puppybasic intro ch. 09 - working with binary files

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working with binary files                                        
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                  an intro to puppybasic                                 
                                                                         
                  chapter 9: working with binary files                   
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
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working with binary files                                        
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it might be fun at this point to learn how to save and load some data in 
a file, but this will be much more useful when you've learned about      
decision making and loops. in the meantime, here is how to work with     
binary files:                                                            
                                                                         
first of all, be sure to use this statement at the beginning of your     
program:                                                                 
DIM bt AS STRING * 1                                                     
                                                                         
so that you have a one byte string to work with. you can make longer     
strings, but this one will work for any purpose.                         
                                                                         
                                                                         
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always open the file :)                                                  
                                                                         
OPEN "filename.txt" FOR BINARY AS #1                                     
                                                                         
if you are only going to read the file, you dont strictly need the bt    
variable, and therefore don't need to DIM at the start of your program.  
just INPUT a byte:                                                       
                                                                         
b$=INPUT$(1, #1)                                                         
                                                                         
and that's all there is to that. yes, it IS similar to keyboard input.   
                                                                         
                                                                         
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do it again to read the next byte. usually, you'll probably want to use  
this method instead:                                                     
                                                                         
GET #1, q, bt                                                            
with q being the byte of the file you want to read... if q is 57, then   
it will read the 57th byte of the file.                                  
                                                                         
to write, use:                                                           
PUT #1, q, bt                                                            
where b is a string that's only one byte (or letter) long. it's pretty   
much the same idea. some useful functions for working with files are:    
                                                                         
                                                                         
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q = FREEFILE                                                             
                                                                         
sets q to the number of the next filenumber that's free... if you've     
opened a file as #1, and a second file, as #2, then FREEFILE will equal  
3.                                                                       
                                                                         
LOC(n)                                                                   
                                                                         
is the byte you're set to read or write at. if you've used INPUT$(1, #1) 
                                                                         
50 times already, LOC(1) will be 51.                                     
                                                                         
                                                                         
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LOF(n)                                                                   
                                                                         
is worth remembering, LOF(n) is equal to the length of file #n, if you   
open a file as #1 and the LOF(1) is 0, that file is empty.               
                                                                         
always close the file when you're done working with it:                  
                                                                         
CLOSE #1                                                                 
                                                                         
if you are only working with one file, or if you don't have any other    
files that you need to leave open, using close with no file numbers:     
                                                                         
                                                                         
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CLOSE                                                                    
                                                                         
will close all files.                                                    
                                                                         
                                                                         
                         -= end of chapter 9 =-                          
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
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an intro to puppybasic                                       (chapter 9) 
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