LISTS

This file is part of and CATS Library Tape 3. Download the collection to get this file.

Date: 198x

Type: Program

Platform(s): TS 2068

This program implements a general-purpose flat-file database manager allowing the user to define custom field names and lengths, then add, change, delete, list, search, sort, and save records to cassette tape. Records are stored in a two-dimensional string array `I$(M,J)`, where field boundaries are tracked in a `D(N1,2)` array holding start and end column positions for each field within each record row. The sort routine at line 6000 uses a selection sort (sometimes called a bubble sort in the listing’s own REM) operating directly on the string array slices. A dynamic memory calculation at line 8380 estimates the maximum number of records the available RAM can hold, and the `FREE` keyword is used at line 8433 to display current free memory to the user.

Program Analysis

Program Structure

The program is organized around a main menu dispatcher at lines 200–580. After collecting a numeric choice A (1–9), line 570 uses the computed GO SUB A*1000 to jump directly to each module. Each module occupies a thousand-line block and ends with RETURN, sending control back to the menu loop at line 580.

Line block	Module
1000–1950	Add records
2000–2950	Change a record
3000–3950	Delete a record
4000–4950	List all records
5000–5950	Search for a record
6000–6950	Sort records
7000–7900	Save to tape
8000–8950	Set up new file
9000–9900	List field names

Data Model

The schema is defined dynamically during “Set up new file” (module 8000). The user specifies the number of fields N1, a label width K, and per-field lengths. Field names are stored in N$(N1,K). The two-dimensional array D(N1,2) records the start (D(I,1)) and end (D(I,2)) column offsets within each record string. All record data is held in I$(M,J), where M is the user-requested record capacity and J is the total character width of one record (sum of all field lengths). Individual fields are accessed via string slicing: I$(N,D(I,1) TO D(I,2)).

Key BASIC Idioms and Techniques

Computed GOSUB: Line 570 uses GO SUB A*1000 — an arithmetic expression as the target — to dispatch to any of the nine modules without a chain of IF/THEN tests.
String-slice assignment: Fields are written directly into sub-ranges of I$(N,...) and I$(A,...) via INPUT I$(N,D(I,1) TO D(I,2)), exploiting the language’s ability to assign to a string slice in place.
FREE keyword: Line 8433 uses PRINT ~ (the FREE keyword on the TS2068) to display available memory alongside the calculated maximum record count.
PAPER attribute in PRINT: Several lines use inline PAPER 5 and PAPER 7 within PRINT statements to highlight values on screen without changing the global attribute.
Memory estimation: Line 8380 computes M=INT((27000-N1*(31-L+12))/J) to estimate how many records will fit in RAM, giving the user guidance before the final DIM I$(M,J) at line 8450.

Search Module (5000–5950)

The search performs a linear scan over all N records (lines 5160–5190). The search string A$ is compared against the beginning of the chosen field using I$(J,D(I,1) TO A), where A is recalculated at line 5129 to be D(I,1)+LEN(A$)-1. This means the search is a leading-substring match rather than a full-field match. When a match is found, subroutine 5500 displays the record and asks whether to continue; setting Q=1 exits the loop early.

Sort Module (6000–6950)

The sort at lines 6170–6260 is described in its own REM as a bubble sort but is structurally a selection sort: the outer loop variable J advances from 1 to N-1, and the inner loop K runs from J to N, swapping I$(J) and I$(K) (full record strings) whenever the chosen field of record J is lexicographically greater than that of record K. Whole-record swaps via B$ preserve all field data.

List / Print Module (4000–4950)

The user may choose to print all fields or a subset. Selected field indices are stored in A(J) (reusing the A array dimensioned at line 8184). Output can go to screen or printer; however, the printer path has a structural bug: lines 4610–4690 contain FOR/NEXT loops and LPRINT statements but there is no GO TO 4610 or similar branch from line 4250. Line 4250 tests IF A$(1)="P" THEN GO TO 4600, but line 4600 does not exist in the listing — execution falls through to line 4610, skipping the outer FOR I=1 TO N loop header that would normally set up I, so LPRINT output would be malformed or cause an error.

Save Module (7000–7900)

Module 7000 saves data using SAVE L$ at line 7070, where L$ is the list name entered during setup. After saving, line 7900 uses GO TO 100 — a REM line — rather than RETURN. This unconditionally restarts the program from near the top (falling through to the main menu at line 210) instead of returning normally, which is an intentional design choice to reinitialize the menu display after a tape operation.

Bugs and Anomalies

Printer path missing loop header: GO TO 4600 at line 4250 targets a non-existent line; execution resumes at 4610 inside what should be a double FOR loop, but neither FOR I nor FOR K has been established, making the LPRINT section non-functional.
Search boundary uses D(1,2) instead of D(I,2): Line 5126 reads IF A<=(D(1,2)-D(I,1)+1); the first index should likely be I, not 1, so field-width clamping is only correct when searching field 1.
Add record decrements then caps N: Line 1010 increments N before checking the limit at line 1030–1032, then sets N=M on overflow. This means if the file is full, N is incremented and immediately reset, leaving the count correct, but the logic flow is slightly fragile.
SAVE saves only data, not program: SAVE L$ without additional keywords saves the BASIC program itself, not the data arrays, so reloading would restore the program but not the records — a fundamental limitation of the save strategy.

Content

Appears On

CATS Library Tape 3

Capital Area Timex Sinclair User Group’s Library Tape.

Image Gallery

Source Code
REM "THIS IS A PROGRAM THAT WAS PRINTED IN THE MARCH ISSUE OF MICROCOMPUTING FOR THE ZX 1000. IT HAS BEEN CONVERTED FOR USE ON THE 2068"
REM A LISTS PROGRAM FOR THE 2068
REM MAIN MENU
CLS 
BORDER 2: BRIGHT 1
PRINT TAB 7;"THE LISTS PROGRAM"
PRINT 
PRINT "1..ADD RECORD"
PRINT 
PRINT "2..CHANGE RECORD"
PRINT 
PRINT "3..DELETE RECORD"
PRINT 
PRINT "4..LIST ALL RECORDS"
PRINT 
PRINT "5..SEARCH FOR A RECORD"
PRINT 
PRINT "6..SORT RECORDS"
PRINT 
PRINT "7..SAVE RECORDS TO TAPE"
PRINT 
PRINT "8..SET UP NEW FILE"
PRINT 
PRINT "9..LIST FIELDS"
PRINT 
PRINT 
PRINT "WHICH DO YOU WISH TO DO?";
INPUT A
LET A=INT A
IF A>0 AND A<10 THEN GO TO 560
CLS 
PRINT "PLEASE CHOSE 1-9"
GO TO 230
CLS 
GO SUB A*1000
GO TO 210
REM ADD RECORDS
LET N=N+1
PRINT 
PRINT "RECORD NUMBER ";N
IF N<=M THEN GO TO 1060
LET N=M
PRINT 
PRINT "NO MORE RECORDS CAN BE ADDED"
GO TO 1920
FOR I=1 TO N1
PRINT 
PRINT N$(I);
INPUT I$(N,D(I,1) TO D(I,2))
PRINT I$(N,D(I,1) TO D(I,2));
PRINT 
NEXT I
PRINT 
PRINT "CHANGE ANYTHING?";
INPUT A$
PRINT 
IF A$(1)="Y" THEN GO TO 1060
PRINT 
PRINT "RECORD ";N;" ADDED" 
PRINT 
PRINT "ADD MORE RECORDS?";
INPUT A$
PRINT 
IF A$(1)="Y" THEN CLS : GO TO 1000
RETURN 
REM CHANGE A RECORD
PRINT 
PRINT 
PRINT "TO CHANGE A RECORD, YOU MUST",,," ENTER THE RECORD NUMBER FOR",,," THAT RECORD. DO YOU WISH TO",,,"SEARCH FOR THE RECORD NUMBER?";
INPUT A$
PRINT 
IF A$(1)="Y" THEN GO SUB 5000
CLS 
PRINT 
PRINT "RECORD NUMBER TO CHANGE: ";
INPUT A
LET A=INT A
PRINT 
IF A>0 AND A<=N THEN GO TO 2200
PRINT "INVALID RECORD NUMBER"
GO TO 2900
FOR I=1 TO N1
PRINT 
PRINT N$(I);I$(A,D(I,1) TO D(I,2))
PRINT 
PRINT TAB 10;"CHANGE?";
INPUT A$
PRINT 
IF A$(1)<>"Y" THEN GO TO 2300
PRINT N$(I);
INPUT I$(A,D(I,1) TO D(I,2))
PRINT I$(A,D(I,1) TO D(I,2))
PRINT 
NEXT I
PRINT 
PRINT "FINISHED WITH RECORD ";A
PRINT 
PRINT "CHANGE OTHER RECORDS?";
INPUT A$
PRINT 
IF A$(1)="Y" THEN GO TO 2000
RETURN 
REM DELETE A RECORD
IF N>0 THEN GO TO 3060
PRINT 
PRINT "NO RECORDS IN FILE"
GO TO 3330
PRINT 
PRINT "ITEMS ARE DELETED BY RECORD"
PRINT 
PRINT "NUMBER. RECORD NUMBERS MAY",,,"CHANGE AFTER ITEM IS DELETED"
PRINT 
PRINT "DO YOU WISH TO SEARCH FOR THE",,,"RECORD?";
INPUT A$
PRINT 
IF A$(1)="Y" THEN GO SUB 5000
PRINT 
PRINT "RECORD NUMBER TO DELETE:";
INPUT A
LET A=INT A
IF A>0 AND A<=N THEN GO TO 3250
PRINT 
PRINT "INVALID RECORD NUMBER"
GO TO 3900
FOR I=1 TO N1
PRINT 
PRINT N$(I);I$(A,D(I,1) TO D(I,2))
NEXT I
PRINT 
PRINT "DELETE THIS RECORD?";
INPUT A$
IF A$(1)="Y" THEN GO TO 3360
PRINT 
PRINT "DELETE CANCELLED"
GO TO 3900
IF A=N THEN GO TO 3450
FOR I=A TO N-1
LET I$(I)=I$(I+1)
NEXT I
LET N=N-1
PRINT 
PRINT "RECORD DELETED"
PRINT 
PRINT "DELETE ANY OTHER RECORDS?";
INPUT A$
PRINT 
IF A$(1)="Y" THEN GO TO 3010
RETURN 
REM LIST RECORDS
PRINT 
LET A=0
PRINT "PRINT ALL RECORD FIELDS?";
INPUT A$
IF A$(1)="Y" THEN LET A=1
PRINT 
FOR I=1 TO N1
LET A(I)=A
IF A=1 THEN LET A(I)=I
NEXT I
LET J=N1
IF A=1 THEN GO TO 4220
PRINT 
PRINT "ENTER Y FOR EACH FIELD",,,"YOU WANT PRINTED:"
LET J=0
PRINT 
FOR I=1 TO N1
PRINT 
PRINT N$(I);" ?";
INPUT A$
PRINT A$(1)
IF A$(1)<>"Y" THEN GO TO 4210
LET J=J+1
LET A(J)=I
NEXT I
PRINT 
PRINT "PRINT TO SCREEN OR PRINTER(S/P)"
INPUT A$
IF A$(1)="P" THEN GO TO 4600
PRINT 
PRINT TAB 10; PAPER 5;" ";L$;" "; "LIST"
FOR I=1 TO N
FOR K=1 TO J
PRINT 
PRINT N$(A(K));I$(I,D(A(K),1) TO D(A(K),2))
NEXT K
NEXT I
GO TO 4900
LPRINT TAB 5;L$;" LIST"
LPRINT 
LPRINT N$(A(K));I$(I,D(A(K),1) TO D(A(K),2))
NEXT K
LPRINT 
NEXT I
PRINT 
PRINT "ANOTHER LIST?";
INPUT A$
IF A$(1)="Y" THEN GO TO 4000
RETURN 
REM SEARCH FOR RECORD
PRINT 
PRINT "WHICH FIELD TO SEARCH ON:"
FOR I=1 TO N1
PRINT 
PRINT N$(I);" ?"
INPUT A$
IF A$(1)="Y" THEN GO TO 5100
NEXT I
PRINT 
PRINT "SELECTION CANCELLED"
GO TO 5900
PRINT 
PRINT "ENTER THE SEARCH STRING";
INPUT A$
LET A=LEN A$
IF A<1 THEN GO TO 5110
IF A<=(D(1,2)-D(I,1)+1) THEN GO TO 5129
LET A=(D(I,2)-D(I,1)+1)
LET A$=A$(1 TO A)
LET A=A-1+D(I,1)
LET F=0
LET Q=0
FOR J=1 TO N
IF A$=I$(J,D(I,1) TO A) THEN GO SUB 5500
IF Q=1 THEN GO TO 5200
NEXT J
PRINT 
PRINT "SEARCH COMPLETE"
PRINT 
IF F=0 THEN PRINT "RECORD NOT FOUND"
GO TO 5900
PRINT 
PRINT "RECORD NUMBER ";J
FOR K=1 TO N1
PRINT 
PRINT N$(K);I$(J,D(K,1) TO D(K,2))
NEXT K
PRINT 
PRINT "CONTINUE SEARCH?";
INPUT B$
IF B$(1)="N" THEN LET Q=1
LET F=1
RETURN 
PRINT 
PRINT "ANOTHER SEARCH?";
INPUT A$
IF A$(1)="Y" THEN GO TO 5000
RETURN 
REM BUBBLE SORT RECORDS
PRINT 
PRINT "SORTING TIME DEPENDS ON ",,,"NUMBER OF RECORDS"
PRINT 
PRINT "WHICH FIELD TO SORT BY:"
PRINT 
FOR I=1 TO N1
PRINT 
PRINT N$(I);" ?";
INPUT A$
IF A$(1)="Y" THEN GO TO 6150
NEXT I
PRINT 
PRINT "SORT CANCELLED"
GO TO 6900
PRINT 
FOR J=1 TO N-1
FOR K=J TO N
IF I$(J,D(I,1) TO D(I,2))<=I$(K,D(I,1) TO D(I,2)) THEN GO TO 6250
LET B$=I$(J)
LET I$(J)=I$(K)
LET I$(K)=B$
NEXT K
NEXT J
PRINT 
PRINT "SORT COMPLETE"
PRINT 
PRINT "SORT ON ANOTHER FIELD?";
INPUT A$
PRINT 
IF A$(1)="Y" THEN GO TO 6000
RETURN 
REM SAVE PROGRAM TO TAPE
PRINT 
PRINT "PUT CASSETTE IN TAPE RECORDER",,,"BEGIN RECORDING, THEN",,,"PRESS ANY KEY TO SAVE LIST";
IF INKEY$="" THEN GO TO 7050
PRINT 
SAVE L$
GO TO 100
REM SET UP NEW LIST
PRINT "WHAT LIST NAME TO USE?";
INPUT L$
PRINT TAB 10; PAPER 5;"**";L$;"**"
PRINT 
PRINT "HOW MANY RECORD FIELDS ? ": INPUT N1
PRINT TAB 10; PAPER 5;"  ";N1;"  "
PRINT 
LET K=15
PRINT "ENTER MAX. NUMBER OF CHARACTERS IN DESCRIPTIONS +1 (LIMIT 15)";
INPUT K
PRINT TAB 10; PAPER 5;"  ";K;"  "
IF K>15 THEN LET K=15
IF K<0 THEN LET K=0
PRINT 
LET L=31-K
PRINT "MAXIMUM SIZE OF DATA FIELD IS";TAB 10; PAPER 5;"  ";L;"  "; PAPER 7;" CHARACTERS"
DIM N$(N1,K)
DIM A(N1)
DIM D(N1,2)
PRINT 
PRINT 
PRINT "NOW ENTER FIELD DESCRIPTIONS","AND FIELD LENGTHS:";
LET J=1
PRINT 
FOR I=1 TO N1
PRINT 
LET A$=""
PRINT "FIELD ";I;":";
INPUT A$
PRINT TAB 15; PAPER 5;" ";A$;" "
LET A$=A$+"               "
LET N$(I)=A$
PRINT 
PRINT "FIELD LENGTH (1-";L;"):";
INPUT A
IF A<1 THEN LET A=1
IF A>L THEN LET A=L
PRINT TAB 25; PAPER 5;" ";A;" "
LET D(I,1)=J
LET J=J+A
LET D(I,2)=J-1
PRINT 
NEXT I
LET J=J-1
LET N=0
LET M=INT ((27000-N1*(31-L+12))/J)
PRINT 
PRINT "MAXIMUM NUMBER OF RECORDS",,,"POSSIBLE IS ABOUT ";M  
PRINT 
PRINT "MEMORY FREE ";
PRINT ~
PRINT 
PRINT "HOW MANY RECORDS DO YOU WANT?";
INPUT A
LET A=INT A
IF A>0 AND A<M THEN LET M=A
DIM I$(M,J)
PRINT 
PRINT L$;" LIST SET UP"
PRINT 
PRINT "PRESS ANY KEY TO RETURN TO MENU"
IF INKEY$="" THEN GO TO 8940
RETURN 
REM LIST FIELDS
PRINT 
PRINT TAB 5;L$;" LIST FIELDS"
PRINT 
FOR I=1 TO N1
PRINT 
PRINT 
PRINT N$(I)
NEXT I
PRINT 
PRINT "PRESS ANY KEY TO RETURN TO MENU";
PRINT 
IF INKEY$="" THEN GO TO 9110
RETURN 

Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.

Program Analysis

Program Structure

Data Model

Key BASIC Idioms and Techniques

Search Module (5000–5950)

Sort Module (6000–6950)

List / Print Module (4000–4950)

Save Module (7000–7900)

Bugs and Anomalies

Content

Appears On

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Source Code

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