. What happens? Press l•••ul alter "JOLLY" appears.
Notice in this example both what SHARP has done for you and what you have had to do for
yourself. SHARP has arrangt'CI and executed lines 5 and 10 in the proper order. Yet, to nudge
SHARP on from line 5 to 10, to see the result of line 10, you have to press ENTER between
outputs.
Although a line number may be any number from
1
to 65,279, we strongly advise you to
number your lines by increments of 10 (i.e. 10, 20, 30, · · · etc.). This allows you to insert up to
9 statements between your current statements {11 through 19. for instance}. Some programmers
recommend an even greater gap; numbering by 20's. Although, with careful program design and
writing, you will ra rely need to insert statements, do not count on this! It is far easier to nur11ber
by 1 O's now than to renumber many statements later.
Remember that no two lines may have the same line number. If this condition should occur,
the oldest line (the one entered first) will be lost. Th is feature can be exploited to delete
unwanted lines merely by keying the line number .af the line to be deleted and pressing l<••••I .
Thus, an empty, yet numbered, line will effectively delete an existing line with the same number.
If duplicate line numbers are used unintentionally, however. trouble will resu lt . To
demonstrate this, enter the following line (in PROgram mode, of course):
Keystrokes:
rn ca
1
m mmoo m
'"''"1
c:::i rn oomoom
I
SHIH)
c:J
l••TE•I
Now run the program in the same way you did before. It is "JOLLY AWFUL" to loose a
program line, isn' t
~t?
And since line loss can lead to some very subtle errors, you should exercise
c-0ution in writing your programs.
E. PROGRAM-LINE REVIEW keys
"But"', you might ask yourself, "How can I remember what lines I have entered?". Fear not
intrepid programm.er' This need to review has been anticipated and provided for with the CO
(Up Arrow) and CD (Down Arrow) keys. You may think of these as the Program·line Review
keys. By pressing the appropriate key (in PR Ogram mode), one may "move" up or down through
the lines of the current program (a process known appropriately as "scrolling").
Switch to the PROgram mode and use the Down Arrow key to review the lines of our program
in ascending order. Now use the Up Arrow key to move back to the top of the program {line 10).
Note that if either Arrow key is held down, successive lines will be displayed automatically.
(Unfortunately, Uiis feature is not easily seen with a two li ne program).
Once you have reached a given line usi ng the Program·line Review keys, you mllly then proceed
to edit that line using the Right o r Left Arrow keys. You will be delighted {relieved?) to discover
that the operation of these keys in the PROgram mode is identical to their operation in the RUN
mode (sec Chapter 2). The DELete and INSert fuonctions are also available fo r use in statement
editing, and are invoked in the same manner as before.
NOTE: That after any changes are made to a pro gram line. you must press ENTER in order to
affect those changes. DO NOT use the Up or Down Arrow keys to move on to the next adjacent
line without pressing
l t:•TE•I
or any editing you may have performed w ill be lost.
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