one line if statement
program ifmain
real x
x=3
if (x.lt.10) write(*,*) 'x is less than 10'
stop
end
if true, then a block of code
program ifmain
real sum
sum=0
x=9
if (x.lt.10) then
sum=sum+x
x=x-1
endif
stop
end
if block1, else block 2
program ifmain
x=9
if (x.lt.10) then
x=x+1
else
x=x-1
endif
stop
end
single selection from multiple choices, simulate switch statement
program ifmain
integer choice
choice=3
if (choice.eq.1) then
write(*,*) 'choice 1'
elseif (choice.eq.2) then
write(*,*) 'choice 2'
elseif (choice.eq.3) then
write(*,*) 'choice 3'
else
write(*,*) 'choice beyond 1 to 4'
endif
stop
end