Question: I have to read from standard input two numbers as strings, in C. How can I print their sum as a string too? I have:

```
char a[10],b[10];
printf("enter the two numbers");
scanf("%s%s",&a,&b);
char sum[20];
sum=?

```

A little tip,please?
Thank you!

Answer: 
`chars` are 8-bit binary numbers, just like smaller `ints`. We must interpret them to give them meaning as letters.

Your computer probably uses the ASCII standard. In ASCII, the `char` value representing the character `0` does not actually have the numerical value 0. It's 48. Fortunately, the numbers are all consecutive, so `1` is 49, etc.

```
char zero = '0';
printf("%d\n", zero);
char one = '1';
printf("%d\n", one);

> 48
> 49

```

(Note that the `%d` format flag in `printf` means "interpret as an integer".)

Since `chars` are numbers, we can do math with them.

```
char one = '1';
int one_num = one - '0';
printf("%d\n", one_num);

> 1

```

Now, you can implement the addition with decimal digits and carrying just like you'd do on paper.
Convert the strings into numbers using `atoi`, then add them together, and then print the sum using a print function like printf. See [this](http://www.cplusplus.com/reference/cstdlib/atoi/)