### variable.f

c23456
program var1
integer sum
real rad,degree
double precision d1,d2
complex com
logical f
character c
parameter(pi=3.14, half=180)
c integer type if a variable name start with character between i and n
i=1
j=2
k=3
l=4
m=5
n=6
a=3.14 !otherwise it is real
sum=i+j+k+l+m+n
rad=a
degree=half*rad/pi
write(*,*) 'sum=',sum
write(*,*) 'degree=',degree
stop
end

### Output

sum= 21
degree= 180.00000

a fortran variable name are not case sensitive. The first character must be a letter [a-z], and the following character could be letter or digit [a-z0-9]

if not explicitly declared, a variable name start with a character i,j,k,l,m,n are of integer type. If not started with those character, then the type is real