ZX80 Prestel Model

This program is a model of the British Prestel data base tree structure. It can be used with your own data for display to show how Prestel data is accessed. This version fits in 1K; if you have 16K and lots of patience, you could create and record an impressive dictionary in a given field.

From EZUG Newsletter, No. 3, pp. 7-8, Apr/May 81, Highgate School, Balsall Heath Rd, Birmingham, B12 9DS, UK. Reprinted by permission.

(Note–Prestel is an on-line data base retrieval system run by the British Post Office. Meant for the public, it uses phone lines and home TV sets and resembles the US Source network in theory. This program is complete for choice 1. Choices 2, 3, & 4 are only place holders; they contain no data yet. Try this format to create sequentially accessed data, as in choice 1. Prestel doesn’t fit in 1K RAM with 8K ROM, so we give no 8K Syntactic Sum.)

  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 RETURN
Syntactic Sum=-16780,4K