Why is my program hit & miss on the output?

[Cobalt]

So roughly 33% of the time this program fails to display any output. its pretty straight forward so I'm at a loss of whats going on. Could I be encountering some kind of race condition somewhere? Given it doesn't happen every time, it may not be easily diagnose-able.
The CONST WALL will need to be changed back to chr$(178)[from the ascii chart in the IDE] once you copy it in the IDE. Like many other places you can not paste the true ASCII(extended) character here. (well at least it wont let me)

Code: QB64: [Select]

1. DIM SHARED Layer(10) AS LONG
2. DIM SHARED temp AS _MEM
3. CONST Wall = "²" 'CHR$(178)
4.  
5. SCREEN _NEWIMAGE(100, 40, 0)
6. Layer(0) = _DISPLAY
7. Layer(1) = _COPYIMAGE(_DISPLAY)
8. temp = _MEMIMAGE(Layer(1))
9. _DELAY .1
10. _SCREENMOVE 5, 5
11. FOR i%% = 0 TO 12
12.  ClearLayer Layer(1)
13.  SELECT CASE i%%
14.   CASE 0
15.    Room00
16.   CASE 1
17.    Room01
18.   CASE 2
19.    Room02
20.   CASE 3
21.    Room03
22.   CASE 4
23.    Room04
24.   CASE 5
25.    Room05
26.   CASE 6
27.    Room06
28.   CASE 7
29.    Room07
30.   CASE 8
31.    Room08
32.   CASE 9
33.    Room09
34.   CASE 10
35.    Room10
36.   CASE 11
37.    Room11
38.   CASE 12
39.    Room12
40.   CASE 13
41.    Room12
42.   CASE 14
43.    Room03
44.   CASE 15
45.    Room03
46.  END SELECT
47.  
48.  PCOPY Layer(1), Layer(0)
49.  LOCATE 35, 1: PRINT "Room"; i%%
50.  _DELAY 1.25
51. NEXT i%%
52. SLEEP
53.  
54. SUB ClearLayer (L&)
55.  old& = _DEST
56.  _DEST L&
57.  CLS ' ,0
58.  _DEST old&
59. END SUB
60.  
61. SUB ClearLayerTrans (L&)
62.  old& = _DEST
63.  _DEST L&
64.  CLS , 0
65.  _DEST old&
66. END SUB
67.  
68. SUB Room00
69.  'solid room
70.  FOR i%% = 0 TO 70
71.   _MEMPUT temp, temp.OFFSET + i%% * 2, 178 AS _UNSIGNED _BYTE
72.   _MEMPUT temp, temp.OFFSET + 200 * 31 + i%% * 2, 178 AS _UNSIGNED _BYTE
73.  NEXT i%%
74.  FOR i%% = 1 TO 30
75.   _MEMPUT temp, temp.OFFSET + 140 + i%% * 200, 178 AS _UNSIGNED _BYTE
76.   _MEMPUT temp, temp.OFFSET + i%% * 200, 178 AS _UNSIGNED _BYTE
77.  NEXT i%%
78. END SUB
79.  
80. SUB Room01
81.  'South Exit room
82.  FOR i%% = 0 TO 70
83.   _MEMPUT temp, temp.OFFSET + i%% * 2, 178 AS _UNSIGNED _BYTE
84.  NEXT i%%
85.  FOR i%% = 0 TO 30
86.   _MEMPUT temp, temp.OFFSET + 200 * 31 + i%% * 2, 178 AS _UNSIGNED _BYTE
87.   _MEMPUT temp, temp.OFFSET + 200 * 31 + 140 - i%% * 2, 178 AS _UNSIGNED _BYTE
88.  NEXT i%%
89.  FOR i%% = 1 TO 30
90.   _MEMPUT temp, temp.OFFSET + 140 + i%% * 200, 178 AS _UNSIGNED _BYTE
91.   _MEMPUT temp, temp.OFFSET + i%% * 200, 178 AS _UNSIGNED _BYTE
92.  NEXT i%%
93. END SUB
94.  
95. SUB Room02
96.  'North Exit room
97.  FOR i%% = 0 TO 70
98.   _MEMPUT temp, temp.OFFSET + 200 * 31 + i%% * 2, 178 AS _UNSIGNED _BYTE
99.  NEXT i%%
100.  FOR i%% = 0 TO 30
101.   _MEMPUT temp, temp.OFFSET + i%% * 2, 178 AS _UNSIGNED _BYTE
102.   _MEMPUT temp, temp.OFFSET + 140 - i%% * 2, 178 AS _UNSIGNED _BYTE
103.  NEXT i%%
104.  FOR i%% = 1 TO 30
105.   _MEMPUT temp, temp.OFFSET + 140 + i%% * 200, 178 AS _UNSIGNED _BYTE
106.   _MEMPUT temp, temp.OFFSET + i%% * 200, 178 AS _UNSIGNED _BYTE
107.  NEXT i%%
108. END SUB
109.  
110. SUB Room03
111.  'West Exit room
112.  FOR i%% = 0 TO 70
113.   _MEMPUT temp, temp.OFFSET + i%% * 2, 178 AS _UNSIGNED _BYTE
114.   _MEMPUT temp, temp.OFFSET + 200 * 31 + i%% * 2, 178 AS _UNSIGNED _BYTE
115.  NEXT i%%
116.  FOR i%% = 1 TO 12
117.   _MEMPUT temp, temp.OFFSET + i%% * 200, 178 AS _UNSIGNED _BYTE
118.   _MEMPUT temp, temp.OFFSET + 31 * 200 - i%% * 200, 178 AS _UNSIGNED _BYTE
119.  NEXT i%%
120.  FOR i%% = 1 TO 30
121.   _MEMPUT temp, temp.OFFSET + 140 + i%% * 200, 178 AS _UNSIGNED _BYTE
122.  NEXT i%%
123. END SUB
124.  
125. SUB Room04
126.  'East Exit room
127.  FOR i%% = 0 TO 70
128.   _MEMPUT temp, temp.OFFSET + i%% * 2, 178 AS _UNSIGNED _BYTE
129.   _MEMPUT temp, temp.OFFSET + 200 * 31 + i%% * 2, 178 AS _UNSIGNED _BYTE
130.  NEXT i%%
131.  FOR i%% = 1 TO 30
132.   _MEMPUT temp, temp.OFFSET + i%% * 200, 178 AS _UNSIGNED _BYTE
133.  NEXT i%%
134.  FOR i%% = 1 TO 12
135.   _MEMPUT temp, temp.OFFSET + 140 + i%% * 200, 178 AS _UNSIGNED _BYTE
136.   _MEMPUT temp, temp.OFFSET + 31 * 200 + 140 - (i%% * 200), 178 AS _UNSIGNED _BYTE
137.  NEXT i%%
138. END SUB
139.  
140. SUB Room05
141.  'North + South Exit room
142.  FOR i%% = 0 TO 30
143.   _MEMPUT temp, temp.OFFSET + 200 * 31 + i%% * 2, 178 AS _UNSIGNED _BYTE
144.   _MEMPUT temp, temp.OFFSET + 200 * 31 + 140 - i%% * 2, 178 AS _UNSIGNED _BYTE
145.  NEXT i%%
146.  FOR i%% = 1 TO 30
147.   _MEMPUT temp, temp.OFFSET + 140 + i%% * 200, 178 AS _UNSIGNED _BYTE
148.   _MEMPUT temp, temp.OFFSET + i%% * 200, 178 AS _UNSIGNED _BYTE
149.  NEXT i%%
150.  
151.  FOR i%% = 0 TO 30
152.   _MEMPUT temp, temp.OFFSET + i%% * 2, 178 AS _UNSIGNED _BYTE
153.   _MEMPUT temp, temp.OFFSET + 140 - i%% * 2, 178 AS _UNSIGNED _BYTE
154.  NEXT i%%
155.  FOR i%% = 1 TO 30
156.   _MEMPUT temp, temp.OFFSET + 140 + i%% * 200, 178 AS _UNSIGNED _BYTE
157.   _MEMPUT temp, temp.OFFSET + i%% * 200, 178 AS _UNSIGNED _BYTE
158.  NEXT i%%
159. END SUB
160.  
161. SUB Room06
162.  'Ease + West Exit room
163.  FOR i%% = 0 TO 70
164.   _MEMPUT temp, temp.OFFSET + i%% * 2, 178 AS _UNSIGNED _BYTE
165.   _MEMPUT temp, temp.OFFSET + 200 * 31 + i%% * 2, 178 AS _UNSIGNED _BYTE
166.  NEXT i%%
167.  FOR i%% = 1 TO 12
168.   _MEMPUT temp, temp.OFFSET + i%% * 200, 178 AS _UNSIGNED _BYTE
169.   _MEMPUT temp, temp.OFFSET + 31 * 200 - i%% * 200, 178 AS _UNSIGNED _BYTE
170.  NEXT i%%
171.  FOR i%% = 1 TO 12
172.   _MEMPUT temp, temp.OFFSET + 140 + i%% * 200, 178 AS _UNSIGNED _BYTE
173.   _MEMPUT temp, temp.OFFSET + 31 * 200 + 140 - (i%% * 200), 178 AS _UNSIGNED _BYTE
174.  NEXT i%%
175. END SUB
176.  
177. SUB Room07
178.  'North + South + West Exit room
179.  FOR i%% = 0 TO 30
180.   _MEMPUT temp, temp.OFFSET + 200 * 31 + i%% * 2, 178 AS _UNSIGNED _BYTE
181.   _MEMPUT temp, temp.OFFSET + 200 * 31 + 140 - i%% * 2, 178 AS _UNSIGNED _BYTE
182.  NEXT i%%
183.  FOR i%% = 1 TO 12
184.   _MEMPUT temp, temp.OFFSET + i%% * 200, 178 AS _UNSIGNED _BYTE
185.   _MEMPUT temp, temp.OFFSET + 31 * 200 - i%% * 200, 178 AS _UNSIGNED _BYTE
186.  NEXT i%%
187.  
188.  FOR i%% = 0 TO 30
189.   _MEMPUT temp, temp.OFFSET + i%% * 2, 178 AS _UNSIGNED _BYTE
190.   _MEMPUT temp, temp.OFFSET + 140 - i%% * 2, 178 AS _UNSIGNED _BYTE
191.  NEXT i%%
192.  FOR i%% = 1 TO 30
193.   _MEMPUT temp, temp.OFFSET + 140 + i%% * 200, 178 AS _UNSIGNED _BYTE
194.  NEXT i%%
195. END SUB
196.  
197. SUB Room08
198.  'North + South + East Exit room
199.  FOR i%% = 0 TO 30
200.   _MEMPUT temp, temp.OFFSET + 200 * 31 + i%% * 2, 178 AS _UNSIGNED _BYTE
201.   _MEMPUT temp, temp.OFFSET + 200 * 31 + 140 - i%% * 2, 178 AS _UNSIGNED _BYTE
202.  NEXT i%%
203.  FOR i%% = 1 TO 30
204.   _MEMPUT temp, temp.OFFSET + i%% * 200, 178 AS _UNSIGNED _BYTE
205.  NEXT i%%
206.  
207.  FOR i%% = 0 TO 30
208.   _MEMPUT temp, temp.OFFSET + i%% * 2, 178 AS _UNSIGNED _BYTE
209.   _MEMPUT temp, temp.OFFSET + 140 - i%% * 2, 178 AS _UNSIGNED _BYTE
210.  NEXT i%%
211.  FOR i%% = 1 TO 12
212.   _MEMPUT temp, temp.OFFSET + 140 + i%% * 200, 178 AS _UNSIGNED _BYTE
213.   _MEMPUT temp, temp.OFFSET + 31 * 200 + 140 - (i%% * 200), 178 AS _UNSIGNED _BYTE
214.  NEXT i%%
215. END SUB
216.  
217. SUB Room09
218.  'North + West exit room
219.  FOR i%% = 0 TO 70
220.   _MEMPUT temp, temp.OFFSET + 200 * 31 + i%% * 2, 178 AS _UNSIGNED _BYTE
221.  NEXT i%%
222.  FOR i%% = 1 TO 30
223.   _MEMPUT temp, temp.OFFSET + 140 + i%% * 200, 178 AS _UNSIGNED _BYTE
224.  NEXT i%%
225.  FOR i%% = 1 TO 12
226.   _MEMPUT temp, temp.OFFSET + i%% * 200, 178 AS _UNSIGNED _BYTE
227.   _MEMPUT temp, temp.OFFSET + 31 * 200 - i%% * 200, 178 AS _UNSIGNED _BYTE
228.  NEXT i%%
229. END SUB
230.  
231. SUB Room10
232.  'North + East exit room
233.  FOR i%% = 0 TO 70
234.   _MEMPUT temp, temp.OFFSET + 200 * 31 + i%% * 2, 178 AS _UNSIGNED _BYTE
235.  NEXT i%%
236.  FOR i%% = 1 TO 30
237.   _MEMPUT temp, temp.OFFSET + i%% * 200, 178 AS _UNSIGNED _BYTE
238.  NEXT i%%
239.  FOR i%% = 1 TO 12
240.   _MEMPUT temp, temp.OFFSET + 140 + i%% * 200, 178 AS _UNSIGNED _BYTE
241.   _MEMPUT temp, temp.OFFSET + 31 * 200 + 140 - (i%% * 200), 178 AS _UNSIGNED _BYTE
242.  NEXT i%%
243. END SUB
244.  
245. SUB Room11
246.  'South + West exit room
247.  FOR i%% = 0 TO 70
248.   _MEMPUT temp, temp.OFFSET + i%% * 2, 178 AS _UNSIGNED _BYTE
249.  NEXT i%%
250.  FOR i%% = 1 TO 30
251.   _MEMPUT temp, temp.OFFSET + 140 + i%% * 200, 178 AS _UNSIGNED _BYTE
252.  NEXT i%%
253.  FOR i%% = 1 TO 12
254.   _MEMPUT temp, temp.OFFSET + i%% * 200, 178 AS _UNSIGNED _BYTE
255.   _MEMPUT temp, temp.OFFSET + 31 * 200 - i%% * 200, 178 AS _UNSIGNED _BYTE
256.  NEXT i%%
257. END SUB
258.  
259. SUB Room12
260.  'South + East exit room
261.  FOR i%% = 0 TO 70
262.   _MEMPUT temp, temp.OFFSET + i%% * 2, 178 AS _UNSIGNED _BYTE
263.  NEXT i%%
264.  FOR i%% = 1 TO 30
265.   _MEMPUT temp, temp.OFFSET + i%% * 200, 178 AS _UNSIGNED _BYTE
266.  NEXT i%%
267.  FOR i%% = 1 TO 12
268.   _MEMPUT temp, temp.OFFSET + 140 + i%% * 200, 178 AS _UNSIGNED _BYTE
269.   _MEMPUT temp, temp.OFFSET + 31 * 200 + 140 - (i%% * 200), 178 AS _UNSIGNED _BYTE
270.  NEXT i%%
271. END SUB
272.  

[FellippeHeitor]

CONST doesn't handle string functions, but that didn't trigger an error until v1.5 - the IDE will properly warn you about that in the latest dev build.

Make your CONST a SHARED STRING instead and all the rest will remain untouched (and work).

[FellippeHeitor]

Notice I'm just pointing out the issue with CONST - I didn't run your code, can't offer advice right now.