Inputs have to be validated before allowing any kind of processing or operations to be performed on it.
This is extremely important because , an unhandled wrong input might have the complete ability to crash a system.
You can read a character string from the user with scanf, then convert it to an integer with strtol.
If you find any bug or error, please feel free to raise an issue. The condition will be as follows: is shown to the user and finally we are returning false; that is very important.Importantance of returning false It's very important to use the return false statement after the condition block that return false so if validation determines that the business requirements are not met then the form cannot be submitted.C has some good validation techniques that can be used to validate most kind of inputs.This post discusses some of the techniques and its shortcomings and what could be done to improve the quality of validation.