参考答案

Option Base 1
Private Sub Form_Click()
    Const N = 5
    Const M = 5
    Dim Mat(M, N) As Integer
    Dim i, j, t
    Open App.Path & "\" & "datain.txt" For Input As #1
    For i = 1 To N
        For j = 1 To M
            Input #1, Mat%(i, j)
        Next j
    Next i
    Close #1
    Print
    Print "初始矩阵为："
    Print
    For i = 1 To N
        For j = 1 To M
            Print Tab(5 * j); Mat(i, j);
        Next j
        Print
    Next i
    Print
    Print
    For i = 1 To N
        For j = 1 To M
            t = Mat(1, j)
            Mat(1, j) = Mat(3, j)
            Mat%(3, j) = t
        Next j
    Next i
    Print
    Print "交换第一行和第三行后的矩阵为："
    Print
    For i = 1 To N
        For j = 1 To M
            Print Tab(5 * j); Mat(i, j);
        Next j
        Print
    Next i
End Sub