{Program}
PROGRAM Pointers(Input, Output, InFile);
{
COMPILER      : BORLAND Turbo Pascal 7
AUTHOR        : Dale R. Palmer
DATE          : Saterday 13 April 1996
STUDENT No    : 3009-530-1
COURSE CODE   : COS211-Y
ASSIGNMENT No : 01
QUESTION No   : 01
OBJECTIVE     : Read information from an existing text file and
                store the information in a singly linked list.
                Sort, delete from and print the list as per
                the requirement of the quuestion.
PRE-CONDITION : A text file containing the required data exists.
POST-CONDITION: The list has been sorted, printed and the required
                elements have been deleted and the list has been
                reprinted.
EXTERNAL FILES: "STUDTREC.DAT" This file contains the data for the
                student records that are to be manipulated.

VAR
List   : PtrType; {Points to start of list}
InFile : Text;

{===================================================================}
PROCEDURE InsertEntry (VAR List :PtrType);
{Inserts the record into the correct position in the list.}

BEGIN

END; {PROCEDURE InsertEntry}

{===================================================================}
PROCEDURE AddList (VAR List :PtrType;
                   VAR InFile : Text );
{Reads the information for each student, calls a procedure
that inserts the new entry in the correct (sorted) position
in the list, and calculates the total number of credits.}
VAR
  NewNode   : PtrType;
  Ch        : Char;
  Index     : Integer;
  TempNum   : STRING[5];
  TempMk1,
  TempMk2,
  TempMk3,
  TempMk4   : STRING[4];

BEGIN
      New(NewNode);
      IF (List = NIL) THEN List := NewNode;
      FOR Index := 1 TO 5 DO {Read in student no.}
      BEGIN                  {Size = 5}
        Read(InFile,Ch);
        IF (Ord(Ch) >= 48) AND (Ord(Ch) <= 57) THEN
          TempNum[Index] := Ch;
      END;
      WriteLn(TempNum:5);
      WriteLn('TempNum');
      ReadLn;
      FOR Index := 6 TO 30 DO {Read in student name.}
      BEGIN                   {Size = 25}
        Read(InFile,Ch);
        {NewNode^.Name:=}
      END;
      FOR Index := 31 TO 38 DO {Read in course code.}
      BEGIN                    {Size = 8}
        Read(InFile,Ch);
      END;
      FOR Index := 39 TO 42 DO {Read in 1st mark.}
      BEGIN                    {Size = 4}
        Read(InFile,Ch);
      END;
      FOR Index := 43 TO 46 DO {Read in 2nd mark.}
      BEGIN                    {Size = 4}
        Read(InFile,Ch);
      END;
      FOR Index := 47 TO 50 DO {Read in 3rd mark.}
      BEGIN                    {Size = 4}
        Read(InFile,Ch);
      END;
      FOR Index := 51 TO 54 DO {Read in 4th mark.}
      BEGIN                    {Size = 3}
        Read(InFile,Ch);
      END;

  {InsertEntry(List);}

END; {PROCEDURE AddList}
{===================================================================}
PROCEDURE Delete (VAR List : PtrType);
{Deletes all the entries of students who failed to obtain
admission to the examination.}

BEGIN

END; {PROCEDURE Delete}
{====================================================================}
PROCEDURE PrintList (List : PtrType);
{Prints the contents of the list.}

BEGIN

END; {PROCEDURE PrintList}
{====================================================================}
BEGIN {MAIN}
  List := NIL;

  Assign(InFile,'C:\TP\PROGRAMS\STUDTREC.DAT');
  Reset(InFile);
  WHILE (NOT Eof(InFile)) DO
    BEGIN
    WHILE (NOT EoLn(InFile)) DO
      BEGIN
      AddList(List, InFile);
      END; {EoLn}
      ReadLn(InFile);
      WriteLn;
    END; {Eof}
  Close(InFile);

PROCEDURE AddList (VAR List :PtrType;

    TempNum := '';
    FOR Index := 1 TO 5 DO {Read in student no.}
    BEGIN                  {Size = 5}
       Read(InFile,Ch);
       IF (Ord(Ch) >= 48) AND (Ord(Ch) <= 57) THEN Begin
          Inc(TempNum[0]);
          TempNum[ Ord(TempNum[0]) ] := Ch;
       End;
    END;

Now that you have an answer to what happened to TempNum, I'd like
to show you a different way of reading columnar text data.  TP/BP
will allow us to access a 1-Based array of character, whose size is
not greater than 255 Chars, as if it were a string.  So, we define
a string to make it easy to read lines from the file and define
fields on top of it as array[1..n] of Char to make it easy to
access the data.  To define a data overlay of this type we simply
use a variant record.

TYPE
   tTextRecord = RECORD
   Case Integer of
      1: (Line: String;                  { Could be String[55]   }
      2: (Len   : Byte;                  { String length         }
          Number: Array[1.. 5] of Char;  { First five characters }
          Name  : Array[1..25] of Char;  { Next 25 characters    }
          Code  : Array[1.. 8] of Char;
          Credit: Array[1.. 4] of Array[1..4] of Char;
      );
   END;

Remember that the string must be long enough to contain all the
fields.  If it is longer it simply wastes data space, but that
is usually no big thing, especially if it is a local variable.

The following fragment shows how it all fits together.

VAR NewNode: PtrType;
    Rec: tTextRecord;
    err: Integer;

BEGIN
    New(NewNode);
    Readln(InFile, Rec.Line);
    Val(Rec.Number, NewNode^.Number, err);
    If Err <> 0 Then
       {-- what do you want to do if it's not a number? --};

    NewNode^.Name := Rec.Name;

    ... etc.

END;

If you are afraid of reading a "short" line, you might fill Rec
with zeros or spaces before reading the line.  That way fields
beyond the actual length of the line that was read will be nul or
space filled.  (example:  FillChar(Rec, Sizeof(Rec), 0); )

I notice that your AddList procedure automatically inserts the
first node into the list (e,g If List = NIL Then List := NewNode).  
I know of two ways to "ground" a linked list.  One is to use a NIL
pointer (e.g if Next = NIL Then {node is last node}), the other is
to have the node point back to the first node (e.g. if Next = List
Then {node is last node}).  Just thought I'd mention it so you
don't create yourself more heartache.

                      ...red