The very last routine is a good place to start. It's the adventure shop.
First we clear the screen and print the title.
60200 HOME : PRINT "WELCOME TO THE ADVENTURE SHOP"
Next we ask the player what item they want to buy (they just press a key).
60210 PRINT "WHICH ITEM SHALT THOU BUY ";: GET Q$: IF Q$ = "Q" THEN PRINT : PRINT "BYE": FOR Z = 1 TO 1000: NEXT : TEXT : HOME : RETURN
If "Q" is pressed, we say BYE, pause, clear the screen again and return.
Next, given what was pressed, we work out the corresponding index Z into some array and price P.
We initially set Z to -1 so we know if we've fallen through the if statements without matching anything.
60215 Z = - 1
60220 IF Q$ = "F" THEN PRINT "FOOD":Z = 0:P = 1
60221 IF Q$ = "R" THEN PRINT "RAPIER":Z = 1:P = 8
60222 IF Q$ = "A" THEN PRINT "AXE":Z = 2:P = 5
60223 IF Q$ = "S" THEN PRINT "SHIELD":Z = 3:P = 6
60224 IF Q$ = "B" THEN PRINT "BOW":Z = 4:P = 3
60225 IF Q$ = "M" THEN PRINT "AMULET":Z = 5:P = 15
If Z is still -1, we did match anything so display and message and try again:
60226 IF Z = - 1 THEN PRINT Q$: PRINT "I'M SORRY WE DON'T HAVE THAT.": GOTO 60210
Next we check if the player's class allows them to have a rapier or bow. Class is stored in PT$ and M corresponds to a Mage.
60227 IF Q$ = "R" AND PT$ = "M" THEN PRINT "I'M SORRY MAGES": PRINT "CAN'T USE THAT!": GOTO 60210
60228 IF Q$ = "B" AND PT$ = "M" THEN PRINT "I'M SORRY MAGES": PRINT "CAN'T USE THAT!": GOTO 60210
Next we check if the player can afford the price P. C(5) seems to be the amount of gold the player has.
60230 IF C(5) - P < 0 THEN PRINT "M'LORD THOU CAN NOT AFFORD THAT ITEM.": GOTO 60210
PW seams to be an array of how many items of each type the player has. Normally buying an item increments its count by 1 but food is incremented by 10 so in that case we first increment it by 9 before the general case increments it by another one. We also subtract the price P from C(5).
60235 IF Z = 0 THEN PW(Z) = PW(Z) + 9
60236 PW(Z) = PW(Z) + 1:C(5) = C(5) - P
Finally, we update the display with the new counts:
60237 VTAB (10): HTAB (16): PRINT C(5);" "
60240 VTAB (5 + Z): HTAB (25 - LEN ( STR$ (PW(Z)))): PRINT PW(Z);: HTAB (1): VTAB (14): PRINT
and go back to asking if they want to buy anything else:
60250 GOTO 60210