# Fortran關係運算子

== .eq. 檢查兩個運算元的值相等與否，如果是，則條件變為真。 (A == B) i不為 true.
/= .ne. 檢查，兩個運算元的值相等與否，如果值不相等，則條件變為真。 (A != B) 為 true.
> .gt. 檢查，左運算元的值大於右運算元的值，如果是的話那麼條件為真。 (A > B)不為true.
< .lt. 檢查，左運算元的值是否小於右運算元的值，如果是的話那麼條件為真。 (A < B) 是 true.
>= .ge. 檢查，左邊的運算元的值是否大於或等於右運算元的值，如果是，則條件變為真。 (A >= B) 不為 true.
<= .le. 檢查，左邊的運算元的值是否小於或等於右運算元的值，如果是，則條件變為真。 (A <= B) 為 true.

```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```

```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```