Void Func

#include <stdio.h>
#include <fstream> // ofstream ifstream
#include <iostream>
#include <cstring>
//#include <algorithm> //count
using namespace std;


unsigned int filesize(const char* fname){
    ifstream f(fname);
    string dummy;
    unsigned int lines=0;
    /*
    //-------------------
    while( getline(f, dummy) )
    {
        lines++;
    }
    //-------------------
    */

    char c;
    while ( !f.eof() )
    {
        c = f.get();
        if ( c == '\n' )
            lines++;
    }

    //-------------------
    //count requires algorithm
    //lines= count(istreambuf_iterator<char>(f), istreambuf_iterator<char>(), '\n');
    //-------------------
    f.close();
    cout<<lines<< " lines in file "<<fname<<endl;
    return lines;
}

int main(){
    string s;
    unsigned int c=0;
    const unsigned int lines = filesize("fruit.txt");

    char** v;
    v = new char* [lines];
    ifstream inf("fruit.txt");
    while ( getline(inf,s) )
    {
        v[c] =  new char [s.size()+1]; // +1 for null byte .c_str()
        //strncpy(v[c], s.c_str(), s.size()+1);
        strcpy(v[c], s.c_str());
        c++;
    }
    cout << "v =  "<<v<<endl; //memory address
    cout << "v[0] =  "<<v[0]<<endl; // first line
    cout << "v[0][0] =  "<<v[0][0]<<endl; //first char of first line
    cout<<c<<endl;
    for (unsigned int x=0; x<c; x++)
    {
        printf("%s\n", v[x]);
        delete[] v[x];
        v[x]=nullptr;
    }
    delete[] v;
    v=nullptr;
    return 0;
}

#include <iostream>
using namespace std;

struct Movie {
    string title;
    int year;
};

int main (){
    string s;

    Movie a;
    Movie* p;
    //p = &a;
    p = new Movie;

    a.title = "Star Trek";
    (*p).title="Star Wars";
    (*p).year=1977;

    cout << p->title <<endl;
    cout << (*p).year << endl;
    
    p->title="Indiana Jones";
    p->year=1990;

    cout << p->title <<endl;
    cout << p->.year << endl;

    delete p;
    return 0;
}

#include <iostream>

using namespace std;
//void* is a pointer with no type
//void* can not be dereferenced

void foo(void* v){
    //cout << *v <<endl; //cannot dereference a void pointer
    int* p= (int*)v; //cast v into a int*
    //double* p= (double*)v;
    cout << *p <<endl;
}

int main(){
    int i(3);
    double d(4.9);
    foo(&i);
    //foo(&d);
    return 0;
}

#include <stdio.h>
#include <iostream>
using namespace std;

int sum(int a, int b);
int subtract(int a, int b);
int mul(int a, int b);
int divi(int a, int b);


int main(void){
    int(*q)(int, int) = &sum;
    cout << (*q)(3,4) <<endl;
    /*
    int(*p[4]) (int , int );
    p[0] = &sum; // address of sum()
    p[1] = &subtract; // address of subtract()
    p[2] = mul; // address of mul()
    p[3] = divi; // address of div()
    */
    int(*p[4]) (int , int )= { sum, subtract, &mul, &divi };

    int i, j;
    printf("Enter two numbers: ");
    scanf("%d %d", &i, &j); //like cin>>i  cin>>j
    for (int x=0 ; x<4; x++)
    {
      cout<<  (*p[x])(i,j) <<endl; //call functions through pointer
    }

    return 0;
}

int sum(int a, int b){
    return a + b;
}

int subtract(int a, int b){
    return a - b;
}

int mul(int a, int b){
    return a * b;
}

int divi(int a, int b){
    if(b)
        return a / b;
    else
        return 0;
}