LESSON-1:
1.1 Introduction:
First of all let’s have a look at the AutoCAD 2010 interface.
When you open it the initial workspace is at Initial Setup Workspace. You can change it to
2D Drafting & Annotation, 3D Modeling and AutoCAD Classic mode as necessary by clicking the Workspace Switching menu at lower right corner. We will proceed with 2D Drafting & Annotation for 2D drawings. In this workspace only the tools for 2D drawing are given. In 3D Modeling, all the tools for 3D drawing are given. But in Initial Setup Workspace, both the 2D & 3D drawing tools are given. So sometimes it is preferable to work in Initial Setup Workspace. In AutoCAD Classic the interface of the software from 2000-2008 are given. If anyone, who is very much habitual with the previous versions, can use this workspace for convenience instead of the new one which was adopted from 2009.
1.2 Different Parts of the Interface:
At first , at the upper left corner, you will find the Menu Browser (see the first figure). By clicking it, you will have the options to open new file, previous saved file, save option, print, publish etc. commands. You can see the recently opened documents. By clicking “Options” button, you can modify your drawing preferences. 
In the Quick Access Toolbar, there is provided the same options like new file, save, open etc. By clicking the drop down arrow, you can add or deselect commands.
In the InfoCentre, the functions are similar. The functions are search, help, action centre etc.
Below these is the ribbon. This is made of several tabs. Again the tabs are made of several panels. These panels provide tools for drawing and modification.
In the Command Palette, in the upper part, the commands just entered are shown. In the lower part, the current command is shown. You can write command here and it shows what to do next. So it is very important to always keep an eye on this command line to give the correct inputs.
In the Status bar, there are some buttons to toggle (turning on/off) some functions like snap, polar, ortho etc. which are very necessary during drawing. And in the right side there are some helping buttons like switching workspace (which you have seen previously), pan, zoom, steering wheel, quick view layout, clear screen etc. the ribbons at right and left side of the interface are docked panels.
1.3 Input System:
Everything drawn on AutoCAD are drawn at accurate scale. The drawings are placed on the sheet by co-ordinate system. In 2D, it is two axis -X,Y co-ordinate system and in 3D it is three axis- X,Y,Z co-ordinate system. You can see it while moving the cursor (which is actually called Cross Hair in AutoCAD) in the workspace, at the lower left corner the co-ordinates are shown simultaneously.
The default co-ordinate system is called WCS (World Co-ordinate System). Everything you draw, are drawn in WCS. Sometimes designers need to change the default co-ordinate system for drawing purpose. That is called UCS (User Co-ordinate System).
So, when you are drawing a line 10 units long, the inputs should be (0,0) and (8,0) for horizontal length; or (0,0) and (0,8) for vertical length (The commands for line, circle, rectangle etc. are coming next. This is just to give the conception of using co-ordinate system).
Now, the points you enter are the absolute points. If you need to put any point with respect to the entered last point, then you have to write the symbol “@” before the co-ordinate of the desired point. This point then will be called the relative point.
Those were all linear inputs. But sometimes you have to draw angular lines. In that case you have to mention the angle. In AutoCAD angle is measured counterclockwise. The 0 degree starts from 3 o’clock, then increases counterclockwise.
For example, you have a line and need to draw another line at the left point at 450 angle (Fig. 1). Now from the left point, upside the line, if you start measuring angle , it goes counterclockwise. So simply give the angle value 450. But if you have to draw the line from the right corner, the measurement goes clockwise. So you have to imagine it counterclockwise, then value should be 900+450= 1350 .
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