Win32 Console Applications - Part 1.
Okay, hands up, who here started out with something like this, possibly in another language, possibly on another OS, but whatever, with something like that. I'm willing to bet there are a good few people who can say "yes, that was me". You don't really want to see the source do you? Oh all right then.
#include <iostream>
using namespace std;
int main()
{
cout << "Hello World!" << endl;
return 0;
}
8 lines. Could be less, by why make things harder to read? This is really the great strength of a Windows Console Application, you really do not need to do much in order to make a working program. That is why I use consoles. If I want to test out a bit of non GUI code, and I don't have a suitable application I can use as a framework, I knock together a quick console application, and I'm sure just about every other Windows programmer does as well. The user interface only needs to be sophisticated enough to get the job done.
Some of the other tutorials on the site demostrate powerful techniques, but do it in a Console App because that's all that was needed.
Can you do anything else with a Console App? Of course, the answer is yes, you can, and these tutorials demostrate some of the things that can be done with a console. Believe it or not, a huge number of questions concerning consoles crop up in help forums every week, so people are interested. If you are, read on.
What is a Console? It is a Window, a special kind, yes, but it is a Window. You will frequently hear these things called "DOS boxes" because DOS had a character based UI, but this term is incorrect. There is no DOS under the NT cored WIndows operating systems, (NT, 2000, XP), and yet you can use a console. Why? Because it is a Window. (There are actually DOS emulators for these platforms - but this is a totally unrelated topic.)
What makes a Console window special is that it is character based rather than pixel based. A normal window, like this browser window for example, (unless you're using a REALLY basic browser), is measured in pixels, each pixel is individually addressable and modifiable. With a character based medium, that is not the case, the smallest unit that can be addressed and thus modified is a character cell.
A console's display area consist of rows and columns of character cells. It is a grid or two dimensional array or matrix of cells, all these terms are in use - they amount ot the same thing. Traditionally, the character cell at the top left is the origin or "home" position, and is designated (0,0) in an imaginary (x,y) grid. The character cell to it's immediate right is (1,0), the next (2,0) and so on. The cell just below (0,0) is (0,1), the one below that (0,2) and so on. On a typical console there are 80 cell positions across the screen, and 25 down, thus on such a console, the bottom right cell will be (79,24) remembering the grid is zero based. The little picture below shows graphically the cell numbers of the upper left portion of a larger screen or the entire grid of a 4x4 console of course.
Incidently, the reason for chosing 80x25 is historical. In the days before graphical terminals were widely available, people used character based terminals called "Visual Display Units", or VDU's. These typically had an 80x25 screen layout. I was one of those who used these beasts.
Each character cell can contain one and only one character. I'll illustrate an artifact of this below. I type 5 "w" characters, then on the line below, 5 "i" characters...
wwwww
iiiii
... notice the length of the lines. Assuming you are using a modern browser, you should see that the upper line is longer than the lower. Now I'll write a console app which does the same, here is the output...
... as you see, since each cell can only hold a single character, the last "i" character is directly below the last "w". There can be no proportional spacing in a console with the default font, (it is possible to simulate a very crude form of proportional spacing if only a few letters are used - but forget it - it's not worth the hassle).
Okay, so we've got a grid of cells, what is in a cell? Simply, a cell is another grid, each cell being 8 pixels wide and 12 high. The characters that make up the font must be represented within this grid including any spacing - that's right, the pixels of one cell lie directly adjacent to the pixels of the next. This is somewhat limiting, and accounts for the rather poor quality of the console font, but as we will see later, it does have some advantages. The pictures below show how the "w" and "i" characters are encoded into a cell.
Notice the blank column on the right of the "w", this ensures that two adjacent "w" characters will have at least a single pixel space between them. If you look at the last picture, you will see that is the case. Also notice, the dot over the "i" does not go to the top of the cell, this ensures that any character on the line above an "i" that has a descender, an extension below the normal line, "y" for example, will still have at least a one pixel gap between the descender and a "high" character. Thus, normal characters are represented by 7x11 grids with a blank row at the top and a blank column on the right side.
The pixels marked with a "X" in the pictures above are rendered in the foreground colour, those in the empty pixels positions, in the background colour. By default, the foreground is white, the background black. Later on in the tutorial, I will show you how to change these colours, within limits.
There is a one pixel wide gap around the outside edge of the consoles display area. This prevents the top, bottom and edge characters merging with the frame. You cannot write into this gap. Thus a console's display area is 2+(8x) pixels wide, where x is the number of character cells in a row, and 2+(12y) pixels high where y is the number of visible rows, (there may be more rows above or below the current view as determined by the position of the scroll bar).
I'm afraid this first page has really been rather a lot of dry theory. A lot of what you can do with consoles assumes you understand this material though, so read it through, and if later on in this tutorial, you find something that sounds weird, try reading this page again!
In the next part, I'll show you how to name your Console, obtain the consoles standard handles, move the cursor about, write blocks of characters and clear the screen.