Initial data commit

Task/Queue-Usage/BBC-BASIC/queue-usage.basic

@@ -0,0 +1,31 @@
+      FIFOSIZE = 1000
+
+      FOR n = 3 TO 5
+        PRINT "Push ";n : PROCenqueue(n)
+      NEXT
+      PRINT "Pop " ; FNdequeue
+      PRINT "Push 6" : PROCenqueue(6)
+      REPEAT
+        PRINT "Pop " ; FNdequeue
+      UNTIL FNisempty
+      PRINT "Pop " ; FNdequeue
+      END
+
+      DEF PROCenqueue(n) : LOCAL f%
+      DEF FNdequeue : LOCAL f% : f% = 1
+      DEF FNisempty : LOCAL f% : f% = 2
+      PRIVATE fifo(), rptr%, wptr%
+      DIM fifo(FIFOSIZE-1)
+      CASE f% OF
+        WHEN 0:
+          wptr% = (wptr% + 1) MOD FIFOSIZE
+          IF rptr% = wptr% ERROR 100, "Error: queue overflowed"
+          fifo(wptr%) = n
+        WHEN 1:
+          IF rptr% = wptr% ERROR 101, "Error: queue empty"
+          rptr% = (rptr% + 1) MOD FIFOSIZE
+          = fifo(rptr%)
+        WHEN 2:
+          = (rptr% = wptr%)
+      ENDCASE
+      ENDPROC