下表列出了所有的Fortran支持的关系运算符。假设变量A=10和变量B=20，则：

操作符	等同	描述	示例
==	.eq.	检查两个操作数的值相等与否，如果是，则条件变为真。	(A == B) i不为 true.
/=	.ne.	检查，两个操作数的值相等与否，如果值不相等，则条件变为真。	(A != B) 为 true.
>	.gt.	检查，左操作数的值大于右操作数的值，如果是的话那么条件为真。	(A > B)不为true.
<	.lt.	检查，左操作数的值是否小于右操作数的值，如果是的话那么条件为真。	(A < B) 是 true.
>=	.ge.	检查，左边的操作数的值是否大于或等于右操作数的值，如果是，则条件变为真。	(A >= B) 不为 true.
<=	.le.	检查，左边的操作数的值是否小于或等于右操作数的值，如果是，则条件变为真。	(A <= B) 为 true.

示例

试试下面的例子就明白所有在Fortran语言可用的逻辑运算符：

program logicalOp

! this program checks logical operators
implicit none  

   ! variable declaration
   logical :: a, b
   
   ! assigning values 
   a = .true.   
   b = .false. 
   
   if (a .and. b) then
      print *, "Line 1 - Condition is true"
   else
      print *, "Line 1 - Condition is false"
   end if
   
   if (a .or. b) then
      print *, "Line 2 - Condition is true"
   else
      print *, "Line 2 - Condition is false"
   end if
          
   ! changing values 
   a = .false.   
   b = .true. 
   
   if (.not.(a .and. b)) then
      print *, "Line 3 - Condition is true"
   else
      print *, "Line 3 - Condition is false"
   end if
   
   if (b .neqv. a) then
      print *, "Line 4 - Condition is true"
   else
      print *, "Line 4 - Condition is false"
   end if
   
   if (b .eqv. a) then
      print *, "Line 5 - Condition is true"
   else
      print *, "Line 5 - Condition is false"
   end if
   
end program logicalOp

当编译并执行上述程序,将产生以下结果：

Line 1 - Condition is false
Line 2 - Condition is true
Line 3 - Condition is true
Line 4 - Condition is true
Line 5 - Condition is false