2Bytesprog2 course_2014_c3_txtfiles

Prog_2 course- 2014
2 bytes team
Kinan keshkeh
IT Engineering-Damascus University
3rd year

Files
TxT Files
char(ACII)
Binary File
0/1

Who can tell me from where we read and write in our normal program?
In Files: Keyboard file Screen file
Why files? To save things..(whereas in normal way we cant save things after program end).. Then we can read|| write from it !
NOTE: First of all.. We have to know that each file has Pointer at the Begin of file and Pointer at the End of it -The end of line determined by (Enter) #13

There is :
Physical name ( koko.txt /koko.bin)
logical name (f:txt / f:file of _sth_)
File :
read
write
Note: Attention !! The most important thing is the method we read and write files
modification
has its arrangement(use another file to help )

The Definition
At main Program:
Var f :Text;
At procedures/functions:
procedure ___(…Var f :txt)
We use “Assign” to link physical name with logical name: Assign(f,<filename>)
-If the file at (Bin)(the same folder of pascal) : you don‟t have to write whole direction Ex:(Assign(f,‟soso.txt‟) ) -else you have to write whole direction Ex:(Assign(f ,‟D:fififofo….soso.txt‟) )

The Definition
At main Program:
Var f :TXT;
At procedures/functions:
procedure ___(…Var f :txt)
We use “Assign” to link physical name with logical name: Assign(f,<filename>)
-If the file at (Bin)(the same folder of pascal) : you don‟t have to write whole direction Ex:(Assign(f,‟soso.txt‟) ) -else you have to write whole direction Ex:(Assign(f ,‟D:fififofo….soso.txt‟) )

Read from Txtfile
Reset(f)
Read(f,c); (when you dunno how the file is created )
Readln(f,st);
Readln(f);
+1
close(f)

write from Txtfile
Rewrite(f)
write(f,c);
writeln(f,st);
writeln(f);
+1
close(f)

Notes On Reset/Rewrite:
If File exist
If File Not exist
Reset
Put the Pointer at the begin of file ..
Error
Rewrite
Erase file content
And put the Pointer at the begin of file to write
Create new file

How can we know the end of file ?? How can we do the end of line ?
Eof(f): return true when the file end.
Eoln (f): return true when the line end.

--------
EMPno EMPName SAL
100 saeed 5000
2 Eyad 25000
78
--------
------------
.
.
.
.
.
Ques: We want to write a Txt file like that below ..and read from it and print its content on Screen :

Write on file:
Program Soso;
Var filename:string[20];
f:txt; i:integer; c:char; st:string[100];
Eno:integer; Ename:string[40]; Esal:real;
Begin
readln(filename); Assign(f, filename);
Rewrite(f);
writeln(f, „EMPno‟:15,‟EMPName‟:15,‟ SAL‟:20);
writeln(f,‟----------‟,‟ -----------------‟,‟-----------‟);
for i:=1 to 100 do
begin
readln(Eno,Ename,Esal);
writeln(f,Eno,Ename,Esal);
end;
close(f);
End.

Read form file
1) (because)/if we know the structure /how it is written :
Reset(f);
Readln(f,st); Readln(f,st);
While not eof(f) do
Begin
readln(f, Eno,Ename,Esal);
writeln(Eno,Ename,Esal);
end;
Close(f);
+1

2) (because)/if we don’t know the structure /how it is written :
Reset(f);
While not eof(f) do
Begin
while not eoln(f) do
begin
read(f, c);
write(c);
end;
writeln; readln(f);
end;
Close(f);
Reset(f);
While not eof(f) do
Begin
begin
readln(f, st);
writeln(st);
end;
end;
Close(f);
Line long
You have to define the big number string

Important Example
PC Computer
We have Txtfile In English( of course :p )
-Each word ends at its line.
-Between words there is Only one Space „ ‟.
There are in this file words “Computer” .. We want replace them by ”PC”..
You have to Keep your eyes with me all..

Program ComputerToPC;
VAR
f, new: text;
ch: Char;
s: string[8];
i: integer;
flag: boolean;
Begin
assign(f,'mo.txt');
reset(f);
assign(new,'new.txt');
rewrite(new);

while not eof(f) do
begin
flag := true;
begin
if flag then
read(f, s)
else
begin
read(f, ch);
s[8] := ch;
end;
if s = 'computer' then
begin
write(new, 'PC');
flag := true;
end
else
begin
flag := false;
if eoln(f) then
write(new, s)
else
write(new, s[1]);
for i := 1 to 7 do
s[i] := s[i+1];
end;
end;
readln(f);
writeln(new);
end;
close(new);
readln;
End.{program}

When we want to open an existing text file for writing at the end of it , without removing its original contents using the procedure Append
Appending to a text file:
Program Soso;
Var filename:string[20];
f:txt; st:string[10];
Begin
readln(filename); Assign(f, filename);
Append(f);
writeln(„put what do you want at the End of file : ‟);
readln(st);
writeln(f,st);
close(f);
End.

Homework: you have a TXTfile it contains Student name/student number/prog_1 mark/prog_2 mark/ 1)put the sum of the two subjects to this file , then ensure of that. 2)print the sum of the two subjects on screen
+10 points
+7
+3

Group : group link
Mobile phone- Kinan : 0994385748
Facebook account : kinan’s account
2 bytes team

2Bytesprog2 course_2014_c3_txtfiles

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