Blank answers dynamic array - c++

Question

Been given a task to change my code to dynamic array.
The program asks you to input array size 1 to 100. After that input vowels 1 by 1 with the normal array teikums[100]; it outputted the vowels and the vowel amount.
Been given a task to make dynamic array without the "new".
But after adding the dynamic array:
char *teikums = (char*)malloc(100);
It outputs blank space.
#pragma hdrstop
#pragma argsused
#include <string>
#include <tchar.h>
#include <conio.h>
#include <stdio.h>
#include <math.h>
#include <iostream>
#include <iomanip>
#include <sstream>
using namespace std;
int main() {
char *teikums = (char*)malloc(100);
int c, i, count, patsk; // Patskani
char yesno; // Atkartosanas Mainigais
do {
cout << " " << teikums[i];
system("cls"); // Notira Ekranu
do {
patsk = 0; // Pieskir vertibu
cout << "Input array size 1-100: ";
cin >> count;
if (count > 100 || count < 1) {
cout << "Array cant be lower or higher than 0\n";
}
} while (count > 100 || count < 1);
do {
cout << "Input " << count << "letters one by one\n";
for (i = 1; i <= count; i++) {
cin >> teikums[i];
if (!((teikums[i] >= 'a' && teikums[i] <= 'z') || (teikums[i] >=
'A' && teikums[i] <= 'Z'))) {
cout << "Error! Only input letters\n";
i = i - 1;
}
}
} while (i <= count);
cout << "\nUsed Vowels:";
for (i = 0; teikums[i] != '\0'; i = i + 2) {
if (teikums[i] == 'a' || teikums[i] == 'e' || teikums[i] == 'i' ||
teikums[i] == 'o' || teikums[i] == 'u' || teikums[i] == 'A' ||
teikums[i] == 'E' || teikums[i] == 'I' || teikums[i] == 'O' ||
teikums[i] == 'U') {
++patsk;
cout << " " << teikums[i];
teikums[i] = 0;
}
}
cout << "\nVowel ammount: " << patsk;
cout << ("\nDo you wish to continue(Y/Else):");
// prasa lietotajam vai velas atkartot
cin >> yesno;
if (yesno == 'y' || yesno == 'Y') {
}
else {
return 0;
}
} while (tolower(yesno) != 'n');
getch();
}

Answer 1

In this line:
cout << " " << teikums[i];
i is not initialized and therefore it contains an indeterminate value.
This is causing all your troubles. But there may be other problems elsewhere, I didn't check all details.
If it worked with char teikums[100]; it's pure coincidence.
Google "C undefined behaviour" for more information.