why don't you use something like this

void createtextfile1()
{
 ofstream fout("Text.txt",ios::app);
 char string[80], yes;
 do
 {	
    cout<<"Enter a line of text? \n"; gets(string);//similar to cin , but coniders the spaces
    fout<<string<<endl;
    cout<<"Add More line[Y/N]? "; cin>>yes;
 }
 while (yes=='Y' || yes=='y');
 fout.close();
}

you could use the above code and put in those other if else conditions.

Hope it helps

Dot operator (.) is binary operator.It is also called the membership operator. On the left hand side of the dot operator (.) is the structure variable name and on the right hand side of dot (.) operator is the data member name of the structure variable.
Just like pointer to fundamental data type (char / int / float / double) we can also have pointer to derived type like pointer to structure (class) type. A structure (class) type has to be declared first then pointer to that structure (class) type is to be created. One major difference between pointer to a fundamental data type and pointer structure (class) type is the use of dereferencing (indirection) operator. For a pointer to a fundamental type unary star operator (*) is used as dereferencing (indirection) operator but generally for pointer to structure (class) type binary arrow operator (->) is used as dereferencing (indirection) operator. An arrow operator consists of two characters: dash/minus (-) followed by greater than sign (>).

why don't you just use

double cuberoot(double x)
{
 double a=pow(x,1/3);
 return a;
}

check your line 150

int 1=a, 2=b, 3=c, 4=d, 5=e, 6=f;

this should be modified as

int a=1,b=2,c=3,d=4,e=5,f=6;

You should always assign a value to a variable eg . a=1;
but you cannot assign a variable to a number value. 1=a;
it will be flagged as syntax error

what do you mean by unknown numbers ? Giving an example or a screenshot to us might make it clear as to what actually is happening