puppybasic intro ch. 03 - variables

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regards to puppybasic.

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variables                                                                
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                  an intro to puppybasic                                 
                                                                         
                  chapter 3: variables                                   
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
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variables are the easiest way to store data in memory; of course, this   
memory is cleared when the program ends or the machine is turned off,    
but variables are useful when you want data in one part of your program  
to be available to another line in the program.                          
                                                                         
there are two main types of variables: string and numeric.               
                                                                         
string variable names start with a letter and are made of letters and    
numbers.                                                                 
                                                                         
                                                                         
                                                                         
                                                                         
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here is an example of a string variable at work:                         
                                                                         
q$="hello, world!"  ____________________________________________________ 
PRINT q$            _hello, world!______________________________________ 
PRINT q$            _hello, world!______________________________________ 
PRINT q$            _hello, world!______________________________________ 
PRINT q$            _hello, world!______________________________________ 
                    ____________________________________________________ 
                                                                         
this prints the contents of the string variable q$ 4 times.              
                                                                         
                                                                         
                                                                         
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strings, like those used by the PRINT statement, start and end with a    
double quote "like this." you cannot enter a string containing a double  
quote:                                                                   
"like "this example" does,"                                              
                                                                         
later on you'll learn a way around this using the CHR$ function.         
                                                                         
string variables almost always end in a dollar sign, while on the other  
hand, numeric variables often end without in any special symbol, even    
though there are other suffixes for specific types (which you usually    
wont need... but you may want them.)                                     
                                                                         
                                                                         
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all variables may be named with one or more letters, must start with a   
letter, and may include numbers (q2$ or q2 for example) after that.      
also, do not give a variable the same name as a statement or function    
(like "CLS") if you want your program to work.                           
                                                                         
it's worth showing that you can print a mix of strings and numbers, like 
in the example on the next page...                                       
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
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                          ______________________________________________ 
n=50                      __7 hello, world! 50 times.___________________ 
PRINT 7; q$; n; "times."  ______________________________________________ 
                                                                         
...and you can combine two strings into one with the + sign like this:   
                                                                         
q$="hello"                                                               
q$="oh, "+q$+" there..."                                                 
                                                                         
now the string "oh, hello there..." is stored in the variable q$.        
combining strings this way, with or without variables, is called         
"concatonization" and does not work with numeric variables.              
                                                                         
                                                                         
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there are a couple more things you might want to know before moving on:  
it is often preferable (in the interest of time and effort) to type a    
question mark:  ? "hello."                                               
                                                                         
instead of typing out PRINT, puppybasic will (along with many other          
interpreters and compilers) change it to PRINT for you. it won't stop    
you from using a question mark where you actually want one:              
                                                                         
? "do you want to quit?"                                                 
will change to:                                                          
PRINT "do you want to quit?"                                             
                                                                         
                                                                         
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also, instead of giving each statement its own line, you may often find  
you prefer to combine lines of code using a colon :                      
                                                                         
CLS: PRINT "to whom it may concern"; : PRINT ":"                         
                                                                         
will clear the screen and PRINT the following:                           
                                                                         
________________________________________________________________________ 
_to whom it may concern:________________________________________________ 
________________________________________________________________________ 
________________________________________________________________________ 
                                                                         
                                                                         
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COLOR 10: PRINT "dear abby"; : PRINT ","                                 
                                                                         
will print:  ___________________________________________________________ 
             _dear abby,________________________________________________ 
             ___________________________________________________________ 
                                                                         
congratulations! if you have not already, you can now write your first   
puppybasic program. you will be able to do much more after reading the  
next section.                                                                 
                                                                         
                         -= end of chapter 3 =-                          
                                                                         
                                                                         
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an intro to puppybasic                                       (chapter 3) 
this content is public domain.                          
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