CODEWITHSUNDEEP
delphisearchpascal
Chunky1318
Chunky1318

Reputation: 113

searching an unindexed File-of-Record in pascal (Delphi 7)

Im creating a console app for a friend using Pascal on Delphi 7. Ive sorted adding a record and viewing them, but Im having problems in searching them. The records are stored in a .dat file. Any help would be great!

Thanks!

my code so far...

Type
  BookRecord = Record
    Number : Integer;
    Title  : String[50];
    Author : String[50];
    ISBN   : String[13];
  end;

Var
  Book : BookRecord;
  f    : file of BookRecord ;   

Procedure Add_Book;
Var
  Title, Author, ISBN : String;
  i : integer;
Begin
  Assign (f, 'Books.dat');
  reset (f);
  Seek (f, filesize(f));
  Book.Number := (filepos(f)+1);
  Write  ('Title:  ');
  Readln (Title);
  For i := 1 to Length(Title) do
    Title[i] := UpCase(Title[i]);
  Book.Title := Title;
  Write  ('Author: ');
  Readln (Author);
  For i := 1 to Length(Author) do
    Author[i] := UpCase(Author[i]);
  Book.Author := Author;
  Write  ('ISBN:   ');
  readln (ISBN);
  For i := 1 to Length(ISBN) do
    ISBN[i] := UpCase(ISBN[i]);
  Book.ISBN := ISBN;
  write (f, Book);
  Close (f);
End;

Procedure Show_All;
Begin
  Assign (f, 'Books.dat');
  Reset (f);
  while FilePos(f) <> FileSize(f) do
  Begin
    Read (f,book);
    Writeln ('File:   ' , Book.Number);
    Writeln ('Title:  ' , Book.Title);
    Writeln ('Author: ' , Book.Author);
    Writeln ('ISBN:   ' , Book.ISBN);
    Writeln;
  end;
  Writeln; Writeln;
  Center ('END OF FILE!');
  readln;
  Close (f);
end;

Procedure Delete_All;
Begin
  Assign (f, 'Books.Dat');
  Reset (f);
  Seek (f,0);
  Truncate (f);
  Close (f);
end;

Thats basically my code so far... The Add_Book, Show_All and Delete_All Procs work great, but once Ive added some records how would I go about searching for an author?

Upvotes: 1

Views: 1475

Answers (1)

David Heffernan
David Heffernan

Reputation: 613461

Since your records don't appear to be sorted by author you need to use linear search. Adapt your Show_All routine to achieve this, iterating through each record looking for the author.

If you have a large database then performance will be a problem and you should consider using a real database.

Upvotes: 2

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