Read / write different Records data from / to Untyped files in Pascal? - binaryfiles

Question

I've a programming project in my college.
Using a File type for storing data is allowed, and I did exactly like this one: pascal-programming
And, here's what I achieved so far:
I tried to write the Records data into Untyped files instead and it worked
I want to override a function with dynamic parameter (e.g: I can switch which Record I want to process, in this case there's 2 different "Records").
Open(var f: File; var data)
data = represent can receive "anything". cmiiw
The reason why I did this, I don't think it's a good idea to recreate the same function over and over, e.g: when using 3 or more different "Records"
I also encountered a problem that the files can't store or backup the actual binary files to the temporary "Records" variable, it always give the 0 values.
go to my github source code
my solution here doesn't provide any generic related procedures (check the last sentences):
program test_untyped;
{ A crude database recording }
uses crt;
type
Temployee = record
name : string[20];
address : string[40];
phone : string[15];
age : byte;
salary : longint;
end;
arr_employee = array[1..100] of Temployee;
var
F : File;
c : char;
// r : Temployee;
r, realR : arr_employee;
s : string;
i, j, n : integer;
procedure fRead;
begin
seek(F, 0);
i := 0;
repeat
clrscr;
inc(i);
writeln('increment: ', i); readln;
writeln('File position : ',filepos(F));
blockRead(F, r[i], sizeOf(Temployee));
writeln('Name = ', r[i].name); { Input data }
writeln('Address = ', r[i].address);
writeln('Phone = ', r[i].phone);
writeln('Age = ', r[i].age);
writeln('Salary = ', r[i].salary);
write('Show data again (Y/N) ?');
repeat
c:=upcase(readkey); { Ask user : Input again or not }
until c in ['Y','N'];
writeln(c);
// realR[i] := r[i]; // backup, to show later
until c='N';
end; // end fRead
procedure fWrite;
begin
seek(F, filesize(F));
repeat
clrscr;
inc(i);
writeln('berapa nilai i: ', i);
writeln('File position : ',filepos(F));
write('Name = '); readln(r[i].name); { Input data }
write('Address = '); readln(r[i].address);
write('Phone = '); readln(r[i].phone);
write('Age = '); readln(r[i].age);
write('Salary = '); readln(r[i].salary);
blockWrite(F, r[i], sizeOf(Temployee)); { Write data to file }
write('Input data again (Y/N) ?');
repeat
c:=upcase(readkey); { Ask user : Input again or not }
until c in ['Y','N'];
writeln(c);
until c='N';
end;
// procedure fDelete;
// var
// nama: string;
// delElement: integer;
// tempR: Temployee;
// begin
// seek(F, 0);
// write('search your data by name: '); readln(nama);
// while not eof(F) do
// begin
// writeln('file position: ', filePos(F));
// blockRead(F, tempR, sizeOf(Temployee));
// if (nama = tempR.name) then
// begin
// delElement := filePos(F);
// end else
// begin
// // seek(F, )
// blockWrite(F, tempR, sizeOf(Temployee));
// end;
// end;
// end; // end fDelete
procedure fDisplay;
begin
writeln('nilai i saat ini: ', i); readln;
for j := 1 to i do
begin
clrscr;
writeln('Name = ', r[j].name); { Input data }
writeln('Address = ', r[j].address);
writeln('Phone = ', r[j].phone);
writeln('Age = ', r[j].age);
writeln('Salary = ', r[j].salary);
readln;
end;
end;
begin
clrscr;
// write('Input file name to record databases : '); readln(s);
s := 'coba1.dat';
assign(F,s); { Associate it }
{$I-}
reset(F, sizeOf(Temployee)); { First, open it }
{$I+}
n:=IOResult;
if n<>0 then { If it's doesn't exist then }
begin
{$I-}
rewrite(F, sizeOf(Temployee)); { Create it }
{$I+}
n:=IOResult;
if n<>0 then
begin
writeln('Error creating file !'); halt;
end;
end
else
begin { If it exists then }
n:=filesize(F); { Calculate total record }
// seek(F,n); { Move file pointer PAST the last record }
end;
fileMode := 2;
reset(F, sizeOf(Temployee));
fRead;
fWrite;
// fDelete;
fDisplay;
close(F);
end.
I'm wondering is the Pascal can be any good to use a generic programming? at least for this semester using Pascal in my college XD
Thank you and Best Regards,
EDIT:
Pascal still doesn't support Generic Programming 'till the day I posted this question. So sad, really.
You might wanna consider read this references instead.

Answer 1

I don't understand the main issue here, but would suggest using a typed file instead of an untyped one.
An untyped file is much harder to maintain, and provides (in my eyes) no benefits.
Consider the code:
type
Temployee = record
name : string[20];
address : string[40];
phone : string[15];
age : byte;
salary : longint;
end;
VAR
fEmployee : File Of Temployee;
Employees : ARRAY[0..100] Of Temployee;
Employee : Temployee;
PROCEDURE OpenEmployeeFile(CONST TheFileName:AnsiString);
BEGIN
AssignFile(fEmployee,TheFileName);
IF FileExistsUTF8(TheFileName) { *Converted from FileExists* }
THEN Reset(fEmployee)
ELSE Rewrite(fEmployee);
END;
PROCEDURE CloseEmployeeFile;
BEGIN
Close(fEmployee);
END;
FUNCTION ReadEmployee(Position:WORD): Temployee;
BEGIN
Seek(fEmployee,Position);
Read(fEmployee,Result);
END;
PROCEDURE WriteEmployee(CONST Employee:Temployee; Position:WORD);
BEGIN
Seek(fEmployee,Position);
Write(fEmployee,Employee);
END;
Error handling not implemented.
Code samples as a guideline, not complete.
It provides a basic skeleton for opening and closing the employee-file, as well as reading and writing at specific positions (specific records) in the file.
Open file.
Write all the records you want.
Close file.
Or.
Open file.
Read all the records you want.
Close file.