I have the belows error in my program please help! I update it!!

<pre lang="C++">#include <iostream>
#include <fstream>
#include <conio.h>
#include <string>
#include <stdio.h>
#include <stdlib.h>

using namespace std;


int main()
{

    int accumulator =0;
    int n;
    int i=0;
    int x=00;

    string c;
    const char *b;
    int memory[100];
    ifstream ifs;
    int counter=0;
    ifs.open("program.txt",ios::in);
    if(ifs){
        for(int i=0 ; i<100 && !ifs.eof();i++){
            getline(ifs,c);
            b=c.c-str();
            memory[i]=atoi(b);
            counter++;
        }
        ifs.close();
    }else{
        cout<<"Error";
    }

    for(int i=0 ;i<counter;i++){
        cout<<x<<" ?"<<memory[i]<<endl;
    }




    cout<<"*** Welcome to Simpletron! ***\n";
    cout<<"*** Please enter your program one instruction ***\n";
    cout<<"*** (or data word) at a time. I will type the ***\n";
    cout<<"*** location number and a question mark (?).  ***\n";
    cout<<"*** You then type the word for that location. ***\n";
    cout<<"*** Type the sentinel -99999 to stop entering ***\n";
    cout<<"*** your program. ***\n";



    //2 raghame avale ram
    int opCode ;
    //2raghame dovome ram
    int operand ;


    int instructionRegister;
    for(int i=0;i<counter;i++){
        instructionRegister=memory[i];
        opCode =instructionRegister/100;
        operand =instructionRegister%100;
        switch (opCode ){
        case 10:
            //Read a word from the keyboard into a specific location in memory.
            cout<<"plz enter a number:\n";
            cin>>memory[operand];
            break;
        case 11:
            //Write a word from a specific location in memory to the screen.
            cout<<memory[operand]<<'\n';
            break;
        case 20:
            //Load a word from a specific location in memory into the accumulator.
            accumulator=memory[operand];
            break;
        case 21:
            //Store a word from the accumulator into a specific location in memory.
            memory[operand]=accumulator;
            break;
        case 30:
            //Add a word from a specific location in memory to the word in the accumulator(Resgister) -leave result in accumulator.
            accumulator+=memory[operand];
            break;
        case 31:
            //Subtract a word from a specific location in memory from the word in the accumulator(Resgister) -leave result in accumulator.
            accumulator-=memory[operand];
            break;
        case 32:
            //Divide a word from a specific location in memory into the word in the accumulator(Resgister) -leave result in accumulator.
            accumulator=memory[operand]/accumulator;
            break;
        case 33:
            //Multiply a word from a specific location in memory by the word in the accumulator(Resgister) -leave result in accumulator.
            accumulator=memory[operand]*accumulator;
            break;
        //case 40:
           // i = memory[operand] - 1;
            //break;
       // case 41:
            //Branch to a specific location in memory if the accumulator is negative.
          //  i = (accumulator < 0 ? (memory[operand] - 1) : i);
            //break;
       // case 42:
            //Branch to a specific location in memory if the accumulator is zero.
            //i = (accumulator == 0 ? (memory[operand] - 1) : i);
           // break;
        //case 43:
           //Halt the program has completed its task.
          // i = 101;
          // break;
        /*default:
        Cout<<"Error: Wrong operation code. Program halt";
          break;*/
        }
    }


    getch();
    return 0;
}

Error   1   error C2039: 'c' : is not a member of 'std::basic_string<_Elem,_Traits,_Ax>'    c:\users\sama\documents\visual studio 2010\projects\11\11\11.cpp    32
Error   2   error C3861: 'str': identifier not found    c:\users\sama\documents\visual studio 2010\projects\11\11\11.cpp    32
    3   IntelliSense: class "std::basic_string<char, std::char_traits<char>, std::allocator<char>>" has no member "c"   c:\users\sama\documents\visual studio 2010\projects\11\11\11.cpp    32
    4   IntelliSense: identifier "str" is undefined c:\users\sama\documents\visual studio 2010\projects\11\11\11.cpp    32