4   Basics

QCad can open more than one document. Use the menu "Documents" to switch between the different loaded documents.

You can undo most functions of QCad. There are at least 200 undo steps available. Due to this, QCad can slow-down if you've had a giant amount of objects and delete them. You can free the undo memory to get the maximum performance by saving the drawing.

QCad uses the mouse for most operations. For the beginner it's important to know that the right mouse button is used for going back one step in the construction or manipulation process. When no process is active, the right mouse button is used for going back to the last toolbar menu.

QCad supports at least 200 undo steps. This means you can take back the last 200 actions you've made with the drawing. However, if you save the drawing, the undo information gets deleted. For that reason I recommend to work with different drawing versions. Whenever your drawing reaches a usable state or you decide to make major changes on the drawing, save the drawing under a new name. This way you can go back to a previous version when something goes wrong with the new manipulations.

To work with layers can save you a lot of time. I recommend to use different layers at least for the contours, dimensionings, auxiliary objects and the border of the drawing. Objets on the same layer can get modified together as the selecting of a whole layer is much easier than selecting all the single objects on it. Please refer also to the chapter Working With Layers for more information.

There are two different zero points in QCad: The absolute and the relative zero point. The bigger one is the absolute zero point. It stays at the same place unless you move it using the editing function. The relative zero point moves always to the last used construction or reference point. This can be very useful - imagine that you want to draw a line from point (70/60) with an angle of 30° and a length of 50. To do this, you can click or type the first point and then choose the angular positioning function, activate the relative mode and type the angle (30) and the distance (50). During the whole procedure there's no need to move the relative zero manually as it moves to the first point of the line as soon as you've defined it.

Another very important feature of a CAD system are the snapping functions. If you want to draw a line from the endpoint of an arc to a grid point, you can simply activate the desired snap function an then click somewhere in the region where the point you want to catch is. A small red circle shows you the exact position of the point while you're moving the mouse cursor. Due to the inaccuracy of computer monitors, drawings may look incorrect, but if you've used snapping functions you can be sure that it is correct. The snapping functions are documented in chapter Snapping Functions.

There are many input fields in QCad which expect values. You can type plain values in them like "1.25" or as well mathematical expressions like "2.5/2" or "sin(15)*4". The expression parser also recognizes "pi" and "e" as constants.

In other input fields you can type any string you like (for example if you construct a text or specify the label for a dimension object). In these text boxes you can also enter special characters by using the following key combinations:

Character	Key Combination
° (Degree)	Ctrl + Shift + D
ø (Diameter)	Ctrl + Shift + O
µ (Mycro)	Ctrl + Shift + U
± (Plus/minus)	Ctrl + Shift + "+"
÷ (Division)	Ctrl + Shift + ":"

The internal clipboard of QCad can be used to transfer parts of a drawing to another one. Please note that it's currently impossible to exchange data with other programs over the clipboard.

For copying objects to the clipboard you need to choose the "Copy" function from menu "Edit", select the objects (Selecting Objects) and choose a reference point. If you insert the objects later in the same or in a different drawing, you can set the position using the snapping functions (Snapping Functions).

QCad uses the DXF file format for saving the drawings. I've tried to stay as close to the standard as possible. If you have a program which can not read the DXF files produced with QCad or which produces DXF files which are unreadable with QCad, please contact me. There are too many program out there for me to test them all. If problems occur with texts, you may also try to convert the texts into elements before producing the DXF.