C :

#include<stdio.h>
int main()
{
    int a,c,d;
    char b[105];
    scanf("%d",&a);
    getchar();
    while(a--)
    {
        gets(b);
        for(c=0;c<strlen(b);c++)
        {
            if(b[c]==' ')
                    b[c]=',';
        }
        for(c=0;c<strlen(b);c++)
        {
            printf("%c",b[c]);
        }
        printf("\n");
    }
    return 0;
}

C++ :

#include <iostream>
#include <string.h>
using namespace std;
int main()
{
	int N, i, l, j;
	cin >> N;
	cin.get();
	char in[1000];
	string * out = new string [N];
	for(i = 0; i < N ; i++)
	{
		cin.getline(in, 1000);
		l = strlen(in);
		for(j = 0; j < l; j++)
		{
			if(in[j] == ' ')
				in[j] = ',';
		}
		out[i] = in;
	}
	for(i = 0; i < N; i++)
		cout << out[i] << endl;
	return 0;
}

Java :

import java.util.Scanner;

public class Main{
   private static Scanner s = new Scanner(System.in) ;
   
   public static void main(String[] args) {
	   int N = s.nextInt() ;
	   
	   for (int i = 0; i < N; i++) {
		 String num = s.next() ;
		 String name = s.next() ;
		 int s1 = s.nextInt() ;
		 int s2 = s.nextInt() ;
		 int s3 = s.nextInt() ;
		 
		 System.out.println(num+","+name+","+s1+","+s2+","+s3) ;
	   }
   }
}