why we are using only .txt files to upload files in LSMW??

Hi Experts,

When we are using LSMW,for uploading files we are using file in .txt format,is there any other format we can upload the files in LSMW??

If we are using only .txt files can any one tell me why we are using only .txt files to upload files in LSMW??

Thanks and Regards,

Sunil Boya