# Non-homogeneous Dirichlet BC at a point **URL:** \ **Category:** General Discussion\ **Created:** [April 20, 2023, 5:10pm UTC](https://community.freefem.org/t/non-homogeneous-dirichlet-bc-at-a-point/2410 "2023-04-20T17:10:52Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![sumantkr](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/sumantkr/32/2681_2.png) [@sumantkr](https://community.freefem.org/u/sumantkr)\ **Post date:** [April 20, 2023, 5:10pm UTC](https://community.freefem.org/t/non-homogeneous-dirichlet-bc-at-a-point/2410/1 "2023-04-20T17:10:52Z")
Dear All, can we impose a non-homogeneous Dirichlet boundary condition at a point in a square domain? Ex: u\_xx + u\_yy = f(x, y) over a square AB, BC, CD, and DA are four boundaries of a square. So, how to impose, u(A) = non-zero value in FreeFEM Thanks!!! ---
**Author:** ![cmd](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/cmd/32/67_2.png) [@cmd](https://community.freefem.org/u/cmd)\ **Post date:** [April 25, 2023, 7:21am UTC](https://community.freefem.org/t/non-homogeneous-dirichlet-bc-at-a-point/2410/2 "2023-04-25T07:21:06Z")
As far as I know, this cannot be done using the `on()` function. However, when solving a linear system, Ax=b you can always lock a DOF to a value by setting a row of the matrix A to all zeros except for a one at the point corresponding your DOF of interest. Then set the corresponding DOF in b to the desired value of the Dirichlet condition. ---
**Author:** ![sumantkr](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/sumantkr/32/2681_2.png) [@sumantkr](https://community.freefem.org/u/sumantkr)\ **Post date:** [April 25, 2023, 11:17am UTC](https://community.freefem.org/t/non-homogeneous-dirichlet-bc-at-a-point/2410/3 "2023-04-25T11:17:08Z")
Thanks @cmd. This makes sense. I’ll implement it further.