# Practice #2

### Gilad Ri γ»2 min read

Some nice tricks you all should know:

```
// #1 - the modulo operator (just a reminder):
int x = 125;
int y = 7;
int z = 5;
int divisionRemainder = x % y; // 6
divisionRemainder = x % z; // 0
// #2 - how to get the last digit of a number:
int number = 12345;
int lastDigit = number % 10; // 5
// #3 - how to omit the last digit of a number:
int number2 = 12345;
int shorterNumber = number2 / 10; // 1234
```

And now, let's write down some code!

##
**Exercise #1**

Write a program which gets a number from the user and prints the sum of its digits. For example:

```
Enter a number:
123
The sum of the digits of the number 123 is 6
```

(Hint: use the tricks above).

##
**Exercise #2**

Write a program which gets an integer number from the user and checks if it's a prime number. If it's a prime number the program prints "Prime", and otherwise it prints "Not prime". (Hint: A number is prime if it is not divisible by any **smaller** number). For example:

```
Enter a number:
9
Not prime
Enter a number:
3
Prime
```

##
**Exercise #3**

Write a program which gets from the user an integer and builds a pyramid of asterisks ('*') with a base of this size. For example:

```
Insert the base size of the pyramid:
5
*
***
*****
Insert the base size of the pyramid:
6
**
****
******
Insert the base size of the pyramid
25
*
***
*****
*******
*********
***********
*************
***************
*****************
*******************
*********************
***********************
*************************
```

Pay attention that if the base size is an even number, the head of the pyramid should be "**" and not '*'.

**Good luck!**

####
**Always remember, it's much C-mpler than you thought!**

Regards,

Gilad