Hi Haytham,
The answer is in this support pagehttps://support.microsoft.com/en-us/help/78113/floating-point-arithmetic-may-give-inaccurate-results...
All computers have a maximum and a minimum number that can be handled. Because the number of bits of memory in which the number is stored is finite, it follows that the maximum or minimum number that can be stored is also finite. For Excel, the maximum number that can be stored is 1.79769313486232E+308 and the minimum positive number that can be stored is 2.2250738585072E-308.