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0003 The  Boston  Computer  Society 

SINCLAIR-TIMEX  USER  GROUP  NEWSLETTER 

Volume  2,  Issue  1  January  1983 


This  newsletter  is  produced  to  inform  group  members  of  the  agenda  and 
logistics  for  future  meetings,  as  well  as  to  recap  and  amplify  the  information 
provided  at  the  last  meeting.  It  also  provides  a  forum  for  members  and 
interested  parties  to  communicate  what  they  have  learned  or  developed  relating 
to  Sinclair  and  Timex  computer  products.  Meetings  are  open  to  the  public; 
however,  attendees  are  encouraged  to  join  the  Boston  Computer  Society  (BCS). 


NEXT  USER  GROUP  MEETING 

Date:  Wednesday,  January  12,  1983 

Time:  7:00  p.m. 

Place:  Large  Science  Auditorium 

UMass,  Harbor  Campus 
(Directions  on  last  page) 


ACTIVITIES  FOR  THE  JANUARY  MEETING 


The  main  event  for  the  January  meeting  will  be  a  report  from  the  Winter 
Consumer  Electronics  Show  (CES)  by  Sue  Mahoney.  Timex  Computer  Corporation, 
Sinclair  Research,  Ltd.,  Mindware ,  and  perhaps  other  Sinclair-Timex  related 
manufacturers  will  be  at  the  show.  The  show  is  an  annual  affair,  held  in  Las 
Vegas,  Nevada.  It  is  at  the  CES  that  many  manufacturers  introduce  new 
products.  This  year  the  show  runs  from  6  January  till  9  January,  so  Sue's 
report  will  be  timely.  Also,  Sue  plans  to  demonstrate  the  Timex  printer. 

As  in  past  meetings,  we  plan  to  break  up  into  groups  to  discuss  topics  of 
special  interest  following  the  formal  presentations.  Tentatively,  we  will 
break  into  an  advanced  group  and  a  beginner's  group. 


PLANS  FOR  FUTURE  MEETINGS 

The  February  meeting  will  be  held  on  the  16th,  the  third  Wednesday  of  the 
month.  This  is  the  normal  day  for  our  meetings.  If  you  have  items  to  discuss 
at  the  meeting  or  suggestions  for  presentations,  contact  Sue  or  Cliff. 


MIKE  LEVY  ON  BOARD  OF  DIRECTORS 

At  the  General  Meeting  in  December,  Michael  Levy  was  voted  to  the  Board 
of  Directors  of  the  BCS.  Mike  is  President  of  Mindware  Inc.,  a  company 
marketing  hardware  and  software  for  the  Sinclair  and  Timex  computers,  and  has 
been  very  active  in  our  user  group.  Mike  has  long  been  active  in  the  BCS  and 
last  summer  accepted  responsibilities  for  coordinating  activities  of  all 
user/special  interest  groups  in  the  BCS,  an  activity  he  is  retaining  as  a 
member  of  the  Board  of  Directors.  Congratulations  Mike! 


HIGHLIGHTS  FROM  THE  DECEMBER  MEETING 


Sue  Mahoney  opened  the  meeting  with  a  discussion  of  the  benefits  of  BCS 
membership,  which  is  only  $20.  The  BCS  is  the  largest  nonprofit  personal 
computer  association  in  the  United  States.  BCS  members  receive  Computer 
Update ,  a  well  written  magazine  with  nontechnical  computer-related  articles, 
and  the  Calender ,  a  monthly  guide  to  BCS  meetings  and  events.  Members  are 
entitled  to  attend  General  Meetings  (see  back  page)  and  user/special  interest 
group  meetings,  such  as  the  Sinclair-Timex  User  Group.  They  can  also  receive 
any  publications  the  groups  produce.  Other  benefits  include  use  of  the 
Computer  Resource  Center,  and  participation  in  special  discounts  and  events. 
Readers  of  this  newsletter  are  encouraged  to  join  and  become  active  in  the  BCS. 

As  announced,  Mike  Levy  demonstrated  Mindware's  ,!Quickloadn  feature. 
"Quickload”  allows  rapid  and  accurate  loading  of  programs.  All  new  Mindware 
software  comes  with  this  feature.  The  demonstration  was  impressive!  Mike 
loaded  a  large  program  on  the  first  try  after  having  stopped  the  tape  recorder 
halfway  through  the  loading  process.  Loading  with  "Quickload"  is  a  two  step 
process,  but  to  the  user  it  appears  as  one.  First,  a  small  program  is  loaded 
in  the  normal  way.  This  program  loads  running  and  puts  a  couple  hundred  bytes 
of  machine  code  at  the  top  of  RAM.  Then,  the  main  program  is  loaded  by  this 
code.  "Quickload"  is  approximately  4-times  faster  than  the  normal  loading 
technique.  Data  on  a  "Quickload"  tape  is  partitioned  into  blocks.  The  TV 
display  blinks  each  time  a  block  is  read  successfully.  When  an  error  is 
detected,  the  display  goes  blank.  To  recover,  all  the  user  must  do  is  rewind 
the  tape  to  somewhere  ahead  of  the  block  where  the  error  was  detected  and 
restart  the  recorder.  Unfortunately,  the  Mindware  "Quickload"  capability  only 
works  with  original  program  tapes.  That  is,  after  the  program  is  loaded,  you 
cannot  save  the  program  and  reload  it  using  "Quickload."  Tapes  written  by 
your  recorder  can  generally  be  read  by  your  recorder,  so  this  may  not  be  too 
serious  a  limitation.  Mike  says  that  Mindware  is  considering  marketing  the 
"Quickload"  save  capability,  but  he  doesn't  envision  a  large  market  for  it. 

Mike  stated  that  he  and  others  at  Mindware  spent  a  lot  of  time  trying  to 
determine  the  cause  of  tape  loading  problems.  Previously,  he  reported  that 
azimuth  adjustment  was  the  most  important  parameter.  Azimuth  is  adjusted,  on 
many  tape  recorders,  by  turning  a  screw  located  near  the  read/write  head. 

It  is  not  recommended  that  you  change  the  azimuth  setting!  However,  Mindware 
has  found  that  tape  height  is  a  more  critical  parameter.  Mike  stated  that 
many  cassettes  are  banana-shaped  (bent?).  As  a  result,  if  the  tape  is  turned 
over,  a  different  effective  read  height  is  presented  to  the  read  head.  This 
causes  problems. 

Mike  stated  that  Mindware  is  delivering  the  dot  matrix  printer.  The 
printer  is  currently  the  only  FCC  certified  printer  for  the  computer.  There 
was  discussion  about  the  difficulties  in  getting  FCC  certification  and  some  of 
the  fixes  which  were  required,  such  as  ferrite  chokes  on  the  power  cables. 

Rod  Haden,  Mindware's  Vice  President  of  Marketing,  commented  about 
software.  Mindware  is  no  longer  in  the  catalog-sales  business.  They  are  in 
the  mass-merchandizing  business.  Their  software  will  start  appearing  in 
computer  stores  in  the  Boston  area  this  month.  Currently,  Mindware  has  over 
20  software  titles. 

We  were  very  lucky  to  have  Tim  Hartnell  in  attendance.  Tim  is  the  head 
of  the  National  ZX  (pronounced  zed  eks)  User  Club  in  the  U.K. ,  an  organization 
with  10,700  members.  He  is  also  the  author  and  publisher  of  many  books  on 
ZX-80/81  computers.  Three  of  his  more  popular  books  in  this  country  are 
Making  the  Most  of  Your  ZX-81  and  49  Explosive  Games  for  the  ZX-81,  both  by 


HIGHLIGHTS 


Continued 


Res ton  Publishing  Company,  and  Getting  Acquainted  with  your  ZX-81,  by  Creative 
Computing,  Tim  was  in  this  country  arranging  for  the  publication  of  books  and 
magazines  with  which  he  is  associated.  Tim  described  his  experiences  with  the 
ZX-80,  ZX-81,  and  Spectrum  computers  and  answered  questions. 

According  to  Tim,  the  Spectrum,  which  will  be  known  as  the  TS  2000  in 
this  country,  has  many  good  points  but  is  not  yet  completely  debugged.  One 
example  of  a  bug  is  that  the  printer  can  cause  the  machine  to  hang  up.  Tim 
stated  that,  by  the  time  that  the  Spectrum  gets  to  this  country,  the  British 
will  have  found  most  of  the  bugs.  Nobody  knows  when  the  Spectrum  will  arrive; 
Tim  suggested  between  April  and  August.  In  Britain,  they  are  anxiously 
awaiting  the  availability  of  the  Microdrive  (stringy-floppy)  mass-storage 
capability  for  the  Spectrum.  Tim  also  discussed  the  problem  with  the 
RAM  pack  connection.  He  referred  to  the  problem  as  "RAM-Pack  Wobble.”  In 
fact,  Tim  authors  a  column  in  his  newsletter  with  that  title.  Tim  said  that 
Uncle  Clive's  brother  was  responsible  for  the  RAM  pack's  mechanical  design. 
Tim's  solution  is  a  C-clamp  to  secure  the  keyboard  and  RAM  pack  to  a  shelf , 
and  the  use  of  an  external  keyboard.  This  way,  the  computer  never  moves.  He 
said  that  every  serious  British  programmer  has  a  separate  keyboard. 

John  Kemeny  gave  a  description  of  a  TS  1000  video  monitor  interface  which 
he  purchased  from  Random  Access.  Two  versions  are  available.  He  bought  the 
deluxe  version  for  $20.45,  which  allows  inverse  video.  It  appears  well 
designed;  the  documentation  is  well  written  and  complete.  The  only  problem  is 
that  after  he  made  the  modifications  and  installed  the  board,  his  computer 
wouldn't  work.  As  he  had  only  installed  the  mod  the  day  before,  he  hadn't 
gotten  any  of  his  “electrical  engineer  friends"  to  help  him  debug  it.  He'll 
tell  us  how  he  likes  the  interface  when  he  finds  the  problem. 

In  addition,  the  following  announcements  were  made  during  the  meeting: 

.  Henry  April  displayed  the  production  version  of  the  keyboard  he 

designed  and  is  marketing  through  his  company  E-Z  Key.  Henry  first 
told  us  of  the  keyboard  last  July  and  kept  us  informed  throughout  its 
development  process.  The  keyboard  is  larger  than  the  TS  1000 
membrane  keyboard.  It  gives  tactile  feedback,  and  sells  for  $70. 
Henry  says  he  is  now  going  to  develop  another  keyboard  and  market  a 
number  of  TS  1000-related  products. 

.  Dave  Wood  described  the  software  products  he  has  developed  and  is 

selling  through  his  company  Sirius Ware.  He  has  developed  programs  to 
read  and  write  data  onto  tapes,  merge  BASIC  programs,  and  (for  a  64  K 
RAM)  move  BASIC  code  from  above  32  K  into  an  area  where  it  can  be 
executed.  Dave  provided  a  brief  tutorial  about  the  memory 
utilization  in  the  computer. 

.  Mort  Rosenstein  offered  club  members  discounts  on  Softsync  and  Timex 
software  and  Harrison  books  during  the  meeting.  Mort's  company  is 
Atlantic  Northeast  Marketing,  Inc. 

.  Dan  Roy  has  put  together  a  25  chip  color  enhancement  to  his  computer 
and  is  looking  for  person  or  persons  interested  in  assembly  language 
programming  to  join  him  in  the  project. 

.  Will  Stackman  described  Boston's  New  Year  Eve  celebration,  First 
Night,  and  recommended  that  we  catch  the  laser/multimedia. 


BINARY  ON  TWO  HANDS 


Everyone  seems  to  know  that,  internally,  computers  use  binary  numbers. 
Actually,  computers  don't  have  to  use  binary  —  the  old  IBM  1620  didn't.  It 
is  not  necessary  to  know  binary  numbers  (or  numbers  at  all)  to  use  or  even 
program  a  computer.  Therefore,  this  article  is  for  those  curious  about  some 
computer  terminology  and  binary  arithmetic. 

Binary  numbers  are,  if  anything,  simpler  than  the  common  decimal  numbers. 
Decimal  numbers  use  ten  symbols,  0  through  9.  Some  think  this  came  about 
because  people  have  ten  fingers.  Binary  numbers  only  use  two  symbols,  0  and  1. 

In  both  number  systems,  the  "value1'  of  a  digit  is  determined  by  its  place 
in  the  numeric  string.  Moving  left  increases  the  value  by  a  factor.  For 
decimal  numbers,  this  factor  is  10.  Thus,  in  decimal,  "10"  represents  ten 
because  it  equals  the  quantity  1  times  the  place  factor,  10,  plus  0.  Indeed, 
the  one's  place,  ten's  place,  hundred's  place,  and  so  on,  are  so  familiar  that 
the  place  holders  are  taken  for  granted. 

Binary  numbers  behave  just  like  the  decimals,  except  that  moving  left 
increases  the  value  by  a  factor  of  2.  Thus,  in  binary,  "10"  represents  two, 
because  it  equals  the  quantity  1  times  the  place  factor,  2,  plus  0.  The  new 
place  holders  are  one's,  two's,  four's,  eight's,  and  so  on.  The  first  ten 
binary  numbers  are  0,  1,  10,  11,  100,  101,  110,  111,  1000,  1001,  and  1010. 

In  decimal,  the  value  of  the  placeholder  is  reduced  by  the  factor  as  you 
move  right  from  the  decimal  point.  The  "binary"  point  works  the  same  way. 
Remembering  that  the  factor  is  2:  in  binary  .1  is  one-half;  .01  is 
one-quarter.  (One  famous  mathematician  called  the  binary  point,  the  "binary 
decimal"  point.  Another  said  that  this  was  " philologically  incorrect.") 

There  is  nothing  special  about  binary  arithmetic,  either.  The  tables  are 
quite  small.  Addition  goes:  0+0=0,  1+0=1,  0+1=1,  1+1=0  (carry  1),  and 
l+l+(carry  1)=1  (carry  1).  For  example,  1101+111=10100. 

On  the  One  Hand 

After  learning  the  binary  system,  you  might  be  surprised  to  learn  that 
computers  don't  have  numbers  in  them  at  all!  Specifically,  the  Sinclair-Timex 
computer  has  .chips  in  it.  One  of  these  chips  is  called  a  Z80.  It  is  the 
central  processing  unit  or  CPU .  It  contains  registers  and  circuitry  to  carry 
out  instructions .  The  computer  also  has  memory  chips,  ROM  and  RAM.  ROM  is 
read-only  memory.  It  can't  be  changed.  It  contains  the  programs  to  run  the 
system.  RAM,  unlike  ROM,  is  volatile  memory.  That  is,  its  contents  are  lost 
when  the  computer  is  disconnected  from  electricity  (i.e.,  unplugged). 

Registers  and  memory,  alike,  are  divided  up  into  compartments  each 
capable  of  holding  eight  binary  digits  (or  bits)  .  This  8-bit  collection  is 
referred  to  as  a  byte .  Every  byte  in  memory  has  a  unique  name,  called  its 
address .  An  address  is  represented  by  a  consecutive  pair  of  bytes,  sometimes 
called  a  word .  Thus,  the  16-bit  collection  of  binary  digits,  0000000000000000, 
is  the  address  of  the  first  byte  in  memory. 

The  computer  executes  machine  language  instructions,  which  are  operations 
that  cause  the  bits  in  the  registers  and  memory  to  change.  For  example,  there 
is  a  machine  instruction  to  add  two  registers  together  (as  if  they  were  two 
8-digit  binary  numbers)  and  place  the  result  in  one  of  them.  The  point  is 
this:  the  computer  doesn't  know,  or  care,  about  what  the  bytes  in  the 

registers  and  storage  areas  represent.  The  bytes  may  represent  binary 


numbers,  or  codes  for  characters,  or  an  address,  or  even  part  of  a  program. 
Note  that  any  finite  amount  of  bits  can  only  represent  a  finite  amount  of 
numbers.  An  8-bit  byte  allows  256  different  representations,  while  a  16-bit 
word  allows  65,536. 


On  the  Other  Hand 

To  use  numbers  in  a  computer  requires  some  convention  as  to  the 
representation.  At  the  machine  language  level,  the  Z80  hardware  creates  this 
convention.  The  Z80  adds  and  substracts  8-  and  16-bit  integer  numbers  (no 
fractions).  Negative  numbers  are  represented  by  a  convention  called  two's 
complement,  which  has  two  features.  First,  the  leftmost  (also  known  as 
most- sign if icant)  bit  of  all  positive  numbers  is  0,  while  for  all  negative 
numbers,  it  is  1.  Second,  to  subtract  two' s-complement  numbers,  you  need  only 
take  the  two's  complement  of  the  subtrahend  and  add.  Taking  the  two's 
complement  of  a  number  requires  two  steps: 

1.  Change  all  Os  to  Is,  and  Is  to  Os. 

2.  Add  1  to  the  result  of  the  first  step. 

For  example,  the  two's  complement  of  00001010  is  11110110. 

Binary  numbers  with  many  digits  are  cumbersome  to  write.  To  make  things 
easier,  a  notation  is  used  which  groups  four  bits  together.  The  unit  is 
sometimes  called  a  nibble .  Thus,  a  byte  is  made  up  of  two  nibbles.  No  joke. 
In  fact,  although  not  generally  accepted,  in  some  hungry  circles,  a  group  of 
32  bits  is  called  a  chomp  and  a  group  of  64  bits  is  called  a  gulp.  The  Z80, 
however,  can't  work  with  chomps  and  gulps.  There  are  16  different  4-bit 
units,  0000  to  1111,  and  each  is  represented  by  a  single  symbol,  namely,  0,  1, 
...,  9,  A,  B,  C,  D,  E,  and  F.  Thus,  the  unit  1010  becomes  A,  and  the  byte 
11010101  becomes  D5.  This  is  hexadecimal  notation.  For  conversion  from 
decimal  notation  to  hexadecimal,  hex  for  short,  use  the  following: 

PRINT  CHR$  (INT  ( X/16H28)  +CHR$  ( X-INT  ( X/  1 6 ) *  1 6+28 ) 

where  X  is  a  decimal  number,  less  that  256.  Conversion  in  the  other  direction 
can  be  done  using  a  string  variable  for  input  of  the  hex  number: 

1  INPUT  X$ 

2  LET  X=0 

3  FOR  1=1  TO  LEN  X$ 

4  LET  X=X* 16  +  CODE  X$(I)  -  28 

5  NEXT  I 

6  PRINT  X 

1Q  A  very  important  binary  number  is  10000000000,  a  1  followed  by  ten  0s,  or 
2  .  It  is  better  known  by  its  abbreviation,  K.  Its  decimal  value  is  1024, 
and  it  is  the  "binary  thousand." 

The  TS  1000  comes  with  2  K  of  memory.  This  means  it  has  2048  8-bit  bytes 
for  RAM.  Each  Sinclair-Timex  character  and  token  uses  up  (is  represented  by) 

1  byte  of  storage,  so  it  is  customary  to  think  of  2  K  of  memory  as  having  the 
capacity  to  hold  slightly  more  than  2000  characters.  The  16  K  RAM  pack  has 
16,384  bytes.  Since  the  Z80  CPU  uses  a  16-bit  word  for  the  name  of  a  memory 
location  (i.e.,  address),  there  are  2  '  or  64  K  or  65,536  addresses  available. 
Thus,  the  computer  can  directly  address  a  maximum  of  64  K  bytes  memory. 


BUG  #2  (8  K  ROM) 


Last  month  we  began  a  column  talking  about  ROM  bugs.  We  defined  a  bug  to 
be  any  unwanted  characteristic  of  the  computer.  The  bug  described  last  issue 
was  such  that  it  would  probably  not  really  bother  anyone  —  except  your 
editor.  The  bug  described  below  at  first  appears  to  be  equally  unimportant. 
But,  as  explained,  it  could  be  of  great  importance.  Thanks  goes  to  Dave  Wood 
for  pointing  out  this  bug. 

There  are  several  characteristics  of  the  display  which  are  interesting  to 
note.  If  a  statement,  specifically  a  REM  statement,  contains  the  newline 
(enter)  character,  the  display  of  the  statement  will  be  broken  at  the  newline 
character.  The  newline  character  is  a  byte  of  value  118  (76  hex).  To  observe 
this,  enter  the  following: 

1  REM  ROM  BUG 

2  REM  NUMBER  2 

Now  insert  a  newline  character  into  the  first  REM  using  POKE  16517,118.  What 
happens  is  the  computer  sees  the  newline  character  and  creates  a  new  line.  If 
you  try  to  edit  line  1,  you  cannot  move  past  the  newline  character  with  the 
cursor  control  (arrow)  keys.  Now  enter  POKE  16518,118.  Two  adjacent  newline 
characters  make  the  rest  of  the  line  unlistable.  You  cannot  move  past  this 
line  using  the  cusor  down  key.  However,  you  can  still  list  statement  2  to  see 
the  remainder  of  the  program.  This  is  interesting  and  could  be  annoying  in 
some  cases,  but  there  are  reasons  for  these  anomalies  so  we  do  not  classify 
them  as  bugs. 

The  bug  occurs  with  long  REM  statements  containing  a  newline  character. 

If  you  have  lots  of  time  and  are  really  interested,  then  enter  a  REM  statement 
containing  at  least  701  characters.  Enter  a  few  extra  in  case  we  miscounted. 
This  is  a  REM  that  takes  the  entire  display.  When  you  poke  a  newline 
character  anywhere  into  one  of  the  first  700  bytes  of  this  statement,  the 
machine  goes  off  into  Never-Never  land.  The  first  part  of  the  REM,  the  part 
before  the  newline  you  inserted,  will  flash  (if  you  are  in  slow  mode,  else  the 
screen  will  just  go  blank)  and  you  can  never  regain  control  of  the  machine, 
without  pulling  the  plug  and  starting  over.  Exactly  what  the  computer  is 
doing  is  hard  to  tell,  but  to  hang  up  in  this  way  is  definitely  a  bug! 

Now  why  is  this  important?  If  you're  writing  machine  language  programs 
and  you  store  the  code  in  a  REM,  you  could  encounter  this  condition.  Even  if 
you  never  want  to  create  a  REM  statement  that  is  over  700  characters  in 
length,  let  alone  one  with  a  newline  character  in  it,  this  bug  could  still 
affect  you.  It  could  (we  don't  know  if  it  is)  be  used  to  protect  software. 

By  putting  one  or  more  large  REM  statements  within  a  program,  the  bug  could 
effectively  prevent  listing  a  program. 

HYPOTROCHOID ,  COULDN'T  YOU  TELL 

The  design  on  the  first  page  was  produced  by  Dave  Wood  using  a  program 
from  "Meditations  on  a  Hypotrochoid"  by  Bradley  Rogers  in  the  November/ 
December  1982  issue  of  Sync .  By  varying  the  numbers  in  lines  30  and  40,  a 
number  of  interesting  graghs  can  be  generated. 


TELECOMMUNICATING 


The  Source  is  a  commercial  computer  information/data  base  service  which 
is  accessed  via  telephone  lines  using  a  modem  attached  to  your  personal 
computer.  It  provides  the  capability  to  send  messages  to  other  users  of  the 
Source  across  the  country  and  access  to  various  data  files.  There  are  monthly 
and  usage  fees  for  the  Source.  Both  the  Source  and  CompuServe,  a  competing 
service,  are  a  concern  of  the  Telecommunications  User  Group  of  the  BCS. 

The  Sinclair-Timex  computers  can  access  the  Source  using  a  modem. 

Sinclair  Research,  Inc.  has  established  an  account  on  the  Source.  The  account 
number  is  ST7522.  Skip  Hammel  will  be  at  the  Sinclair  end  of  the  account. 

Skip  has  been  a  long  time  contributor  to  the  group  and  works  part-time  for 
Sinclair,  manning  the  Sinclair  Tech  Line.  Skip  currently  accesses  the  Source 
via  his  Apple  computer  and  is  looking  for  items  of  general  interest  to  enter 
into  the  Source. 


At  the  December  BCS  General  Meeting,  it  was  announced  that  the  BCS 
bulletin  board  was  up  and  running.  Unlike  the  Source,  the  BCS  bulletin  board 
is  totally  free,  except  for  the  price  of  the  telephone  call.  The  number  for 
the  bulletin  board  is  (617)  969—9660.  Information  for  each  user/special 
interest  group  of  the  BCS  will  be  maintained  and,  perhaps,  we  will  be  able  to 
use  this  service  as  a  means  of  communications  —  when  we  all  get  modems. 

NEED  A  CLOCK?  (8  K  ROM) 


In  the  ROM  Bug  #1  article  in  the  last  newsletter,  we  stated  that  the 
system  variable  FRAMES  is  decremented  60  times  a  second  (in  slow  mode).  Below 
is  a  program  which  uses  this  fact  to  provide  a  time  of  day  clock: 


10  PRINT  "ENTER  HOUR" 

20  INPUT  H 

30  PRINT  "ENTER  MINUTE" 

40  INPUT  M 

50  PRINT  "ENTER  SECOND" 

60  INPUT  S 

70  LET  L=PEEK  16436  +  256*PEEK  16437 
80  LET  X=PEEK  16436  +  256*PEEK  16437 
90  LET  D=(L-X+(L-X<0)*32768)/60 
100  LET  S=S+D 
110  LET  L=X 

120  IF  S<60  THEN  GOTO  160 
130  LET  S=S-60 
140  LET  M=M+1 
150  GOTO  120 

160  IF  M<60  THEN  GOTO  200 
170  LET  M=M-60 
180  LET  H=H+1 

190  IF  H>23  THEN  LET  H=H-24 

200  PRINT  AT  10,10;(STR$  (100+H))(2  TO  );":";(STR$  (100+M)) 
(2  TO  );":";( STR$  (100.5+Sl7(2  TO  3) 

210  GOTO  80 


The  clock  is  as  accurate  as  the  ceramic  filter  (in  this  computer  its  not  a 
crystal)  which  clocks  the  computer.  Accuracy  can  be  improved  by  adding 

95  LET  D=D*F 


where  F  is  a  value  close  to  1  chosen  to  compensate  for  the  measured  error. 


GENERAL  MEETING  EVENTS 


The  BCS's  January  26  General  Meeting  will  feature  the  first  public 
showing  of  two  major  new  personal  computers  from  Apple  Computers  Inc.  The 
meeting  is  at  7:30  at  the  New  England  Life  Hall  on  Clarendon  Street,  Boston. 
There  will  be  a  $3.00  charge  for  nonmembers.  Call  Mary  McCann  in  the  BCS 
office  for  more  information.  In  March,  Gary  Kildall  of  Digital  Research  and 
creator  of  CP/M  will  talk  at  the  General  Meeting. 


FOR  MORE  INFORMATION 

Sue  Mahoney,  Director  of  the  Sinclair-Timex  User  Group 
c/o  The  Boston  Computer  Society  or  call  (203)  573-5816. 

Cliff  Danielson,  Newsletter  Editor 

14  Davis  Road,  Chelmsford,  MA  01824,  (617)  256-4638. 

John  Kemeny,  Contributing  Editor  &  Correspondent  With  Other  User  Groups 
284  Great  Road,  Apt.  D5,  Acton,  MA  01720. 


DIRECTIONS  TO  THE  MEETING 

The  Sinclair-Timex  User  Group  meets  in  the  Large  Science  Auditorium  (Room 
8/2/009)  of  the  University  of  Massachussets  of  Boston,  Harbor  Campus.  The 
Harbor  Campus  is  only  3  miles  from  downtown  Boston  and  easily  accessible  by 
public  and  private  transportation.  From  the  north  or  west,  take  the  Southeast 
Expressway  to  Exit  17.  Turn  left  onto  Columbia  Road.  Enter  the  rotary  and 
take  the  first  right  (Morrissey  Boulevard).  Bear  right  on  the  traffic  island, 
following  UMass/Boston  sign.  Turn  left  into  the  Campus.  From  the  south,  take 
Morrissey  Boulevard  northward  to  the  campus.  On  the  MBTA,  take  the  Red  Line 
(Ashmont  Train)  to  Columbia  Station.  Transfer  to  the  free  University 
shuttlebus  in  the  T  parking  lot. 


IMPORTANT  NOTICE  !  !  !  .if  the  mailing  label  on  this  newsletter  is 

handwritten,  then  you  are  not  on  the  mailing  list  of  the  Sinclair-Timex  User 
Group.  You  need  to  either  join  the  BCS  or,  if  you  are  a  BCS  member,  contact 
Mary  McCann  in  the  BCS  office  to  be  added  to  the  Sinclair-Timex  mailing  list. 


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