2719:College Student Guide to Reading and Writing Files
KEYWORDS: Reading Files, Writing Files, Assign, Rewrite, write, Close AREA: Ge
College Student Crib Notes to:
1) Printing out your programs' output to a file.
2) Printing out your programs' output to the printer.
3) Reading from an input file.
Printing Out Your Programs Output to a File
-------- --- ---- -------- ------ -- - ----
Often times, professors will require more than your honesty
and good faith to receive full credit for your program. They
will want to see both your program listing and the output
generated from the program. But how do you do this in Delphi
and our Pascal Products ???
Simply in Delphi ....
program CrtApp;
uses WinCrt;
var outfile: TextFile;
begin
AssignFile(outfile, 'c:\outfile.txt');
Rewrite(outfile);
writeln(outfile, 'Hello World from Delphi');
writeln(outfile, 'My Program works, and here is ' +
'the output to prove it...');
CloseFile(outfile);
end.
Simply in Pascal .....
Program HelloWorld;
var
outfile: text;
begin
assign(outfile, 'c:\output.txt');
rewrite(outfile);
writeln(outfile, 'Hello World');
writeln(outfile, 'My Program works, and here is the
output to prove it...');
close(outfile);
end.
Printing Out Your Programs' Output to the Printer
-------- --- ---- --------- ------ -- --- -------
In some cases, there may be a need to print output directly to
the printer. This is the way.
In Delphi ...
program CrtApp;
uses WinCrt;
var outfile: TextFile;
begin
assignfile(outfile, 'LPT1');
rewrite(outfile);
writeln(outfile, 'Hello World from Delphi');
writeln(outfile, 'My Program works, and here is ' +
'the output to prove it...');
closefile(outfile);
end.
In Pascal ...
Program HelloWorld;
var
outfile: text;
begin
assign(outfile, 'LPT1');
rewrite(outfile);
writeln(outfile, 'Hello World');
writeln(outfile, 'My Program works, and here is the
output to prove it...');
close(outfile);
end.
Reading From an Input File
------- ---- -- ----- ----
Many times, it will be neccessary to read information from an
input file supplied by another person. This is an example of
how to implement this.
In Delphi ...
program CrtApp;
uses WinCrt;
var
infile, outfile: TextFile;
num_lines, x: integer;
line: string;
begin
assignfile(infile, 'C:\INFILE.TXT');
assignfile(outfile, 'C:\OUTFILE.TXT');
reset(infile); {reset moves the pointer to the beginning}
{of the file. }
rewrite(outfile); {clears the contents of the file}
readln(infile, num_lines);
for x:= 1 to num_lines do
begin
readln(infile, line);
writeln(outfile, line);
end;
closefile(infile);
closefile(outfile);
end.
In Pascal ...
Program ReadInput;
var
infile, outfile: text;
num_lines, x: integer;
line: string;
begin
assign(infile, 'C:\INFILE.TXT');
assign(outfile, 'C:\OUTFILE.TXT');
reset(infile); {reset moves the pointer to the beginning}
{of the file. }
rewrite(outfile); {clears the contents of the file}
readln(infile, num_lines);
for x:= 1 to num_lines do
begin
readln(infile, line);
writeln(outfile, line);
end;
close(infile);
close(outfile);
end.
{START INFILE.TXT}
2
Hello World
My Program works, and here is the output to prove it.
{END INFILE.TXT}
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For further reference, please check your Programmer's Reference.
Look for the topics (AssignFile, Assign, Reset, Rewrite, readln,
writeln, Close, CloseFile)
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This document was written and inspired by the author's sympathy
for the starving college student-- only because he was recently
in your shoes..!!
TI
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