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lecture4.cpp
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lecture4.cpp
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#include <iostream>
#include <fstream>
#include <sstream>
using namespace std;
int main(int argc, char* argv[])
{
//expecting four things on the command line
if (argc < 4)
{
cout << "not enough parameters for this program" << endl;
}
else
{
//check for parameters
for (int i = 0; i < argc; i++)
{
cout << "parameters " << i << ": " << argv[i] << endl;
}
//the first parameter is the name of the executable
//second is the number of lines in the file
//third is the input file
//fourth is the output file
}
}
///////////////////////////////////////////////////////////////////
//pointer is a special kind of variable that contains a memory address
void psasbyval(int a);
void passbyref(int &a);
int main()
{
int jenny = 5;
int *jennypointer; //pointint to data type int
jennypointer = &jenny;
int billy = 2;
int jimmy = 3;
cout << "What's Jenny? " << jenny << endl;
cout << "What's reference to Jenny (&): " << &jenny << endl;
cout << "What's jennypointer? " << jennypointer << endl;
cout << "What's stored at jennypointer? " << jennypointer << endl;
//so what's the difference between references and pointers
//pointers can be reassigned, references cannot
cout << "Billy: " << billy << endl;
count << "Jimmy: " << jimmy << endl;
//Q: Can you move jenny reference to jimmy reference?
//&jenny = &billy
//A: NO
//Q: Can you set jenny pointer to billy's reference?
//jennypointer = &billy
//A: YES
//now, what's in jennypointer when we dereference it?
//cout << "jennypointer is now << jennypointer << endl;
cout << "dereferencing jennypointer: " << *jennypointer << endl;
passbyval(jenny);
cout << "What's Jenny after pass by val? " << jenny << endl;
passbyref(jenny);
cout << "What's Jenny after pass by ref? " << jenny << endl;
passbyval(jimmy); //shouldn't change jimmy
passbyref(billy); //should change billy
cout << "jimmy is " << jimmy << endl;
cout << "billy is " << billy << endl;
cout << "Jennypointer is now " << jennypointer << endl;
cout << "dereferencing jennypointer: " <<< *jennypointer << endl;
}
void passbyval(int a)
{
++a;
}
void passbyref(int &a)
{
//this will increase a by one
++a;
}