Wednesdays Lab

1)It is known that (due to Wilson) a positive integer n > 1 is prime if and only if
(n-1)!+1 is divisible by n. Write a C program that uses this criterion to compute if
an integer n is prime. 
Be sure to separately check the case when n is 1~(note that 1 is not a prime). If n
is less than or equal to zero, print an appropriate message. 

2)Write a program to compute all proper factors of the input number.

The output should be an ordered sequence of divisors of the input along with an
indicator if they are prime or not, with largest divisor first. 

A divisor and its indicator should be enclosed in braces.

For example, on input 42, the output is (21 0) (14 0) (7 1) (6 0) (3 1) (2 1). 
On input 16, the output is (8 0) (4 0) (2 1), etc.
(You must use the method in question 1 to check for primes, other methods will not
be awarded marks)

3)
Write a program using the function getchar() that inputs a rational numbers and
operators and then does that operation on them and prints it using putchar(). You
are not allowed to use scanf or printf.
You can use ascii code information to convert characters to integers.

Example:
If input is
4/2 + 1/2
output is
2.5

If input is
4/2 - 1/2
output is
1.5

If input is
4/2 * 1/2
output is
1.00

If input is
4/2 - 1
output is
1.00 
so on