What?
When you press any number or the equal to sign or the front-slash charcater the F10 key you will find a yellow input box popping up

This is the Headsup Command Line (also sometimes referred as the yellow command line due to its color)

This can be used to directly send some of the commands by typing them out into the input box instead of clicking on a menu/button

One important use of this command line is to give accurate instructions to move the architect precisely, as per dimensions. See examples given below. But there are many other uses of this command line too, as explained here

Creating objects
If the first character is an equals-to sign = then that command is used to create a new object. There are several variations of the creation command. Everything you obtain from the Create Objects dialog can be done using this feature

Changing the stepsize
If the first character is a slash, then that command is used to change the step-size (i.e. architect's size) If there is NO value whatsoever after the slash, then the step-size reverts to the previous step-size. If there is space and a value after the space, then the step-size will become that value

Of course that value MUST be a sensible number, and that too – it should not be a negative value.

Moving the architect precisely
If the first character typed in is a number, then the command you write would be treated as an instruction to precisely move the architect.

Examples:
In all the examples below [ENTER] means that you need to press the enter key when typing inside the Headup Command Line

0.5[ENTER}
Just this value of 0.5 will move the architect PRECISELY by 0.5 meters from the previous location of the architect moving in line towards the first helper

0.5 <50[ENTER]
This will move the architect 0.5 meters on a line drawn 50 degrees counter-clockwise from the first helper

3'6“[ENTER]
This will move the architect precisely 3 feet 6 inches from the previous location of the architect moving in line towards the first helper

Note that you can ALSO ask TAD to do mathematical calculations too when using the command line. Wherever you see 0.5 in the examples given earlier; you could even write 0.3+0.2 But make sure that there is NO spaces in that mathematical expression – as TAD uses the spaces to distinguish each part of what you entered.