››=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-›› (KNOWLEDGE  IS  NEVER OLD, ITS ALWAYS›CURRENT.  This  old  article  is worth›reading. Ye Ol Editor.) ››          SYNFILE+ PAGE››           Data File Specifications›April 30, 1985›Copyright 1985 Daniel L. Moore›REPRINTED from ACE Newsletter›December, 1987›››     There are actually four different›files   that   together  make  up  one›SynFile+  datafile.   The files can be›identified  by  their extenders.  They›are  .TBL,  .CNF, .IDX, and .Dxx.  The›.TBL  file  contains  a description of›the  database  form.   The  .CNF  file›contains  the  number  of  records and›disks.   The  .IDX file is the current›index  data.   And, the .Dxx files are›the actual data files.››THE .TBL FILE››     The .TBL file is actually made up›of   three   tables  and  two  numeric›entities.   The  three  tables are the›Definitions  table, the Name table and›the Special Data table.  Each table is›headed by a two byte length entry, and›then the data bytes.  If the table has›a  zero length, there is only a length›entry.››THE DEFINITIONS TABLE››     The  first table, the Definitions›table,   consists  of  a  sequence  of›eleven  bytefield  definitions.  There›is  one  entry  for  each field in the›database.   The  format  of each entry›is:››Byte # Use›  0  screen column position›  1  screen row position›  2-3   field  name  offset  and  name›length›  4  field type byte›  5  field data length›  6  field mask length›  7    field  special  offset  (low  8›bits)›  8  field data offset (low 8 bits)›  9   field  data offset (high 3 bits)›field special offset›     (high 5 bits)› 10  field decimal position››     The  first  two bytes simply give›the  row  and  column  position of the›start  of  the field name.  The screen›is  40  columns by 21 lines and 0,0 is›the upper left hand corner.››     The field name is actually stored›in  the second data table.  The low 11›bits  of  this  16  bit  entry are the›offset  to  the field name in the Name›table.   The high 5 bits are the field›name length.››     The  low  four  bits of the field›type  entry,  identify the field type.›The  high  bit  of the field type is a›flag  for  the  justification  of  the›field.   If  it  is  set, the field is›right  justified.   There  are  eleven›field types in SynFile+ and each has a›number associated with it.  They are:››  ID number Field Type›   0  ASCII field›   1  floating point›   2  cumulative computed›   3  table look-up›   4  dollar›   5  record number›   6  date›   7  integer›   8  counter›   9  conditional›  10  computed››     The  field  data  length  is  the›length  of the data stored in the disk›record.   For  ASCII fields, it is one›greater  than  the  field mask length.›For floating point, cumulative, dollar›and  computed  fields,  it is 6 bytes.›For   table  look-up  and  conditional›fields,  it  is  one  byte.  All other›fields have a data length of 2 bytes.››     The  field  mask  length  is  the›length of the mask(underlines) for the›characters respectively.››     The  special  offset  is  13 bits›split between byte 7 and 9. Byte 7 has›the  low  8  bits  of  data,  and  the›Special Data table has the high 5.  It›is   used   by  computed,  cumulative,›conditional  and table look-up fields.›The   counter  field  also  uses  this›entry,  but not as a pointer.  Counter›fields use it as the increment for the›field.››     The field offset is 11 bits long.› The  low 8 bits are stored in byte 8,›and  the high 3 bits are stored in the›low  3  bits  of  byte  9. This is the›offset from the start of the record to›the   start  of  the  data  from  this›field.››     The  field  decimal  position  is›just  that.   It  tells SynFile how to›display  floating  point numbers.  The›current  version  of SynFile only uses›the low 4 bits of this byte.››     The   others   are  reserved  for›future use.  If the value of this byte›is  15, the field will be displayed in›floating  point,  which is - however -›the  Atari  FP ROM formats the number.›For  any  other  value,  SynFile  will›force  the  display of a decimal point›and  N  digits  to  the  right  of the›decimal.››THE NAME TABLE››     The  Name  table contains all the›field   names.   Each  field  name  is›stored   as  a  text  entry,  with  no›delimiters   or   separators   between›entries.   The names may NOT be stored›in   the  same  order  as  the  fields›entries  in the Definitions table(this›may occur if the form is edited in the›CREATE module of SynFile).››THE SPECIAL DATA TABLE››     The  Special  Data table contains›all  formulas  and table look-up field›datas.››FORMULAS››     Formulas       for      computed,›cumulative, and conditional fields are›stored   as   a  sequence  of  command›tokens.   The CREATE module parses the›user  entered formula, and converts it›to   a   tokenized  RPN  formula.   As›retrieved,  all commands use the top 1›or  2  entries from the stack.  If the›high  bit  of a token is set, then the›field  referenced is an integer(16 bit›data)     field,    a    FLOAT    will›automatically be executed on the field›when   the  data  is  retrieved.   The›command tokens are:››  TOKEN VALUE COMMAND›   0  +  (add the top two values)›   1   -  (subtract the top value from›second value)›   2  *›   3  /›   4  LOG (take the natural LOG of top›number)›   5   LOG10  (take  the common log of›top number)›   6  EXP›   7  EXP10›   8  ABS›   9  SORT›  20  numeric constant›  30   =   (set  true  flag  if  top 2›entries are equal)›  31  >›  32  <›  33  <>›  34  >=›  35  <=› 126  current data› 127  END (end of formula flag)››     Numeric  constants(20) are stored›in  6  byte  internal  floating  point›representations    of    the   number.›Entries 30 to 35 are used to compare 2›numbers   on  the  stack  for  use  in›conditional operations.››     To  interpret  a  computed field,›use  the  special data offset to set a›pointer  to the formula.  The retrieve›tokens  one  byte  at a time until the›END  token is found.  The value on the›top  of  the stack at that time is the›result of the calculation.››TABLE LOOK-UP››     Table  Look-up entries are stored›in  packed  entries(the  lenght of the›entries  is equal to the length of the›longest   entry,   not   to  the  mask›length).   The  field data for a table›look-up   field  is  the  table  entry›number.   The  first byte of a look-up›table  is the number of entries in the›table,  and  the  second  byte  is the›length  of  the  entries in the table.›Each   entry   is  stored  as  a  text›string(with  no  length  byte)  and is›right  justified  in  the  table  with›underline   characters(ASCII   95)  as›filler on the left.››CONDITIONALS››     Conditional    entries    are   a›combination  of  formula  entries  and›table  look-up  entries.   The special›offset  for  a  2 entry look-up table.›Immediately  after  the  look-up table›data  is  the  formula  data  for  the›conditional field.››     The  last  thing in the .TBL file›are  two  numeric entries.  Each entry›is  16  bits  long(2 bytes, stored low›byte,  high byte).  The first entry is›the  field  count, the second entry is›the total record length in bytes.  The›record  length is one greater than the›sum of the field data lengths.››THE .CNF FILE››     The   .CNF  file  contains  eight›entries.  Each entry is 16 bits long(2›bytes,  stored  low  byte, high byte).›The entries are:››  1   The  length  of  the index array›entries›  2   the  total  number of records in›the datafile›  3   the  number of data disks in the›datafile›  4   the  number of active records in›the datafile›  5  the current record number›  6  the number of index fields›  7   the current value of the counter›field›  8               the             sort›direction(ascending/descending flag)››THE .IDX FILE››     The   length  of  the  .IDX  file›varies   with   the  total  number  of›records in the file, and the length of›the   current   index.    (Both  these›numbers  are  in  the .CNF file).  The›first  32  bytes  of the .IDX file are›the current index field.  There are 16›two-byte  entries,  the  first byte of›each  entry  is  the field number, the›second is the length of the index data›for  that  index  entry.   Any unusued›entries have undefined values, usually›0.›› *************************************›