Reading a sentence until ENTER key pressed using 2-D char array

I need to read a sentence word by word until "ENTER" key is pressed. I used a do..while loop to read words until ENTER key is pressed. Please suggest me some conditions for checking ENTER key press (or) others ways for reading similar input.

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

int main(){

     char a[100][20]={'\0'};
     int i=0;

     do{
        cin>>a[i++];
     } while( \\ Enter key is not pressed );

     for(int j= 0 ; j < i ; j++)
        cout<< a[j] << " "; 
    return 0;
 }