Satck Input/Output files

[lolwe]

Create a program that contains the following functions:
-create two dynamic stacks with integer data contained in an external file.
-Sort items in stacks by the selection sort method
-Record outputs in an external file.
Main function main ()-menu selection functions and check the status of the data

How to write input and output function for the stack?

#include "stdlib.h"
#include "memory.h"
#include "stdio.h"
#include "fstream"
#include "iostream"
#include "iomanip"
#include "string"

typedef struct elem { int key; elem *next; } *pelem;
typedef struct stack { pelem start; } *pstack;

void push(pstack s, int n) {
	pelem p = s->start;
	s->start = (pelem)malloc(sizeof elem);
	s->start->key = n;
	s->start->next = p;
}

int pop(pstack s) {
	int n = -1;
	pelem p = s->start;
	if (p != NULL) {
		n = p->key;
		s->start = p->next;
		free(p);
	}
	return n;
}

int is_empty(pstack s) {
	return s->start == NULL;
}

pstack create_stack() {
	pstack t = (pstack)malloc(sizeof stack);
	memset(t, 0, sizeof stack);
	return t;
}

void selection_sort(pstack s) {
	pstack ret = create_stack();
	pstack temp = create_stack();
	while (!is_empty(s)) {
		int current = pop(s);
		while (!is_empty(s)) {
			int n = pop(s);
			if (n < current) {
				int swap = current;
				current = n;
				n = swap;
			}
			push(temp, n);
		}
		push(ret, current);
		s->start = temp->start;
		temp->start = NULL;
	}
	s->start = ret->start;
}

void file_input(){???}

void file_output(){???}

void display_file(int type){
	int n;
	std::string name;           
	switch (type){               
	case 1:
		name = "inputf.txt";
		break;
	case 2:
		name = "outputf.txt";
		break;
	}
	std::ifstream file;
	file.open(name.c_str(), std::ios::in);
	if (file){               
		int i(1);          
		std::cout << "Conten of file " << name << " is:" << std::endl;
		std::cout << std::setw(8) << "Element";
		std::cout << std::setw(14) << "Value";
		while (file >> n){          
			std::cout << std::endl << std::setw(5) << i;   
			std::cout << std::setw(14) << n;         
			i++;      
		}
		file.close();      
		if (i == 1)std::cout << std::endl << "Failat e prazen." << std::endl;
	}
	else std::cout << std::endl << "Greshka pri otvarianeto na faila!";
}

int main(){
	/* MENU */
	std::cout << "MENU" << std::endl;
	std::cout << "[1] - Input data infile ( inputf.txt )." << std::endl;
	std::cout << "[2] - Sort " << std::endl;
	std::cout << "[3] - Save file ( outputf.txt )." << std::endl;
	std::cout << "[4] - Print input.txt" << std::endl;
	std::cout << "[5] - Print output.txt" << std::endl;
    std::cout << "[0] - Izhod ot programata." << std::endl;
	char chc;
	while (true){
		std::cout << "Choose operation -> ";
		std::cin >> chc;
		switch (chc)
		{
		case '0':
		{
					exit(0);
					break;
		}
		case '1':
		{
					file_input();
					break;
		}
		case '2':
		{          pstack s1 = create_stack();
					selection_sort(s1);
					while (!is_empty(s1))
						printf("%d ", pop(s1));
		}

		case '3':
		{
					file_output();
					break;
		}

		case '4':
		{
					display_file(1);
					break;
		}

		case '5':
				   display_file(2);
				    break;

		default: std::cout << "Invalid choice!!!" << std::endl;
		}
		std::cout << std::endl;
	}
	return 1;
}