DecToBin / BinToDec converter

#include <stdio.h>

int DecToBin(void){
    int n, o, i = 0;
    int *data;

    printf("Enter number: ");
    scanf("%d" , &n);

    printf("Dec to bin: ");
    while(n){
        o = n%2;
        if(o == 1){
             data[i] = 1;
        }
        else{
             data[i] = 0;
        }
        i++;
        n /= 2;
    }
    for(i - 1; i >= 0; i--){
        if(data[i] == 1){
            printf("1");
          }
        else if(data[i] == 0){
            printf("0");
        }
    }
    printf("\n\n");
}

int BinToDec(void){
    int i, sum = 0, d = 1;
    char *data;
    printf("Enter number: ");
    scanf("%s", data);

    for(i = strlen(data)-1; i >= 0; i--){
        if(data[i] == '1'){
            sum += d;
        }
        d = d * 2;
    }

    printf("Bin to dec: %d\n\n", sum);
}

int main(void)
{
    int s = 0;

    while(1){
        printf("Enter 1 to convent 10 in 2\nEnter 2 to convent 2 in 10\nEnter 3 to exit\n>");
        scanf("%d", &s);
        printf("\n");

        if(s == 1){
            DecToBin();
        }
        else if(s == 2){
            BinToDec();
        }
        else if(s == 3){
            break;
        }
    }
}