Text files are disc files consisting of lines of ASCII characters. Unlike memory-based Pascal data structures,
text files are relatively permanent. Also, text files have no predefined length; they can be as long as your
disc
space permits. Text files are represented by variables of predefined type text. For example:
var MyFile
: text;
Once a little setup work has been performed, you can read a text file as easily as reading the keyboard, and
write to it as though you were writing to the screen. The same Writeln/Readln procedures are used, with the name
of the file preceding the data to output in the call. For example:
Write('Hello');
sends 'Hello' to the screen, and:
Write(MyFile, 'Hello');
sends 'Hello' to the end of text file MyFile.
The Assign procedure makes a connection between a Pascal variable of type Text and the MS-DOS file name you want
the file to have. Use the Reset procedure to prepare to read a text file; use Rewrite to create a new, empty text
file in preparation for writing to it. Call Close when you're through working with a file.
Text files are sequential; that is, they must be accessed in order. This is in contrast to typed (random-access)
files in which any part of the file can be accessed in any order.
program MakeATextFile;
var TheFile:
Text;
begin
Assign(TheFile,'ADDRESS.TXT');
Rewrite(TheFile); { create a new, empty file
and prepare to write to it }
Writeln(TheFile,'College of the South West');
Writeln(TheFile,'Timbury Street');
Writeln(TheFile,'ROMA 4455');
Close(TheFile);
end. { MakeATextFile }
program
ReadATextFile;
var
TheFile: Text;
S: String;
begin
Assign(TheFile,'ADDRESS.TXT');
Reset(TheFile); { prepare to read an existing
file }
while
not EOF(TheFile) do
begin
Readln(TheFile,S); {
read from the file }
Writeln(S); { and write to the screen }
end;
Close(TheFile);
end. { ReadATextFile }
