Gaussian Elimination using Fortran

gaussian_elimination.f90

program ques_05
    implicit none
    integer, parameter :: n = 4 !No of variables
    integer :: i, j
    real :: a(n,n+1), x(n), s

    !TODO: input all coefficient in 'a6q5_in.txt'
    open(unit = 2, file = 'input.txt')

    do i = 1, n
        read(2,*)(a(i,j), j = 1, n+1)
    end do

    write(*,'(/, "Augmented Matrix is : ", /)')
    do i = 1, n
        write(*,'(4(5(f10.2,3x)))')(a(i,j), j = 1, n+1)
    end do

    do j = 1, n
        do i = j+1, n
            a(i,:) = a(i,:) - a(j,:) * a(i,j) / a(j,j)
        end do
    end do

    write(*,'(/, "After Gaussian Elimination : ", /)')
    do i = 1, n
        write(*,'(4(5(f10.2,3x)))')(a(i,j), j = 1, n+1)
    end do

    do i = n, 1, -1
        s = a(i,n+1)
        do j = i+1, n
            s = s - a(i,j) * x(j)
        end do
        x(i) = s / a(i,i)
    end do

    write(*,'(/, "X : ",2/, 4(F10.2, /))')(x(i), i = 1, n)

end program

input.txt

2 1 -1 4 19
-1 -2 1 2 -3
2 4 2 1 25
-1 1 -1 -2 -5