Sharp PC-1500 - Page 38

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As an exam pl e of a progr am which fai ls to do t hi s, ent er the following:
Program Lis ting:
10 A - 0
20 INPUT A
30 PRINT A*P I
Ke ys tr okes:
r11 ooru r= 1 00l •• n• I
W(J)JOJ oom uo mm, •• , •• ,
rnrnmoocoao rn (A] mm1 ..... ,
Now im agi ne t.he user as he runs the program ... The first thing th at appears on the display is
n quns tion mark. The kn owl cd go ab le u ser will realize that s om e do to is requi re d but he will h~vc no
id ea what th at d.ata sh ould be. Suppose he takes a wild guess. and luck il y, enters a number.
Suddenly, a long and comp li cated number app ears. What does it mean? He pr ess es ENTER to
cont inue, but t he pr ogram ends. F ro m his viewpoin t, th e whole experience h a~ been a waste of
time. Why? Because of poor programming.
One soluti on to this problem is to u se PRINT or PAUSE statements to h elp the user along.
With this idea \\'e -c an re- i,,
1
1r itc our pro g ram as fo ll ows :
Pr\l9ram Li $ tin9 :
10 A = 0
20 PAU SE "E NTER ANY NUMB ER"
30 IN PUT A
40 AP = A * Pl
50 PRI NT A; " TIMES Pl = " ; AP
Keystrokes:
CD [ A J I= 1 OD l• HTl• I
moommrnocm1 .. .., 1 ~rn CtJITJ OD@m
00 CD ! sP >a l 00 OiJ 00 ru CB:! ' "" " I c:::::J !! • ., •I
CD CU [!] aJ ODCD CXJ !f., ca l
mm r.cJ 01 O=J m rn m rn , ,.. ,. .1
m rn C!J oo co CEJ com CED c:o 1•H• Fr 1 c:::i , .,. .«,
rr 1cn oom rn , .,.., ., m CDt •••c• IC: = J
@ o. ei!J ' """' 1 c:::i 1 SHIFT 1 moo m 1 .. TF. 1
This versi on is much mo re u se ful because it "pr o mpt s" (or provoke s} t.h e us er for in pu t and
because it identifi es the ou tpu t.
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