Actually, i am using old MMC with 64 mb.so, it does not have lock tab.
I've also copied T_READ.txt and T_WRITE.txt before running the sketch.
But oh!!! I see ,I created new blank T_WRITE.txt with one character in MMC but didn't copy the provided blank T_WRITE.txt in example folder with 2KB size. Above link enlists one of the restriction as "cannot expand file size". so is it due to this restriction that i am able to write only one character?
Do we need to first define the size of file to be written?