Loops

• The loop

    For i := begin (step) end do
       statements
  

  has the following form in FORTRAN:

        do i = begin, end, step
           statements
        end do
  

  begin, step and end must be of type integer.
  If step = 1, it may be omitted.
  Example:

        sum = 0
        do i = 1, 10
           read *, number
           sum = sum + number
        end do
  

• loop:

    while condition do
       statements
  

  has the following form in FORTRAN:

        do while ( Condition )
           statements
        end do
  

  Example:

        sum = 0
        read *, number
        do while ( number .ge. 0 )
           sum = sum + number
           read *, number
        end do
  

• if-then-else type statements the if then else construction has one of the following forms in FORTRAN:

        if ( Condition ) then
           statements
        end if
  

  or

        if ( Condition 1 ) then
           statements
        else if ( Condition 2 ) then
           statements
        else
           statements
        end if
  

  Examples:

        if ( i .eq. 0 ) then
           a = a+1
           print *, a
        end if
  

  or

        if ( i .eq. 0 ) then
           read *, a
           print *, a
        else
           read *, b
           print *, b
        end if
  

  or

        if ( i .eq. 1 ) then
           a = a+1
           print *, a
        else if ( i .eq. 2 ) then
           b = b+1
           print *, b
        else
           c = c+1
           print *, c
        end if