Sharp PC-1500 Instruction Manual page 98

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G. DEBUGGING
No matter hovv carefu l you a rc , eventually you will creat e a program which does not do quite
what you expect it to. In order to isolate the problem, SHARP's designers have provided a special
method of executing programs known as the "Trace" mode . In t he Trace mode , th e PC· 1500 will
display the line-number o f eac h program line and \\lill hal t a ft er the execution of that line. This
allov1s you to follow (or t race) the sequence of ins.t ructions as they ar e actually pe·rformcd. Wh en
the program pauses afte r the execution of a line . y ou may inspect or
~l ter
the val ues of vadables.
The form of th e instructio n for initiating the- T race mode is simply: TRON. The TRON
instruction may be issued as a command {in RUN mode) or it may be embedded .. as a statement,
w ithin a p rogram . Used as a command, TRON informs SHARP th at t racing is required during
the ex· e cution of a ll subsequent programs. The programs to be t raced are then started in a n ormal
manner, wi th a GOTO or RUN command .
If TRON is used as a statement, it will initiate the Trace mode only when t he line containing
it is executed . If, fo r some reason, that line is
never
reached, the Trace mode \viii remain inactive.
Once in itiated, t he Trace mode of operation remains in effect until canceled by a TROFF
inst ruction. The TRO FF inst ruction may also be issued as ei ther a command or a st atement.
The Trace mode ca n also be canceled by the key sequence:
As an example of ... 1sing the Trace mode, enter the follo,ning program to com p u te th e length
o f the hypotenuse of a triangle given the length of the sides:
Program Listing:
10 IN PUT
A.
B
2()
A = A*A: B = B*B
30 H = y(A + B)
40 PR INT "HYPOTENUSE =
'"
H
In RUN mode, issue the T RON command, followed by the R UN command. Not ice t hat the
INPUT command operates in the usual manne r by display ing a question mark fo r each inpu t
value required. As soon as you have en tered t wo values, the line number of th e INPUT statement
appears :
RUN
· 1
1 0
By pressing the
CD
(Up Arrow) key a nd holding it. you may review the entire lin e :
RU N
;-i
I
1 0 IN PUT A, B
To continue the p :rogram, press the
IT)
(OO\vn A rrow) key o nce. This causes thie 1)e>:.t line to be
execu ted and its l ine number to be d isplayed. Again, you may review the tine with the (Up
Arro\v) key. You may a lso ch eck the c ontents of a ny variable by t yping its name and pressing
!1!HJl!Jt) :
96
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