Trying to figure out why when writing to file, the last character written is being duplicated when cout looks fine on display - fstream

Question

Question = Trying to figure out why the write to file for
myfile.open ("Crypt103Data.txt", ios::out | ios::app);
myfile <<tab2[code1];
myfile.close();
is writing the last character twice to Crypt103Data.txt when the cout which also runs for the same iterations within the while loop displays proper without the extra character write appended to file?
If you enter something like Hello_World you might see something like r$cc7fq7UcX depending on what seed value to entered which gives the output a unique output that is dependent on the seed key. While r$cc7fq7UcX is observed correctly on the screen below the Hello_World , what is written to file is r$cc7fq7UcXX where the last character is written twice and it should only be r$cc7fq7UcX . Not sure why this happens when the cout print to display and file write appended happens for the same iterations within the while loop. Instead of placing a band aid in to trim the last character from the file after each line is written, there must be a fix for this odd bug that someone here might be able to point out. Maybe I am using sloppy programming that is causing for this to occur. I am using the Bloodshed Dev c++ 4.9.9.2 IDE btw
When decrypted, due to this extra character write of the last character the output duplicated, it is decrypted as Hello_Worldd which is the problem.
#include <cstdlib>
#include <iostream>
#include <algorithm>
#include <string>
#include <fstream>
// 12/30/2015 - Added string random shuffle
// 12/31/2015 - Added custom seed for random shuffle so seed acts a crypt key
// 1/4/2016 - Added ability to enter string and have while loop process v1.00
// 1/5/2016 - Added characters , and ; to supported characters which were missing from v1.01
// 1/8/2015 - Source code trash cleanup & offset band aid removed for IF statement logic +1 array offset v1.02
// 1/8/2015 - Added write to file for coded data storage eliminating need to copy/paste output to a text file v1.03
using namespace std;
int main(int argc, char *argv[])
{
int seed1=0;
int code1=0;
int run=1;
int again=1;
int test=1;
char ch1;
char ch2;
while(again==1){
cout<<" Crypt Version 1.03\n\n";
cout<<"XXXXXXXXXXXXXXXXXXXXX\n";
cout<<" Enter Integer Seed: \n"; // Asks user to input integer seed
cout<<"XXXXXXXXXXXXXXXXXXXXX\n\n";
cin >> seed1; // Input user seed
cout<<"\n\n"<<"Crypt String Key =\n\n";
ofstream myfile;
myfile.open ("Crypt103Key.txt", ios::out | ios::app);
myfile <<seed1<<"\n";
myfile.close();
//Initialize Valid Characters for String Shuffle Output
//Note Bug corrected with blank space for \ by use of escape character proceeding
string str="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890!##$%^&*()_-+=?<>:\\/~.,;";
srand(seed1); // Allows user custom seeded starting algorithm position for random
random_shuffle(str.begin(), str.end()); // Shuffle the string
cout << str << "\n\n\n"; // Output the shuffle sequence
//Pass String Output into an array to pair up pointer value with associated character
string tmp = str; //Pass str output to string tmp
char tab2[128]; // Memory Allocation for array population
strncpy(tab2, tmp.c_str(), sizeof(tab2)); //string copy tmp into tab2 array
tab2[sizeof(tab2) - 1] = 0;
cout<<"Enter Info to Crypt in correct case\n";
cout<<"To Exit Inner Program enter ( ` ) \n\n\n";
while(run==1){
cin>>ch1;
if (ch1=='A'){
code1=0;
}
else if (ch1=='B'){
code1=1;
}
else if (ch1=='C'){
code1=2;
}
else if (ch1=='D'){
code1=3;
}
else if (ch1=='E'){
code1=4;
}
else if (ch1=='F'){
code1=5;
}
else if (ch1=='G'){
code1=6;
}
else if (ch1=='H'){
code1=7;
}
else if (ch1=='I'){
code1=8;
}
else if (ch1=='J'){
code1=9;
}
else if (ch1=='K'){
code1=10;
}
else if (ch1=='L'){
code1=11;
}
else if (ch1=='M'){
code1=12;
}
else if (ch1=='N'){
code1=13;
}
else if (ch1=='O'){
code1=14;
}
else if (ch1=='P'){
code1=15;
}
else if (ch1=='Q'){
code1=16;
}
else if (ch1=='R'){
code1=17;
}
else if (ch1=='S'){
code1=18;
}
else if (ch1=='T'){
code1=19;
}
else if (ch1=='U'){
code1=20;
}
else if (ch1=='V'){
code1=21;
}
else if (ch1=='W'){
code1=22;
}
else if (ch1=='X'){
code1=23;
}
else if (ch1=='Y'){
code1=24;
}
else if (ch1=='Z'){
code1=25;
}
else if (ch1=='a'){
code1=26;
}
else if (ch1=='b'){
code1=27;
}
else if (ch1=='c'){
code1=28;
}
else if (ch1=='d'){
code1=29;
}
else if (ch1=='e'){
code1=30;
}
else if (ch1=='f'){
code1=31;
}
else if (ch1=='g'){
code1=32;
}
else if (ch1=='h'){
code1=33;
}
else if (ch1=='i'){
code1=34;
}
else if (ch1=='j'){
code1=35;
}
else if (ch1=='k'){
code1=36;
}
else if (ch1=='l'){
code1=37;
}
else if (ch1=='m'){
code1=38;
}
else if (ch1=='n'){
code1=39;
}
else if (ch1=='o'){
code1=40;
}
else if (ch1=='p'){
code1=41;
}
else if (ch1=='q'){
code1=42;
}
else if (ch1=='r'){
code1=43;
}
else if (ch1=='s'){
code1=44;
}
else if (ch1=='t'){
code1=45;
}
else if (ch1=='u'){
code1=46;
}
else if (ch1=='v'){
code1=47;
}
else if (ch1=='w'){
code1=48;
}
else if (ch1=='x'){
code1=49;
}
else if (ch1=='y'){
code1=50;
}
else if (ch1=='z'){
code1=51;
}
else if (ch1=='1'){
code1=52;
}
else if (ch1=='2'){
code1=53;
}
else if (ch1=='3'){
code1=54;
}
else if (ch1=='4'){
code1=55;
}
else if (ch1=='5'){
code1=56;
}
else if (ch1=='6'){
code1=57;
}
else if (ch1=='7'){
code1=58;
}
else if (ch1=='8'){
code1=59;
}
else if (ch1=='9'){
code1=60;
}
else if (ch1=='0'){
code1=61;
}
else if (ch1=='!'){
code1=62;
}
else if (ch1=='#'){
code1=63;
}
else if (ch1=='#'){
code1=64;
}
else if (ch1=='$'){
code1=65;
}
else if (ch1=='%'){
code1=66;
}
else if (ch1=='^'){
code1=67;
}
else if (ch1=='&'){
code1=68;
}
else if (ch1=='*'){
code1=69;
}
else if (ch1=='('){
code1=70;
}
else if (ch1==')'){
code1=71;
}
else if (ch1=='_'){
code1=72;
}
else if (ch1=='-'){
code1=73;
}
else if (ch1=='+'){
code1=74;
}
else if (ch1=='='){
code1=75;
}
else if (ch1=='?'){
code1=76;
}
else if (ch1=='<'){
code1=77;
}
else if (ch1=='>'){
code1=78;
}
else if (ch1==':'){
code1=79;
}
else if (ch1=='\\'){ // Escape Character \ needed to allow \ check
code1=80;
}
else if (ch1=='/'){
code1=81;
}
else if (ch1=='~'){
code1=82;
}
else if (ch1=='.'){
code1=83;
}
else if (ch1==','){
code1=84;
}
else if (ch1==';'){
code1=85;
}
else if (ch1=='\`'){ //Escape Character \ before ` to exit
run=0; //Run = False at 0 and leaves while loop
}
else {
cout<<"Invalid Input = No Match\n\n";
}
cout<<tab2[code1];
myfile.open ("Crypt103Data.txt", ios::out | ios::app);
myfile <<tab2[code1];
myfile.close();
}// end inner while loop
//Add line return in file to seperate the data per line
myfile.open ("Crypt103Data.txt", ios::out | ios::app);
myfile <<" "<<"\n";
myfile.close();
test=1;
while(test==1){
system("CLS");
cout<<"Enter Y to continue or N to end \n\n\n";
cin>>ch2;
if (ch2=='N'||ch2=='n'){
again=0;
test=0;
}
else if (ch2=='Y'||ch2=='y'){
again=1;
test=0;
run=1;
system("CLS");
}
else {
cout<<"Invalid Input, please choose Y or N \n\n";
test=1;
}
}
} // end outter while loop
system("CLS");
system("PAUSE");
return EXIT_SUCCESS;
}