When personal computers were built for the first time, many characters like Latin languages (French, Portuguese), English with accent marks, symbols ($ sign, etc.), and icons (happy face, etc.) were not supported and were not associated with keys. So, IBM developed a way to display the special characters which can't be input with the keyboard on the screen. While pressing the Alt key down, type the code defined for the character via the Alt Numpad input method. Then other operating systems developed this feature or extended forms that are still available now, such as DOS and Microsoft Windows systems.
Using Alt codes method is a lot faster than searching for symbols in the library, and then inserting it. It also helps if you have a broken key. For example, you can use this code Alt+ 032 to add spaces between words.
There are hundreds of Alt key symbols. They are created by the combination of the alt key and numbers. For example, Alt+1 to Alt+31 represent icon symbols like faces and icons, numbers 176 to 223 represent graphic lines and polygons.
Alt codes consist of 5 digits.