Use top-down modular approach and pseudocode to create suitable program to solve this problem. Validating your input data is also essential.
Create program using pseudocode along with the structure to do following.
Permit user to enter series of temperatures in degrees Celsius (C) terminated by -999. For each one, determine the corresponding temperature in degrees Fahrenheit (F). Conversion formula is F = (9 * C) / 5 + 32.