Glitchoidz Report

The GLITCHOIDZ REPORT will pass on to our readers errors, problems, and other Glitchoid activities which have been discovered. We welcome your contributions to this column.

GOTO Lines

Some readers have asked about a line such as GOTO 450 when the program does not have a line 450. In the ZX80 this does not stop the program or confuse the computer. The ZX80 will search for the line and, failing to find it, go on to the next line in the program after 450. In effect, it jumps over the GOTO command line in such cases.

Castle Doors (1:30)

Correct:

48 IF D=2 THEN LET A=RND(30)
62 IF D=5 THEN LET A$="ZOMBIE"

Draw a Picture (1:33)

Some readers have reported difficulties with this program, but it will run as printed. Pay especial attention to the last paragraph. When the program is entered and RUN, you are to respond to the prompt by entering the coordinates of the square you want to fill with a graphics symbol. You are then to respond to the prompt ENTER CHAR CODE with the number of the symbol you want as shown in column 3. Erasing may be done by entering 0 to erase the previous character or by entering the coordinates again and then the new character.

How to Produce a Display File

(2:13, col. 1)

A full screen suggestion:

40 FOR J=1 TO 21

Correct:

60 FOR I=1 TO 30
70 PRINT " "; (1 sp.)

(2:15, col. 1)

Continue adding dummy lines until line 10 is scrolled off the screen. Then delete the dummy lines by entering the line number and NEWLINE before entering the loader program.

(2:15, col. 2)

40 IF A<1 OR A>300 THEN GOTO 30

Truth in Programming (2:19, col. 1)

20 IF X THEN LET T=T+1

Game of Life (2:29)

Change: 450 NEXT I

Add: 460 FOR I=9 TO 55

The graphics given in the program do not produce the * in the square. Hopefully the * makes it easier to see the squares being referred to. For those who want to use the * in the display, change the character number 128 to 222 in lines 120 and 500.

Some readers have pointed out that the game does not follow the rules in the article. Reader Walter Bacon has proposed program changes to bring it closer to the rules (see Letters).

Artillery (2:27)

Readers with 1K have found that the game fills the memory rather quickly. You can increase the memory available for play by trimming down the PRINT statements to very brief prompts or try Reader Joe Dell’Orfano’s program amendments (see Letters).

Tic Tac Toe (2:32)

Add: 445 CLS

More Truth in Programming (3:7, col. 3)

Correct:

IF NOT (X<5 AND Y<8) . . .

Black Hole (3:9)

Correct:

75 IF S<1 OR S>9 THEN GOTO 70

See the Letters for suggestions for trimming this to 1K.

Auto-Display-Changing (3:14)

Dr. Logan reports a bug that occurs because of variations in TV sets: “Some users may find it necessary to use other values in line 64.

64 POKE A+24,3 or 5

in order to get better timing.”

Variable Conversions (3:26)

Correct:

113 IF X=-27 THEN GOTO 116

Forest Treasure (3:34)

Correct:

30 PRINT "▒"; (shift A), or
30 PRINT CHR$(128)
490 delete %

8K Basic ROM and 16K-Byte RAM Pack (3:37)

As a number of readers observed, the actual ROM they received differs somewhat from our article. Between the time we received the materials and the actual production of the 8K ROM a few changes were made.

The following commands were omitted:

DATA
DRAW m,n
NEW n
READ v
RESTORE
UNDRAW m,n

These commands were added:

L PRINT   Prints a string on the printer.
L LIST    Lists the program on the printer.
COPY      Prints the entire screen on the printer. The printer is
          capable of printing all the characters including graphics.

FAST      On the ZX81 there are two modes of operation.
SLOW      On the ZX80 8K keyboard these do not function.

(3:38)

16K RAM Pack: A separate power supply is now being provided.

The ZX80 Keyboard

(3:42)

The author is David Ornstein, [address omitted].

(3:44)

Listing 1 is copyrighted by Sinclair Research.

Graphics Surprises (3:22)

The author is James H. Parsons, [address omitted].