Construct a Pseudocode to take three numbers and print largest and smallest among them.

Sure, here is a pseudocode to solve the problem:

1. Start
2. Declare variables num1, num2, num3, largest, smallest
3. Read values for num1, num2, num3
4. Assume num1 is the largest and smallest
   Set largest = num1
   Set smallest = num1
5. If num2 is greater than largest then,
   Set largest = num2
6. If num3 is greater than largest then,
   Set largest = num3
7. If num2 is less than smallest then,
   Set smallest = num2
8. If num3 is less than smallest then,
   Set smallest = num3
9. Print largest
10. Print smallest
11. End

This pseudocode will take three numbers as input and then it will compare each number with the others to find the largest and smallest numbers. It first assumes the first number is the largest and smallest, then it checks the other two numbers one by one. If it finds a number larger than the current largest, it updates the largest. Similarly, if it finds a number smaller than the current smallest, it updates the smallest. Finally, it prints out the largest and smallest numbers.