A model of Prestel, the British Post Office’s viewdata service, reprinted by Syntax from the newsletter of EZUG, a UK ZX80 users’ group. RUN shows an index of numbered choices; choosing 1 leads to a sub-index and pages 11 to 13 with short notes on electricity (USE V=IR and so on), each ending with N/L TO RETURN TO INDEX. Choices 2 to 4 are placeholders for pages you add yourself, and 0 stops the program.
As printed, choice 4 runs into the STOP in line 4990 instead of returning to the index. It fits in 1K.
Published in Syntax June 1981 (ZX80 Prestel Model).
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Source Code
10 LET A=0
20 GO SUB 5000
30 LET A$= "TYPE NUMBER NEEDED"
40 PRINT A$
50 GO SUB 5100
60 PRINT "1. V, I, R"
70 PRINT "2. CIRCUIT EQUATION"
80 PRINT "3. POWER"
90 PRINT "4. RESISTORS"
100 GO SUB 5100
110 PRINT "OR TYPE 0 TO STOP"
120 INPUT B
130 CLS
140 IF B=0 THEN STOP
150 IF B<0 OR B>4 THEN GO TO 10
160 GO TO B*1000
1000 LET A=1
1010 GO SUB 5100
1020 PRINT A$
1030 GO SUB 5100
1040 PRINT "1. TO GET V"
1050 PRINT "2. TO GET I"
1060 PRINT "3. TO GET R"
1070 GO SUB 5100
1080 INPUT B
1090 CLS
1100 IF B<1 OR B>3 THEN GO TO 1000
1110 GO TO 1100+B*100
1200 LET A=11
1210 GO SUB 5000
1220 PRINT "USE V=IR"
1230 GO SUB 5200
1300 LET A=12
1310 GO SUB 5000
1320 PRINT "USE I=V/R"
1330 GO SUB 5200
1400 LET A=13
1410 GO SUB 5000
1420 PRINT "USE R=V/I"
1430 GO SUB 5200
2000 PRINT 2000
2010 GO SUB 5200
3000 PRINT 3000
3010 GO SUB 5200
4000 PRINT 4000
4990 STOP
5000 FOR C=2 TO 11
5010 PRINT " ";
5020 NEXT C
5030 PRINT "PAGE ";A
5040 GO SUB 5100
5050 RETURN
5100 FOR C=1 TO 3
5110 PRINT
5120 NEXT C
5130 RETURN
5200 GO SUB 5100
5210 PRINT "N/L TO RETURN TO INDEX"
5220 INPUT C$
5230 CLS
5240 GO TO 10
5250 RETURNNote: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.