puppybasic intro ch. 07 - keyboard and data lines

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keyboard and data lines                                                  
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                  an intro to puppybasic                                 
                                                                         
                  chapter 7: keyboard and data lines                     
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
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keyboard and data lines                                                  
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let's get DATA statements out of the way, since i find them irritating,  
although you'll want to know how they work when you see them in someone  
else's code.                                                             
                                                                         
DATA statements (though as i said, i don't like them) are easy enough to 
use.                                                                     
                                                                         
anywhere in the main module of the program (don't even worry about what  
that is) put the statement DATA followed by the strings or numbers you   
want read, separated by commas:                                          
                                                                         
                                                                         
                                                                         
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keyboard and data lines                                                  
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DATA ugh., data, statements-, that takes, me back.                       
                                                                         
READ q$: ? q$;  ________________________________________________________ 
READ q$: ? q$;  _ugh.datastatements-that takesme back.__________________ 
READ q$: ? q$;  ________________________________________________________ 
READ q$: ? q$;  ________________________________________________________ 
READ q$: ? q$;                                                           
there are better ways, but this works. if you use DATA statements, you   
may find that you want to put something unique as the last string or     
number so that your routine can "know" when it's done reading, but       
you'll need loops and decision making (covered later) to pull it off.    
                                                                         
                                                                         
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keyboard and data lines                                                  
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if you READ a number of times greater than your number of data entries,  
you get an error and your program stops. to avoid this, don't read a     
greater number of times than your number of entries. (heh.) along with a 
unique last entry, you can reread from the beginning of your data        
statements. (puppybasic looks at all of them together, from the 
beginning of your program to the end, as one long data statement) by 
putting an old fashioned line number (like 20) before your first data 
statement, which then allows you to use the command:                                      
                                                                         
RESTORE 20                                                               
                                                                         
                                                                         

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keyboard and data lines                                                  
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whenever you want to reread. you can also move to different places (in   
your single virtually continuous data line) but putting line numbers     
between DATA statements:                                                 
                                                                         
RESTORE 70: READ b$: PRINT b$ + ",";: READ b$: PRINT b$; "."             
                                                                         
50                      ________________________________________________ 
DATA 5,6,7,8,9          _ok,that's enough.______________________________ 
70                      ________________________________________________ 
DATA ok, that's enough  ________________________________________________ 
                        ________________________________________________ 
                                                                         
                                                                         
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keyboard and data lines                                                  
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i think the most versatile way to get keyboard input is with the INKEY$  
function, but it doesn't wait for input: it just says "hey! keyboard,    
what's happenin'?" and unless a key has been pressed already the         
keyboard just says "..." and INKEY$ returns an empty, 0-length string... 
not even a space, just the nothing between two quotes, side by side: "". 
                                                                         
there's nothing wrong with this, it's just that INKEY$ only works in a   
loop, so i'll demonstrate INKEY$ after showing how loops work. in the    
meantime, INPUT$(n) is similar, and not too shabby. i'll show you that   
momentarily. in order to appreciate the simple beauty of INPUT$(n) you   
have to see the alternatives:                                            
                                                                         
                                                                         
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keyboard and data lines                                                  
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INPUT "", q$                                                             
                                                                         
you can put stuff in the quotes, and then it's like a PRINT statement,   
but i prefer using PRINT to print and INPUT for input. one advantage of  
separating the two is that you can put the instructions and the visible  
end of the keyboard input on separate lines or different locations on    
the screen. i'm really trying to set a good example here by showing      
INPUT used with a comma - you could use a semicolon:  INPUT ""; q$       
                                                                         
but INPUT "please type your name - "; q$  ______________________________ 
will show up on the screen like this:     _please type your name - ?____ 
                                                                         
                                                                         
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keyboard and data lines                                                  
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because as we all know the ONLY way to get information from the user is  
in the form of a full sentence followed by a question mark :|            
                                                                         
ah well. this is why using a comma is better.                            
                                                                         
of course, i don't actually recommend using the INPUT statement, ever.   
LINE INPUT is used the same way you just learned (see? that wasn't in    
vain) but is more reliable. i'll explain:                                
                                                                         
say for instance, you used this code:                                    
                                                                         
                                                                         
                                                                         
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keyboard and data lines                                                  
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INPUT "enter your name - ", n$     _____________________________________ 
and say for instance, he entered:  _enter your name - smith, john q.____ 
                                   _____________________________________ 
then he would see this message:    _REDO FROM START?____________________ 
                                   _____________________________________ 
great! what?                       _____________________________________ 
                                                                         
it's because he typed a comma. the INPUT statement is designed so that   
you can get more than one piece of data from the same prompt, separated  
by commas, like this:                                                    
                                                                         
                                                                         
                                                                         
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keyboard and data lines                                                  
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INPUT "please enter three numbers, put commas between the first          
and second, and also between the second and third, and don't forget      
them, and don't put too many, or my input routine will yell at you.      
thanks. ", a, b, c                                                       
                                                                         
assuming your plucky user gets it exactly right, the clever INPUT        
statement will save an extra line of code.                               
                                                                         
                                                                         
Bad Design!                                                              
                                                                         
                                                                         
                                                                         
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so i never use the INPUT statement. ever. instead i use this when i want 
a no fuss, two line method of getting keyboard input (there are better   
ways using INKEY$, remember?)                                            
                                                                         
PRINT "please enter your name. as long as your name has less than 250    
characters and doesn't contain carriage returns, we shouldn't have any   
problems:": ?: line input n$                                             
                                                                         
all this is okay, for typing in a line of data and hitting enter. if you 
have a menu on the other hand:                                           
                                                                         
                                                                         
                                                                         
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keyboard and data lines                                                  
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1. do something                                                          
                                                                         
2. do something else                                                     
                                                                         
3. do something entirely different                                       
                                                                         
4. exit                                                                  
                                                                         
then the following prompt might seem reasonable:                         
                                                                         
? "please enter your selection - ";: LINE INPUT q$                       
                                                                         
                                                                         
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keyboard and data lines                                                  
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but i think this is better:                                              
                                                                         
1. do something                                                          
                                                                         
2. do something else                                                     
                                                                         
3. do something entirely different                                       
                                                                         
? "select an option (1-3) or hit [esc] to exit :)": q$=INPUT$(1)         
                                                                         
                                                                         
                                                                         
                                                                         
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now q$ will be exactly one byte long and be a 1, or 2, or 3, or esc      
(esc is ascii 27.) it might be something else, but you can check to see  
if it's one of the acceptable options, and repeat until it's a key you   
are looking for. yeah, i'll get to looping.                              
                                                                         
you can also change the "1" in INPUT$(1) to another number, 5 for        
instance, if you want exactly 5 keys input to the program. this too, is  
bad design because the person can't see what they're typing, and can't   
backspace if they hit a wrong key.                                       
                                                                         
                                                                         
                                                                         
                                                                         
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usually, i'll use INKEY$. in a loop, INKEY$ can act just like INPUT$(n)  
if you want it to and can detect arrow and function keys as well.        
                                                                         
                                                                         
                         -= end of chapter 7 =-                          
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
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an intro to puppybasic                                       (chapter 7) 
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