How to understand the Command Line

Understanding the Command Line of CAD is important and it’ll help us improve efficiency and save our time.

There are prompts in the Command Line every time we execute a command. Some prompts are simple while others are relatively complex, but they all have the same format. Let me explain this in detail.

Some prompts don’t have any options, for example:

Specify the start point:

Select an object:

For such prompts, we could do as the prompts say: enter the coordinates or specify points with cursor when the prompt asks us to specify points; when the prompt asks us to select an object, we can use point selection and window selection to select the object.

Some prompts are complex and consist of text and many options, but their basic content include three parts: text, options (selectable), default option (selectable), for example:

XXXXXX or [XXX(X)/XXX(X)/XXX(X)/XXX(X)]:

[] What’s inside the square brackets are options that can be set, () what’s inside the parentheses is the keyword for the option and using the keyword can execute the option. <> what’s inside the angle brackets are default options or parameter values and we can execute the option or adopt the parameter values by pressing Enter.

We take the COPY command as an example, the prompts indicate us to select the object that we want to copy and press Enter and after all this, the following options will pop up.

The option currently being executed is “Specify base point” and we can enter the coordinates or select a point in the drawing with the cursor. There are two options inside the square brackets: Displacement(D) and Mode (O), we can execute these options by entering the keyword. But since the default option here is Displacement, we don’t need to enter “D” if we need to use the Displacement, instead, we can just press Enter.

Many CAD learners learn CAD commands according to the tutorials without knowing the reason. For example, tutorials for the Trim command (TR) would usually introduce this command like the following:

Enter TR, press Enter, press Enter and then select the object that you want to trim.

Many would ask: why press Enter twice when you could easily press Enter just once?

If you pay attention to the Command Line, you’ll know why you need to press Enter twice, the Command Line prompts for the Trim command is as following.

We execute the command by pressing Enter. After executing the command, we are prompted to select a line as a boundary line for trimming. There are two options in selecting the boundary line: by directly selecting the object or by selecting all(select all objects to trim). The former is the first option set by CAD while the latter is the default option and can be executed by pressing Enter.

Selecting all the objects as a boundary for the trim will increase the calculated amount and we might wait longer using this operation in the early versions of CAD. Many people still use this operation because it saves people trouble to select objects. I suggest selecting one to two boundary objects to get faster experience even if you’re using a higher version of CAD with better performance.

Newbies need to learn to read the Command Line, it helps us better understand the command and we can get parameter values and options from it. Try as much parameter values of other commands as possible and choose the best method for different situations.