CPE101 - Lab 3

Lab 3 -- Selection Structures
CPE101
Winter 2008

Updates

None yet.

Objectives

To become familiar with the various control structures in C

Overview

Control structures modify the flow of execution in a program. You can use control structures to run a particular part of your program while skipping some other portions.

In this lab, you will be looking at the if-else and switch control statements. In order for your control structures to properly decide which code to execute, the structures must have properly coded condition tests. These conditions are simple expressions which will evaluate to either true or false. You use these conditions to decide whether or not to run some particular code. For example, to run some code if an integer a equals and integer b, use the statement:

    if (a == b) {
        ...run these commands if the condition is true...
   }

   You can include an 'else' also:

    if (a == b) {
       ...run these commands if the condition is true...
   } else {
       ...otherwise run these commands...
   }

Logical Operators

Logical operators are used to combine multiple condition tests in an 'if' statement. For example, if you would like to run some code only if a equals b and c equals d, then you would use the following:

    if (a == b && c == d) {
        ...run these commands if the condition is true...
   }

AND (&&)

operand 1	operand 2	result
false	false	false
false	true	false
true	false	false
true	true	true

OR (| |)

operand 1	operand 2	result
false	false	false
false	true	true
true	false	true
true	true	true

Lab Requirements

For this lab, you will write a program that determines the day of the year (1 to 366) for a given date.

You can determine if a year is a leap year with the following rules:

A year is a leap year if it is divisible by 4 except:

If a year is divisible by 100, then it is a leap year only if it is divisible by 400

Part 1

Write a program which accepts 3 integers. The integers will represent the month, day, and year for a date. The program should prompt for each number individually. Here are some sample runs:

	Enter the month: 3
	Enter the day: 1
	Enter the year: 2000

	Day number: 61


	Enter the month: 3
	Enter the day: 1
	Enter the year: 2001

	Day number: 60


	Enter the month: 3
	Enter the day: 1
	Enter the year: 1900

	Day number: 60

Your program should have a function leap that returns a 1 if the argument is a leap year. It should return 0 otherwise.

If the user enters an invalid day, month, and/or year, the program should output a day number even if the answer is incorrect.

Part 2

Modify Part 1 so that your program does error checking. Your program should check that the month is between 1 and 12. It should also check that the day is between 1 and 31. It does not have to check that the day is valid for a given month.

	Enter the month: 13
	Enter the day: 1
	Enter the year: 2008

	Invalid date

Handin

    1. If necessary, move your source (part1.c and part2.c) to vogon.
    2. Log on to vogon via some terminal somewhere.
    3. Change directory (cd), as necessary, to the directory where your source file(s) are.
    4. Compile and test your source on vogon using the required compiler flags (-Wall -ansi -pedantic)
    5. Use the handin command being sure to replace xx with your lecture section number.

11:59 vogon ~$ handin mhaungs Lab3-xx part1.c part2.c

Demonstration

You will be required to demonstrate you program in lab on the due date.