Problem with encryption

I am new to pascal.I need to make a program that read a whole text and a line of letters which will replace the alphabet.My problem is that i don't know how to read the text and keep every single letter.

while not eoln do

this is what i use.aba is where i place the letters. it does'nt start and it says:command terminated by signal 24


  • Here's a simple single file encryption/decryption program using a simple xor encryption method. The beauty of this is that the same code does the job both ways.[code][color=Blue]{ Compiler TP/BP7 }

    {$M 16384,0,655360}

    var f_in,f_out:file; { Files as untyped }
    f_in_name,f_out_name,pwd:string;{ File names }
    pwd_value,bytes_read:word; { Password checksum, read counter }
    i:word; { Counter }
    buffer:array[0..16383] of byte; { 16 kByte buffer for data }

    pwd_value:=0; { Init password checksum with 0 }
    write('Enter filename to encrypt/decrypt: ');readln(f_in_name);
    write('Enter filename to decrypt/encrypt: ');readln(f_out_name);
    write('Enter password: ');readln(pwd);
    for i:=1 to length(pwd) do begin { Calculate BSD checksum of the password }
    pwd_value:=(pwd_value shr 1) + ((pwd_value and 1) shl 15); { Parity bit }
    inc(pwd_value,ord(pwd[i])); { Increment password checksum }
    pwd_value:=pwd_value and $ffff; { Keep it whitin bounds }
    randseed:=pwd_value; { Init random seed with password checksum }
    assign(f_in,f_in_name);reset(f_in,1); { Open input file for read }
    if ioresult<>0 then begin { Check if input file exists }
    writeln(f_in_name,' not found, exiting.');
    assign(f_out,f_out_name);rewrite(f_out,1);{ Create output file }
    while not(eof(f_in)) do begin
    blockread(f_in,buffer,16384,bytes_read); { Read a chunk for input file }
    for i:=1 to bytes_read do { Encrypt or Decrypt (Same thing) }
    buffer[i]:=buffer[i] xor byte(random(256));{ Simple XOR encryption }
    blockwrite(f_out,buffer,bytes_read); { Output encrypted/decrypted data }
    close(f_in);close(f_out); { Close both files }
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