The American Standard Code for Information Interchange, abbreviated as ASCII, is a binary code representing characters in most computers. The basic ASCII set includes letters of the English alphabet as well as other symbols and characters, including triangles. You have to use a specific numeric code to type and insert an ASCII symbol into a document. So while the specific character is not a key on your keyboard, you can create the triangle with a keyboard combination.
Open an editor program or a document in which you need to install the triangle symbol. In Windows, for example, click the "Start" button, select "All Programs," choose "Accessories" and click "Notepad."
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Press the" NumLk" on your keyboard, making sure the Num Lock option is on.
Press and hold the "Alt" key.
Type "30" or "31" on the numeric keypad. It should generate "triangle up" or "triangle down" symbols.
Release the "Alt" key to insert the triangle symbol.
You must use the numeric keypad on the right side of the keyboard to type the numbers in Step 4.