diff --git a/src/becke_numerical_grid/example.irp.f b/src/becke_numerical_grid/exemple.irp.f
similarity index 100%
rename from src/becke_numerical_grid/example.irp.f
rename to src/becke_numerical_grid/exemple.irp.f
diff --git a/src/bitmask/exemple.irp.f b/src/bitmask/exemple.irp.f
new file mode 100644
index 00000000..7800e556
--- /dev/null
+++ b/src/bitmask/exemple.irp.f
@@ -0,0 +1,81 @@
+subroutine example_bitmask
+ use bitmasks ! you need to include the bitmasks_module.f90 features
+ implicit none
+ BEGIN_DOC 
+! subroutine that illustrates the main features available in bitmask
+ END_DOC
+ integer :: i,j
+ print*,''
+ print*,'**************'
+ print*,'**************'
+ print*,'MO class: to set the various type of MO class, see the following exectuable'
+ print*,'qp_set_mo_class'
+ print*,'**************'
+ print*,'number of core orbitals = ',n_core_orb
+ print*,'list of the core orbitals '
+ do i = 1, n_core_orb
+  write(*,'(2(I3,X))')i,list_core(i)
+ enddo
+
+ print*,'number of inact orbitals = ',n_inact_orb
+ print*,'list of the inact orbitals '
+ do i = 1, n_inact_orb
+  write(*,'(2(I3,X))')i,list_inact(i)
+ enddo
+
+ print*,'number of act orbitals = ',n_act_orb
+ print*,'list of the act orbitals '
+ do i = 1, n_act_orb
+  write(*,'(2(I3,X))')i,list_act(i)
+ enddo
+
+ print*,'number of virt orbitals = ',n_virt_orb
+ print*,'list of the virt orbitals '
+ do i = 1, n_virt_orb
+  write(*,'(2(I3,X))')i,list_virt(i)
+ enddo
+ print*,''
+ print*,'**************'
+ print*,'**************'
+ print*,'manipulating bitstrings (usefull for determinant representation)'
+ print*,'**************'
+ integer(bit_kind), allocatable :: key(:)
+ print*,'Size of the integers used to represent all the orbitals '
+ print*,'bit_kind = ',bit_kind
+ print*,'Number of bits in the integers ',bit_kind_size
+ print*,'Number of integers to represent all the orbitals on integer'
+ print*,'N_int = ',N_int
+ allocate(key(N_int))
+ print*,'**** '
+ print*,' initialize a bistring to zero '
+ do i = 1, N_int
+  key(i) = 0_bit_kind
+ enddo
+ print*,'print a human readable representation of the bitstring'
+ call bitstring_to_str( output, key, N_int )
+ print *,  trim(output)
+ integer :: i_orb
+ character*(2048) :: output
+ 
+ do i_orb = 1, min(4,mo_tot_num) ! you set the first four bits to 1 in key
+  call set_bit_to_integer(i_orb,key,N_int)
+ enddo
+ print*,'print a human readable representation of the bitstring'
+ call bitstring_to_str( output, key, N_int )
+ print *,  trim(output)
+ print*,''
+ integer :: n_elements
+ integer, allocatable :: list_occ(:)
+ allocate(list_occ(N_int*bit_kind_size))
+ call bitstring_to_list( key, list_occ, n_elements, N_int)
+ print*,'number of bits set to 1 = ',n_elements
+ print*,'list of bits set to 1 '
+ do i = 1, n_elements
+  write(*,'(2(I3,X))')i,list_occ(i)
+ enddo
+ call clear_bit_to_integer(2,key,N_int) ! you set to 0 the second bit
+ print*,'print a human readable representation of the bitstring'
+ call bitstring_to_str( output, key, N_int )
+ print *,  trim(output)
+
+end
diff --git a/src/determinants/exemple.irp.f b/src/determinants/exemple.irp.f
new file mode 100644
index 00000000..24b52232
--- /dev/null
+++ b/src/determinants/exemple.irp.f
@@ -0,0 +1,165 @@
+subroutine example_determinants
+ use bitmasks ! you need to include the bitmasks_module.f90 features
+ implicit none
+ BEGIN_DOC 
+! subroutine that illustrates the main features available in determinants 
+ END_DOC
+ print*,'a determinant is stored as a binary representation of the occupancy of the spatial orbitals'
+ print*,'see the bitmask module for more information about that '
+ print*,'a spin determinant is an array of (N_int) integers of type bit_kind (see bitmask for more information)'
+ print*,'A determinant containing alpha and beta electrons is an array of dimension (2,N_int)'
+ integer(bit_kind), allocatable :: det_i(:,:)
+ allocate(det_i(N_int,2))
+ print*,'det_i(1,:) alpha spins '
+ print*,'det_i(2,:) beta  spins '
+ integer :: i,j
+ print*,'initialize det_i to an electron occupation corresponding RHF or ROHF: ref_bitmask '
+ do i = 1, N_int
+  det_i(i,1) = ref_bitmask(i,1) 
+  det_i(i,2) = ref_bitmask(i,2) 
+ enddo
+ print*,''
+ print*,'print a human readable representation of the determinant '
+ call print_det(det_i,N_int)
+ print*,'doing a single excitation on top of det_i'
+ integer :: h1,p1,s1,i_ok
+ h1 = 1
+ p1 = elec_alpha_num + 1
+ s1 = 1
+ print*,'h1 --> p1 of spin s1'
+ print*,'i_ok == +1 : excitation is possible '
+ print*,'i_ok == -1 : excitation is NOT possible '
+ call do_mono_excitation(det_i,h1,p1,s1,i_ok)
+ print*,'h1,p1,s1,i_ok'
+ print*, h1,p1,s1,i_ok 
+ if(i_ok == -1)then
+  print*,'excitation was not possible ' 
+  stop
+ endif
+ call debug_det(det_i,N_int)
+ print*,'computing the interaction between ref_determinant and det_i '
+ double precision :: h0i,hii,h00
+ call i_H_j(det_i,det_i,N_int,h0i)
+ print*,'  < ref | H | det_i > = ',h0i
+ print*,'computing the diagonal Hamiltonian matrix element of det_i '
+ call i_H_j(ref_bitmask,det_i,N_int,hii)
+ print*,'< det_i | H | det_i > = ',hii
+ print*,'computing the first-order coefficient of det_i with H0=EN '
+ double precision :: c_i 
+ call i_H_j(ref_bitmask,ref_bitmask,N_int,h00)
+ c_i = h0i/(h00 - hii)
+ print*,'c_i^{(1)} = ',c_i
+ print*,''
+ print*,'doing another single excitation on top of det_i'
+ h1 = elec_alpha_num 
+ p1 = elec_alpha_num + 1
+ s1 = 2
+ call do_mono_excitation(det_i,h1,p1,s1,i_ok)
+ print*,'h1,p1,s1,i_ok'
+ print*, h1,p1,s1,i_ok 
+ call i_H_j(det_i,det_i,N_int,h0i)
+ print*,'  < ref | H | det_i > = ',h0i
+ print*,'computing the diagonal Hamiltonian matrix element of det_i '
+ call i_H_j(ref_bitmask,ref_bitmask,N_int,h00)
+ c_i = h0i/(h00 - hii)
+ print*,'c_i^{(1)} = ',c_i
+ print*,''
+ print*,'Finding the excitation degree between two arbitrary determinants '
+ integer          :: exc(0:2,2,2)
+ double precision :: phase
+ integer :: h2,p2,s2,degree
+ call get_excitation_degree(ref_bitmask,det_i,degree,N_int)
+ print*,'degree = ',degree
+ print*,'Finding the differences in terms of holes and particles, together with the fermionic phase '
+ call get_excitation(ref_bitmask,det_i,exc,degree,phase,N_int)
+ print*,'Fermionic phase for the excitation from ref_bitmask to det_i'
+ print*,phase
+ print*,'put the excitation information in a human readable format'
+ call decode_exc(exc,degree,h1,p1,h2,p2,s1,s2)
+ print*,'s1',s1
+ print*,'h1,p1 = ',h1,p1
+ print*,'s2',s2
+ print*,'h2,p2 = ',h2,p2
+ print*,''
+ print*,'Finding the occupancy of det_i'
+ integer, allocatable :: occ(:,:)
+ integer :: n_occ_ab(2)
+ allocate(occ(N_int*bit_kind_size,2))
+ call bitstring_to_list_ab(det_i, occ, n_occ_ab, N_int)
+ print*,'alpha electrons orbital occupancy'
+ do i = 1, n_occ_ab(1) ! browsing the alpha electrons 
+  print*,occ(i,1)
+ enddo 
+ print*,'beta  electrons orbital occupancy'
+ do i = 1, n_occ_ab(2) ! browsing the beta  electrons 
+  print*,occ(i,2)
+ enddo 
+end
+
+
+subroutine example_determinants_psi_det
+ use bitmasks ! you need to include the bitmasks_module.f90 features
+ implicit none
+ BEGIN_DOC 
+! subroutine that illustrates the main features available in determinants using the psi_det/psi_coef
+ END_DOC
+ read_wf = .True.
+ touch read_wf
+ ! you force the wave function to be set to the one in the EZFIO folder
+ call routine_example_psi_det
+end
+
+subroutine routine_example_psi_det
+ use bitmasks ! you need to include the bitmasks_module.f90 features
+ implicit none
+ BEGIN_DOC 
+! subroutine that illustrates the main features available in determinants using many determinants 
+ END_DOC
+ integer :: i,j
+ integer, allocatable  :: degree_list(:)
+ integer, allocatable :: idx(:)
+ allocate(degree_list(N_det),idx(0:N_det))
+ 
+ print*,'Number of determinants in the wave function'
+ print*,'N_det = ',N_det
+ print*,''
+ print*,'Printing in a human readable format all Slater determinants '
+ do i = 1, N_det
+  call debug_det(psi_det(1,1,i),N_int)  
+ enddo
+ print*,''
+ print*,'Number of states computed '
+ print*,'N_states = ',N_states
+ print*,'Printing the coefficients for all states for all Slater determinants '
+ do j = 1, N_states
+  print*,'State = ',j
+  do i = 1, N_det
+   write(*,'(I9,X,F16.10)')i,psi_coef(i,j)
+  enddo
+ enddo
+ print*,''
+ print*,'Finding the connection through a bielectronic operator in the wave function'
+ print*,'You want to know the connections of the first determinant '
+ !                                 wave function  determinant    exc degree              list
+ call get_excitation_degree_vector(   psi_det  ,  psi_det(1,1,1),degree_list,N_int,N_det,idx)
+ double precision :: hij
+ double precision, allocatable :: i_H_psi(:)
+ allocate(i_H_psi(N_states))
+ i_H_psi = 0.d0
+ print*,'Computing <psi_det(1) | H | psi_det > = \sum_I c_I <psi_det(1)| H | psi_det(I)>'
+ do i = 1, idx(0) ! number of Slater determinants connected to the first one
+  print*,'Determinant connected'
+  call debug_det(psi_det(1,1,idx(i)),N_int)
+  print*,'excitation degree = ',degree_list(i)
+  call i_H_j(psi_det(1,1,1) , psi_det(1,1,idx(i)),hij,N_int)
+  do j = 1, N_states
+   i_H_psi(j) += hij * psi_coef(idx(i),j)
+  enddo
+ enddo
+ print*,'i_H_psi = ',i_H_psi
+end
+
+
+
+
+