如何在c编程中将用户输入与字符串进行比较

We are trying to execute the if statements based on what the user inputs. For example if the user input Yen then we want the if statement to be executed and the conversion to yen be calculated. After the user has input how many gallons of gas the calculations are made and we are left with a total cost. We want to then let the user choose a currency that they would like to convert the total cost into. We have given the user three choices. If the user inputs something that is not any of the given choices then the user is allowed to re-enter a choice again. One the user does enter one of the 3 choices then we want the currency conversion to be executed.We are trying to execute the if statements base