You need to install any of the tamil unicode font to read or write tamil , commonly used unicode tamil font is AnjaliOldLipi True Type Font . Please following the instructions to install unicode tamil in your system.
There was no common tamil ascii structure for the old fonts. so each vendors use different tamil fonts with different keyboard layouts. this makes difficult with tamil users as they need to install each tamil font from different websites like malayala manoram (manoram.ttf) mathrubhumi.ttf etc..
Unicode font is international