Velthuis.Console unit

An up-to-date version of this and other files can be found in my Consoles project on GitHub.

I write a lot of console programs to test simple concepts, containing a few test routines and a few Writeln commands. To me, this is much more convenient than having to write a VCL program where the output goes to a ListBox or a Memo.

To be able to wait for any key, I wrote a simple unit with a ReadKey command, like in the old Turbo Pascal Crt unit. I added a KeyPressed command, a TextColor routine, and so the Console unit was born. Now it emulates most of the functionality of the Crt unit. The single routines, constants and variables are discussed in the tables below. Everyone familiar with the Crt unit will recognize them immediately.

I tested the unit in Delphi 5 up to Delphi 2006. It contains a few $IFDEF clauses to make it compile in all of the Win32 versions in that range.

UPDATE: I removed SysUtils from the implementation section. It turned out it was only used for the Win32Platform variable, which is queried in a few routines. I wrote my own routine to get the platform ID and so SysUtils is not needed anymore, which can considerably reduce the size of console programs. My EchoC utility was reduced by more than half its size.

Installation

Copy the contents of the zip file to a directory of your choice, and open the .dpr file in Delphi. If necessary, make sure the compilation target is Delphi Win32. Build the program, and take care that the unit is compiled or copied to a directory in the compiler’s search path (typically to $(BDS)\lib or $(DELPHI)\lib). Now you can use it from any console program you write. Note that you will have to recompile it for every Delphi version you have.

The program itself demonstrates a few of the capabilities of the unit. You are free to enhance it.

Constants and variables

The unit contains the following constants and variables.

Functions and procedures

The unit implements the following functions and procedures. Coordinates are all 1-based.

Notes

Window

On most console windows, the buffer for the console window can exceed the window, both in width and in height. That is why Window is not restricted to the screen. It can take the size of the entire buffer. This will of course require scrolling with the scroll bars, and may not be desired. That is why I supplied the functions ScreenWidth, ScreenHeight, BufferWidth and BufferHeight, to make it easy to calculate the window you want to set.

As long as a window is set that does not span the entire buffer, internal routines are used to display text, i.e. Writeln and friends will write via those routines. To reset the window to the entire buffer, you can either set Window(1, 1, BufferWidth, BufferHeight), or you can simply specify a first parameter of zero or below, e.g. Window(0, 0, 0, 0).

The internal routines will treat the characters #8 (backspace), #9 (tab), #10 (line feed), #12 (form feed) and #13 (carriage return) as special control characters. The original Crt unit does not handle #9 and #12 like that, if a window is set.

Sound, Delay, NoSound

on Windows NT, 2000 and XP, it is not so easy to turn on the internal speaker with Sound and let it run until you stop it with NoSound. Instead, I use the Windows.Beep function.

To make older example code run, I made two versions of Sound. One expects a frequency and a duration, and works like Windows.Beep. The other works more or less like in Turbo Pascal. You start by calling Sound(Frequency);. Because such calls are usually followed by a call to Delay, I actually only made Sound store the frequency and set a flag. Delay, if it sees the flag is set, now has all information to call Windows.Beep, which it does, and then resets the flag. So while it may look as if

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Sound(400);
Delay(200);
NoSound;

actually first starts the speaker, then waits for 200 milliseconds and then stops the speaker again, in fact Sound only stores the value 400, and sets the ssPending flag. The speaker is not started yet. But Delay now sees the flag, reads the value 400, and together with the duration of 200, it can call

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Windows.Beep(400, 200);

now. NoSound simply does nothing, in this case.

On Windows 95, 98 and ME, the routines directly access the ports, so Sound does actually start the speaker, Delay only waits, and NoSound turns the speaker off again.

Update: I turned the routines Sound, NoSound and Delay into procedural variables, and set these according to the OS. This way, the routines don’t have to check for the OS anymore. Only the startup of the unit will do that. I had to rename Sound(Frequency, Duration) to Beep, since procedural variables can of course not be overloaded.

TextMode

These days, I don’t think it makes much sense to define and use text modes like 80×25 Mono or 40×25 mono or colour. So currently, TextMode simply does nothing.

Legalese

The Console unit (console.zip) is freeware. All rights are reserved. Its code is provided as is, expressly without a warranty of any kind. You use it at your own risk.

I hope this code is useful to you. If you use some of it, please credit me. If you modify or improve the unit, please send me the modifications.

I may improve or enhance the unit myself, and I will try to post changes here. But this is not a promise. Please don’t request features.

Rudy Velthuis