Chapter 2 Elementary Programming编程入门：2章基本编程编程入门.ppt

Notes for Casting 1. Casting does not change the variable being cast. double d = 4.5; int i = static_castint(d); // d is not changed 2. The GNU C++ compiler will give a warning when you narrow a type Using static_cast to avoid such a warning * Example: Keeping Two Digits After Decimal Points Listing 2.10: to displays the sales tax with two digits after the decimal point. * SalesTax Show the following output and count how many type conversions are done. Check Point * double f = 12.5F; f = static_castint(f); int i = f; cout“f is “ f endl; cout“i is “ i endl; §2.7 Software Development Process * Requirement Specification System Analysis System Design Implementation Testing Deployment Maintenance To understand the problem: what the software must do. To analyze the data flow: What is input/output. The process to obtain output from input. Coding, to translate the design into programs. Stage 1. Requirement specification Allow the user to enter the annual interest rate, loan amount, and number of years of payments Compute and display the monthly payment and total payment amount Example: Compute Loan Payments * Stage 2. System analysis The output is monthly payment and total payment It can be obtained from The necessary input : monthly interest rate, number of loan years, and loan amount Example: Compute Loan Payments * Stage 3. System design Identify the steps in the program (algorithm) Let user enter the input Annul rate in integer Convert annual rate to monthly rate Compute monthly payment using the formula Compute the total payment amount Display results Example: Compute Loan Payments * Stage 4. Implementation Listing 2.11 Stage 5. Testing Design test data covering all cases Example: Compute Loan Payments * ComputeLoan The problem: To change a given amount of money into smaller monetary units. Floating amount in dollars ? list of monetary units Major steps Convert dollars into cents Divide cents to find dollars Divide remaining c