How to write a text input routine in Commodore BASIC

In this screencast I’ll show you how to write your own INPUT routine in Commodore BASIC. This comes in handy when you want to reject certain keys from being used when asking users for keyboard input. In my example I’m going to allow all alpha characters (A-Z), as well as SPACE, RETURN and the DELETE key.

Here’s the code:

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5 print 10 w$="" 20 print "(greater than)_"; 30 get a$:if a$="" then 30 40 a=asc(a$) 50 if a=13 then 200:rem return 60 if a=32 then 110:rem space 70 if a=20 then 300:rem backspace 100 if a<65 or a>90 then 30 110 print chr$(20);a$;"D"; 115 w$=w$+a$ 120 goto 30 200 rem handle return 210 print chr$(20) 215 if w$="" then print:print"you typed nothing!":end 220 print:print"you typed:":print w$ 230 end 300 rem handle backspace 305 if len(w$)=0 then 30 310 print chr$(20);chr$(20);"D"; 320 w$=left$(w$,len(w$)-1) 330 goto 30

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input.bas

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