UMBC CMSC201, Computer Science I, Fall 1994 Sections 0101, 0102 and Honors

Tuesday October 18, 1994

Assigned Reading: 5.6

Handouts (available on-line): none

Topics Covered:

• A program that rounds numbers within a given precision. Sample run. The meaning of functions like floor can be found in the Unix manual pages for floor by typing man floor.
• A second program that rounds numbers within a given precision using the standard pow function instead of our home-brewed version (see sample run).
• When we use a function we should be careful to call the function with parameters that are of the same type as declared in the function's prototype. Here's a program that violates this dictum; it lets the C compiler do the type conversion. It works (see sample run), but I consider this very poor programming style. If the C compiler cannot convert the type of the actual parameter to the type of the formal parameter, as in this program, the compiler should give a compile time error.
• The calendar program. We discussed many aspects of Top-Down design (also known as "stepwise refinement") with regards to the calendar program. Then we developed the program in steps.
  • Step 1 is a small loop that prints the calendar for one month, given the number of days in the month and the weekday of the first day of the month. See program and sample run.
  • Step 2 is another small program that uses a function to determine the weekday of a day x days after a certain weekday. (E.g., what is the weekday of the day that is 365 days after a Monday?) See program and sample run.
  • Step 3 puts Step 1 and Step 2 together as a "trial test". We print the calendars for several months in a row, assuming all months have 31 days. It's not what we want in the final program, but we can check if our strategy works. See program and sample run.
  • Step 4 was not shown in class. We steal some functions from the textbook's calendar program to compute the number of days in a given month and the number of days in a given year. See program and sample run.
  • Step 5 puts it all together and now we have our own version of the calendar program that is somewhat different from the textbook's version. Both work, but we got to experience how we might put a larger program together. See program and sample run.