``` 10 sum=0 20 FOR i=28672 TO 28758 30 READ n 40 POKE i,n : sum+=n 50 NEXT i 60 IF sum <> 9387 THEN PRINT "Error in DATA" : STOP 70 x= USR 28672 80 IF INT ( PEEK (28757)/2)= PEEK (28757)/2 THEN PRINT "Disk Error ";PEEK (28758): STOP 90 IF x=1 THEN PRINT "No file found": STOP 100 FOR i=0 TO x-2 110 FOR j=0 TO 10 120 PRINT CHR$ ( PEEK (32781+i*13+j)); 130 NEXT j 140 PRINT 150 NEXT i 160 DATA 243,237,115,0,144,1, 253,127,58,92,91,203,167,2 46,7,50,92,91,237,121,49,2 55,159,251 170 DATA 33,0,128,17,1,128,1, 0,4,54,0,237,176,6,64,14,1 ,17,0,128,33,81,112,205,30 ,1,245,225,34,85,112,72,6, 0 180 DATA 243,197,1,253,127,58, 92,91,203,231,230,248,50,9 2,91,237,121,193,237,123,0 , 144,201 190 DATA 42,46,42,255,0,0 ``` The addresses picked for the above code and its data areas are completely arbitrary. However, it is a good idea to keep things in the central **32K** wherever possible so as not to run into the pitfall of accidentally switching out a vital variable or piece of code. If interrupts are to be enabled (as is the case in the above example), it is imperative that the system is kept up to date about the latest ROM switch. This means, that the user must make the BANK678 system variable reflect the last value output to the port at **1FFDh**. As shown by the above example, the general technique is to take a copy of the variable in **A**, set/reset the relevant bits, update the system variable then make the switch with an **OUT** instruction. Interrupts must be disabled while the system variable does not reflect the cur-