Introduces LKDOS, a new DOS for the Larken disk system that takes the standard Sinclair cassette commands. A series of screens explains the new commands, with examples of each: LOAD, SAVE, CAT, FORMAT, ERASE and OPEN. It also covers the error messages and the differences from the older LDOS. The tape loads two versions of the DOS, one at 50000 for double-sided disks and one at 59000 for single-sided disks. Each is 3,400 bytes and needs a 2K buffer after it, 5,500 bytes in all. At the end, the program offers a drive motor test or to format a blank disk and copy itself and both DOS files onto it. Anything beyond the information screens needs the Larken disk interface and drive.
The opening screen reads "NEW FROM LARKEN ELECTRONICS". Larken Electronics of Canada was run by Larry Kenny. The tape holds the BASIC program LKdemo (autostart line 1300) and the code files LKDS50.CZ and LKDS59.CZ. In the TAP file, block 6 (one of the code blocks) has a bad checksum; the TZX file in the same archive may be the better copy.
Program Analysis
Program Structure
- Lines 1300–1305: the autostart loader. It loads both DOS code blocks and then
RUNs the program. - Lines 3–70:
CLEAR 49999, the title, and a six-noteBEEPfanfare read from DATA. - Lines 100–520: the information screens, each ending with a "PRESS ANY KEY" prompt printed to the lower screen by the subroutine at line 90.
- Lines 650–860: instructions for saving the DOS files to disk, then the choice between the drive test and making a new disk.
- Lines 1200–1255: a tape
SAVEof the program and both code blocks.
What the Screens Describe
- Commands are sent to the DOS after
RAND USR 50000:, or withPRINT #n:once a channel 4–15 has been opened withOPEN #n,"dd". Variables and expressions are allowed in any command, for exampleSAVE a$( TO 6)+".C"+STR$ a CODE A+1,B-A. - File names keep the LDOS type suffixes:
.B1for BASIC,.C1for code and.A1/.A$for numeric and string arrays. Arrays can be loaded under a different name, and do not have to exist in memory first. CATon the 2068 takes a search string and a^wild card. On a Spectrum,CATalone lists the whole directory.- The new error codes are S Protect Error, T File Not Found, U Disk Full, V Wrong File Type and W Invalid Command.
- LKDOS saves only the BASIC program, not the system variables as LDOS did, so BASIC files can move between the 2068 and the Spectrum. LKDOS and LDOS cannot load each other’s BASIC files. Code saved by LDOS can be loaded by LKDOS if the start and length are given.
OUT 87,0andOUT 87,2select drive 1 or drive 2. Disks formatted on a 2068 for use on a ZX81 should hold no file longer than 22 blocks.
Notable Techniques
- The drive test (lines 720–780) turns the motor and LED on and off with
OUT 69,8andOUT 69,0. If nothing happens, the screen says to check the motor jumpers on the drive. - The disk-making routine opens channel 4 on the DOS chosen for the number of sides, then does
FORMAT, threeSAVEs and aCAT, each prefixed withPRINT #4:.
Potential Issues
- Line 710 tests for "s" again instead of "t". As a result, any answer other than S goes on to the drive test.
- The program ends with
GO TO 2000, a line that doesn’t exist, so it simply stops after the new disk is catalogued. - The disk copy is saved with
LINE 1, but the program’s first line is 3, and it does not reload the DOS code on its own the way the tape version does at line 1300.
Image Gallery
Source Code
3 CLEAR 49999
4 PRINT " "; FLASH 1;"NEW"; FLASH 0;" FROM": PRINT
5 PRINT " LARKEN ELECTRONICS"
10 FOR A=1 TO 6: READ C: READ B: BEEP C,B: NEXT A
20 DATA .15,-3,.15,2,.15,6,.3,9,.15,6,.5,9
40 PRINT AT 8,2; BRIGHT 1;"A NEW LDOS THAT SUPPORTS"
50 PRINT AT 10,1;"STANDARD CASSETTE COMMANDS"
60 PRINT : PRINT " FOR THE LARKEN DISK"
70 GO SUB 90: GO TO 100
90 PRINT #0;TAB 5;"PRESS ANY KEY": PAUSE 0: CLS : RETURN
95 PRINT #0;" Press any key when ready": PAUSE 0: RETURN
100 PRINT "Two Dos's are now loaded in memory"
101 PRINT : PRINT "One is loaded at 50000 and One is loaded at 59000": PRINT : PRINT "They are 3400 bytes long but they use a 2 k buffer following the dos so they use a total of 5500 bytes"
110 PRINT : PRINT " IT SUPPORTS :: ": PRINT
115 PRINT "LOAD","SAVE": PRINT : PRINT "CAT","FORMAT": PRINT : PRINT "ERASE","OPEN": PRINT
120 PRINT : PRINT " Its Spectrum Compatible"
130 GO SUB 90
135 PRINT " LDOS TYPE FILE NAMES ARE STILL USED eg: Progrm.B1"
136 PRINT
140 PRINT " ALL VARIATIONS OF LOAD AND SAVE ARE SUPPORTED"
145 PRINT : PRINT "ALSO VARIABLES AND FORMULAS ARE ALLOWED IN ANY COMMAND"
150 PRINT : PRINT "eg: SAVE a$( TO 6)+";CHR$ 34;".C";CHR$ 34;"+STR$ a CODE A+1,B-A"
155 PRINT : PRINT " FORMAT A$,","CAT A$,"
159 GO SUB 90
160 PRINT "RAND USR 50000: OR": PRINT : PRINT "PRINT #N : is used to enable the DOS to interpret the command immediatly following it"
170 PRINT : PRINT "eg: RAND USR 50000: LOAD 'Progrm.B1'"
180 PRINT : PRINT "eg: PRINT #4: CAT '.C',"
190 PRINT : PRINT : PRINT "TO USE THE 'PRINT #N ' COMMAND YOU MUST OPEN THE CHANNEL WITH A RAND USR 50000: OPEN #N,'dd'": PRINT : PRINT " N can be 4 - 15"
195 GO SUB 90
200 PRINT BRIGHT 1;"LOAD commands": PRINT : PRINT
210 PRINT "LOAD 'XXXXX.B1' LOAD 'XXXXX.C1'CODE LOAD 'XXXXX.C1'CODE start LOAD 'XXXXX.C1'CODE start,length"
220 PRINT "LOAD 'XXXXX.A1'DATA z() LOAD 'XXXXX.A$'DATA z$()"
230 PRINT : PRINT "THE '$' MUST BE IN THE FILENAME AFTER THE 'A' FOR STRING ARRAYS": PRINT : PRINT "ARRAYS ARE NOT SAVED AS A SPECIFIC VARIABLE SO AN ARRAY THAT WAS SAVED AS A$() CAN BE LOADED AS Z$()"
232 PRINT : PRINT BRIGHT 1;"ARRAYS NOW DON'T HAVE TO BE ALREADY IN MEMORY AND SIZE IS NOT A FACTOR"
235 GO SUB 90
240 PRINT BRIGHT 1;"SAVE commands": PRINT
250 PRINT : PRINT "SAVE 'XXXXX.B1' SAVE 'XXXXX.B1' LINE # SAVE 'XXXXX.C1' CODE start,lenthSAVE 'XXXXX.C1' SCREEN$ SAVE 'XXXXX.A1' DATA a() SAVE 'XXXXX.A$' DATA a$()"
260 GO SUB 90
270 PRINT BRIGHT 1;"CATALOG": PRINT
280 PRINT : PRINT "For 2068 CAT '', lists all directory CAT 'abc', list all files with the string 'abc' in them CAT 'a^c', lists all files with 'a',any character,and 'c'": PRINT : PRINT "'^' is a 'wild card' character eg: if a disk had files : 'prog1.B1','prog2.B1','prog1.C1 ": PRINT " CAT 'prog^.B1', would list prog1.B1 and prog2.B1"
284 PRINT AT 13,0;" "
285: PRINT " CAT 'prog^.B1', would list prog1.B1 and prog2.B1"
290 PRINT : PRINT : PRINT "For Spectrum": PRINT "CAT lists all directory"
300 GO SUB 90
310 PRINT BRIGHT 1;"FORMAT"
320 PRINT : PRINT : PRINT "FORMAT 'Disk Name', 2068 FORMAT 'Disk Name' Spectrum"
330 PRINT : PRINT "Disk name is 0 - 9 characters"
333 PRINT : PRINT "LKDS50.CZ formats DOUBLE SIDED LKDS59.CZ formats SINGLE SIDED":
338 PRINT : PRINT "Note - Disks formated on a 2068 for use on a ZX81 should not hold files longer than 22 Blocks"
340 PRINT : PRINT BRIGHT 1;"ERASE"
350 PRINT : PRINT "ERASE 'Filename', 2068 ERASE 'Filename' Spectrum "
360 PRINT " File name in erase is not checked for syntax"
395 GO SUB 90
400 PRINT BRIGHT 1;"NEW ERROR MESSAGES"
410 PRINT : PRINT "S Protect Error T File Not Found U Disk Full V Wrong File Type W Invalid Command"
420 PRINT : PRINT "Error V occurs when .A or .C dosn't corrospond with CODE or DATA Also when array type is wrong"
430 PRINT : PRINT " LKDOS checks for free memory before loading Basic and Arrays Standard Sinclair Error messagesare used when apropriate"
440 GO SUB 90
450 PRINT BRIGHT 1;" Differences between : LDOS (2068,ZX-81) and LKDOS "
460 PRINT : PRINT BRIGHT 1;"BASIC Programs": PRINT "LKDOS saves only the program so programs can be loaded between the 2068 and Spectrum LKDOS cannot load BASIC programssaved by LDOS and vice versa "
470 PRINT "LDOS saved all system variables and stack pointer "
480 PRINT : PRINT BRIGHT 1;"CODE": PRINT "The start and length of the codemust be stated when loading codewith LKDOS that was saved with LDOS. After it is resaved with LKDOS it is compatible between both Dos's"
490 GO SUB 90
500 PRINT BRIGHT 1;"ARRAYS": PRINT
510 PRINT " String arrays will need to have the '$' added after the .A"
520 PRINT : PRINT BRIGHT 1;"DUAL DRIVES ": PRINT "OUT 87,0 will select drive 1 OUT 87,2 will select drive 2 (this will be the GOTO command )"
650 PRINT : PRINT "The Dos at 50000 should be savedto disk as 'LKDS50.CZ' The Dos at 59000 should be savedto disk as 'LKDS59.CZ'"
660 GO SUB 90
665 CLS
670 PRINT "Do you want to test your drive to make sure the jumpers are correct Input 'T' to test drive": PRINT : PRINT "OR"
700 PRINT : PRINT "Do you want to save this and theLKDOS's to a new disk": PRINT : PRINT "Press 'S' to save": INPUT a$: IF a$="s" OR a$="S" THEN GO TO 800
710 IF a$="s" OR a$="S" THEN GO TO 720: STOP
720 CLS : PRINT "Press '1' to turn drive motor and LED on Press '2) to turn drive motor and LED off"
722 PRINT "Press 'c' to continue"
725 PRINT AT 14,0;"If motor and LED are not being activated then check motor jumpers on drive"
730 LET a$=INKEY$: IF a$="" THEN GO TO 730
740 IF a$="1" THEN OUT 69,8: PRINT AT 10,0; BRIGHT 1;"Motor ON "
750 IF a$="2" THEN OUT 69,0: PRINT AT 10,0; BRIGHT 1;" Motor OFF"
770 IF a$="c" THEN GO TO 665
780 GO TO 730
800 CLS : PRINT "Put a blank disk in Drive 1": PRINT :
804 PRINT : PRINT : PRINT "Is the disk drive 1 sided or 2 sided (Enter 1 or 2 )": INPUT "Sides ";a
808 IF a=1 THEN RANDOMIZE USR 59000: OPEN #4,"dd"
809 IF a=2 THEN RANDOMIZE USR 50000: OPEN #4,"dd"
810 IF a>=3 THEN GO TO 800
815 PRINT : PRINT " Enter Name of Disk to be FORMATed"
820 INPUT "Disk Name ";a$
830 PRINT #4: FORMAT a$,
840 PRINT #4: SAVE "LKdemo.B1" LINE 1: PRINT #4: SAVE "LKDS50.CZ"CODE 50000,3400
845 PRINT #4: SAVE "LKDS59.CZ"CODE 59000,3400
850 CLS : PRINT #4: CAT "",
860 GO TO 2000
1100 RUN
1200 REM TAPE SAVE
1210 SAVE "LKdemo" LINE 1300:
1250 SAVE "LKDS50.CZ"CODE 50000,3400
1251 SAVE "LKDS59.CZ"CODE 59000,3400
1255 STOP
1300 LOAD "LKDS50.CZ"CODE 50000:
1305 LOAD "LKDS59.CZ"CODE 59000: RUNNote: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.