HELP / ANSWERS                         
                                                                
                        by Geoff Bridges                        
                                                                
                                                           
  If the E-Tracker player was loaded first, then the music was  
lost when the mouse driver was loaded and if the mouse code was 
loaded first then mouse control was lost when the music code was
loaded.                                                         
  Whats happening here is simply that both programs load their  
code into the same place, so the second one loaded overwrites   
the first one! The area selected for the code is the system heap
starting at memory location 16384.                              
  Space can be reserved in the heap for a code routine and the  
mouse driver program does this automaticaly, but the E-Tracker  
loader does not. Heap space can be reserved in machine code by  
calling the ROM routine at address 262 or by using the RESERVED 
function in MASTERBASIC. There is no command in SAM BASIC to    
reserve heap space but the system variable HEAPEND (SVAR 456)   
can be poked with the new heap end.                             
  Assuming that the code starts from 16384 (which is the case   
for the E-TRACKER code), the value to poke to SVAR 456 is 16384+
125(the code length). This can be poked before OR after the     
E-TRACKER code is loaded, but MUST be poked before the mouse    
driver code is loaded.                                          
  The modified "Int-music" listing is below. Note that the      
program has been RENUMbered and so the lines may not be the same
number as in the original.                                      
                                                                
   10 REM This is the E-TRACKER Int-music program modified to be
       used with a mouse driver installed                       
   20 IF DPEEK SVAR 456=16384                                   
   30 DPOKE SVAR 456,16509                                      
   40 LOAD "mdriver"CODE                                        
   50 END IF                                                    
   60 PRINT "PLEASE WAIT"                                       
   70 LET PAGE=11: LET ADR=16384                                
   80 DO                                                        
   90 READ A: EXIT IF A<0                                       
  100 POKE ADR,A: LET ADR=ADR+1                                 
  110 LOOP                                                      
  120 REM REPLACE 'MUSIC' BELOW WITH THE FILENAME OF YOUR COMPI 
      LED MUSIC                                                 
  130 LOAD "MUSIC"CODE 16384*(PAGE+1): POKE &5100+PAGE,32       
                                                                
  140 CLS : PRINT "TO START MUSIC : CALL 16384"'"TO STOP MUSIC  
      : CALL 16387"                                             
  150 CALL 16384: POKE SVAR 666,5                               
  160 PRINT "Mouse is now active"'"POKE SVAR 666,0 to clear mous
      e pointer"'"POKE SVAR 666,1 to 7 to enable pointer"       
  170 DATA 195,6,64,195,32,64,243,42,112,91                     
  180 DATA 34,34,64,33,52,64,34,112,91,62                       
  190 DATA PAGE,211,251,205,0,128,62,1,211,251                  
  200 DATA 251,201,243,33,0,0,34,112,91,62                      
  210 DATA PAGE,211,251,205,0,128,62,1,211,251                  
  220 DATA 251,201,203,89,40,3,195,73,0,197                     
  230 DATA 213,221,229,253,229,8,217,245,197,213                
  240 DATA 229,205,89,64,225,209,193,241,8,217                  
  250 DATA 253,225,221,225,209,193,195,73,0,219                 
  260 DATA 251,50,109,64,237,115,113,64,49,0                    
  270 DATA 192,62,PAGE,211,251,205,6,128,62,0                   
  280 DATA 211,251,49,0,0,201,-1                                
  310 DO                                                        
  320 IF BUTTON 1                                               
  330 IF YMOUSE>183 THEN CALL 16384                             
  340 IF YMOUSE>173 AND YMOUSE<183 THEN CALL 16387              
  345 PAUSE 10                                                  
  350 END IF                                                    
  360 LOOP                                                      
                                                                
    Lines 20 to 50 are the new additions. The IF....END IF      
sequence is used to avoid reloading the mouse driver if the     
program is stopped and then re-RUN.                             
                                                                
  Line 150 turns the music on and activates the mouse pointer.  
                                                                
  Lines 310 to 360 are a 'test' routine to show the use of the  
mouse and music combination.                                    
                                                                
  Pressing the left button with the pointer on the top line of  
text will turn the music on. Pressing the left button on the    
second line of text will stop the music.                        
                                                                
  The PAUSE in line 345 is to slow down the DO..LOOP to enable  
the mouse driver to update the position readings. In normal use 
there would be more program code to allow enough time for the   
mouse update.