How do you make symbols by command in autocad?

Friend your question need very long reply,

Name

Control Codes

Unicode Strings

Degree (°)

%%d

U+00B0

Plus/Minus Tolerance (±)

%%p

U+00B1

Diameter ()

%%c

U+2205

Text symbols and Unicode strings

Name

Symbol

Unicode String

Almost equal

U+2248

Angle

U+2220

Boundary line

U+E100

Centerline

U+2104

Delta

U+0394

Electrical phase

U+0278

Flow line

U+E101

Identity

U+2261

Initial length

U+E200

Monument line

U+E102

Not equal

U+2260

Ohm

U+2126

Omega

U+03A9

Plate/property line

U+214A

Subscript 2

U+2082

Squared

U+00B2

Cubed

U+00B3

check this & u can found more list at autodesk.com

Waiting for expert answer. Thank you 

I've a block library that I use also you can search the the web for blocks

Make symbols as blocks (for eg: Door) --> when you want to insert just type DOOR in command bar  (make sure to turn off dynamic input)

sorry i'm not expert on Autocad Program

In the place of text editor, right click and add symbol

copy and paste

in text formatting tool bar click symbol

shift+%% ,shift + c ,Shift + D, 

Agree with the previous answers

Thanks