>I want to read the text file contents from bottom to top line by line and simultaneously delete the line from bottom top line by line.

Ravi,

Assume lines are sepatared by CRLF, or only by CR or LF.

lcOldText = FileToStr('filename')
lnCR = RAT(CHR(13),lcOldText)
lnLF = RAT(CHR(10),lcOldText)
IF lnLF - lnCR = 1
  * LAst separator is a CRLF or only a LF in position 1
  lcLastLine = SUBSTR(lcOldText,lnLF+1)
  lcNewText = LEFT(lcOldText,lnCR-1)
ELSE
  * Last separator is a lone CR or LF
  lcLastLine = SUBSTR(lcOldText,MAX(lnCR,lnLF)+1)
  lcNewText = LEFT(lcOldText,MAX(lnCR,lnLF)-1))
ENDIF
StrToFile(lcNewText,'filename')

Alex