(1) If then x is called logarithm of y to the base a. it is written as

(2) if the base of the Logarithm is taken as 10, it is known as common Logarithm.

(3) If the base is taken as e (approximately 2.718) then it is known as natural or Naperian logarithm.

(4) the integral part of the common Logarithm of a real n umber is called the characteristic and the decimal part of the mantissa.

(4) For the number greater than 1, the characteristic of the Logarithm is equal to the number of digit in the integral part of the number minus 1 (mean short one).

(5) When a number is less than 1 mean < 1 or in negative, the characteristic is always written as

(instead of -3, -2 -1) to avoid the mantissa becoming negative.

(6) The Logarithm of real number s having the same sequence of significant digit have the same mantissa.

(7) The real number corresponding to a given logarithm is known as antilogarithm.