[Pascal] Encrypt Message

{Encrypt the message                                                      }
{Make a board with m*n size                                               }
{Write the message into the board with VertDir, each box contains a letter}
{Write the message in HorizDir, that is the encrypted message             }
{For example:                                                             }
{Normal Message: "This_is a_test"                                         }
{Board size: 2*7                                                          }
{Board:                                                                   }
{       T i _ s a t s                                                     }
{       h s i _ _ e t                                                     }
{Encrypt Message: "Ti_satshsi__et"                                        }
{See? Nobody will understand}
{This is useful when you need to have a secret conversation with someone  }
{Every one is the conversation need to use this program                   }
{This program can use files to send messages, or you can directly send msg}
{This program will have Graphic User Interface soon                       }
{Enjoy this lame program                                                  }
{You need to make 2 files                         }
Program Sec_Msg;
Uses crt;
Var
   A: Array [1..100,1..100] of char;
   i, j, m, n, k: Integer;
   S, Files, Msg, RecFiles: String;
   Ans: char;
   f: Text;
Procedure Send;
          Begin
               clrscr;
               Write('Input size of board: '); Readln(m, n);
               Write('Input message: '); Readln(S);
               Write('Input file: '); Readln(Files);
               k:=1;
               For i:=1 to m do
                   For j:=1 to n do
                      Begin
                           A[i,j]:=S[k];
                           k:=k+1;
                      End;
               Msg:='';
               For j:=1 to n do
                   For i:=1 to m do
                       Msg:=Msg+A[i,j];
               Assign(f,Files);
               Rewrite(f);
               Writeln(f,Msg);
               Close(f);
          End;
Procedure Receive;
          Begin
               clrscr;
               Write('Input files: '); Readln(files);
               Write('Input files to receive: '); Readln(RecFiles);
               Assign(f,Files);
               Reset(f);
               Readln(f,S);
               Read(f,m,n);
               Close(f);
               k:=1;
               For i:=1 to m do
                   For j:=1 to n do
                       Begin
                            A[i,j]:=S[k];
                            k:=k+1;
                       End;
               Msg:='';
               For j:=1 to n do
                   For i:=1 to m do
                       Msg:=Msg+A[i,j];
               Assign(f,RecFiles);
               Rewrite(f);
               Writeln(f,Msg);
               Close(f);
          End;
Procedure Nhap;
          Begin
               Write('Receive or Send? (R/S) ');
               Ans:=ReadKey;
               While (Upcase(Ans)<>'R') and (Upcase(Ans)<>'S') do
                     Begin
                          Writeln('Press again: ');
                          Ans:=Readkey;
                     End;
               If Upcase(Ans)='R' then
                  Receive;
               If Upcase(Ans)='S' then
                  Send;
          End;
Begin
     clrscr;
     Nhap;
End.