以下是一個使用Fortran面向對象編程的示例代碼，用于讀寫Surfer grd文件：

module GridFile
??implicit?none
??type?::?Grid
????character(len=100)?::?filename
????integer?::?ncols
????integer?::?nrows
????real?::?xllcorner
????real?::?yllcorner
????real?::?cellsize
????real,?allocatable?::?data(:,:)
??end?type?Grid
??contains
??subroutine?read_grid_file(grid,?filename)
????type(Grid),?intent(out)?::?grid
????character(len=*),?intent(in)?::?filename
????integer?::?fileunit,?i,?j
????grid%filename?=?filename
????!?打開文件
????open(newunit=fileunit,?file=filename,?status='old',?action='read')
????!?讀取文件頭
????read(fileunit,?*)?grid%ncols
????read(fileunit,?*)?grid%nrows
????read(fileunit,?*)?grid%xllcorner
????read(fileunit,?*)?grid#yllcorner
????read(fileunit,?*)?grid%cellsize
????!?分配數據數組
????allocate(grid%data(grid%ncols,?grid%nrows))
????!?讀取數據
????do?j?=?1,?grid%nrows
??????do?i?=?1,?grid%ncols
????????read(fileunit,?*)?grid%data(i,?j)
??????end?do
????end?do
????!?關閉文件
????close(fileunit)
??end?subroutine?read_grid_file
??subroutine?write_grid_file(grid)
????type(Grid),?intent(in)?::?grid
????integer?::?fileunit,?i,?j
????!?打開文件
????open(newunit=fileunit,?file=grid%filename,?status='replace',?action='write')
????!?寫入文件頭
????write(fileunit,?*)?grid%ncols
????write(fileunit,?*)?grid%nrows
????write(fileunit,?*)?grid%xllcorner
????write(fileunit,?*)?grid#yllcorner
????write(fileunit,?*)?grid%cellsize
????!?寫入數據
????do?j?=?1,?grid%nrows
??????do?i?=?1,?grid%ncols
????????write(fileunit,?*)?grid%data(i,?j)
??????end?do
????end?do
????!?關閉文件
????close(fileunit)
??end?subroutine?write_grid_file
end?module?GridFile
program?Main
??use?GridFile
??type(Grid)?::?mygrid
??!?讀取Grid文件
??call?read_grid_file(mygrid,?'input.grd')
??!?對Grid數據進行處理
??!?寫入Grid文件
??call?write_grid_file(mygrid)
??
end?program?Main

在上述示例代碼中，Grid類型定義了一個Surfer grd文件的基本屬性和數據。read_grid_file子程序用于從文件中讀取Surfer grd文件的數據并存儲到Grid類型對象中，而write_grid_file子程序用于將Grid類型對象的數據寫入Surfer grd文件。主程序Main則演示了如何使用這些子程序來讀取和寫入Surfer grd文件。
請注意，上述示例代碼僅演示了如何讀取和寫入Surfer grd文件的基本步驟，并未包含完整的錯誤處理和異常情況處理。在實際應用中，可能需要添加適當的錯誤檢查和處理代碼，以確保程序的穩定性和可靠性。