Lab 4: Functions & Loops

Objectives

The objectives of this lab are to give you practice at using functions and while loops. In addition, you will be expected to begin thinking in terms of the algorithms for your programs before coding. For this lab, we ask you to turn in a text file called algorithms containing the algorithms for the last two problems in addition to the source code. We will also begin looking for proper source code formatting and documentation (comments) in your files.

Programs

You should begin by creating a new directory called Lab4 in your EE160/Labs directory (which you have created in previous labs). All of the program files you write for this lab should be in this Lab4 directory.

• (2 Points). Simple loops.
  • Compile and run countup.c. It is supposed to print the integers 1 through 20 on separate lines and then stop. What does it actually print? Fix it so that it does the right thing. Add comments to the code to document the program properly.
  • Compile and run countdown.c. It is supposed to print the integers 10 down through 1 on separate lines and then print "blastoff". What does it actually print? Fix it so that it does the right thing. Add comments to the code to document the program properly.
• (2 Points). Simple function.
  • Copy your temperature.c file from your Lab3 directory into your Lab4 directory. Modify the program to compute the conversion from Fahrenheit to Celsius in a function called tocelsius(). The prototype for this function is:
    • float tocelsius(float fahrenheit);
    • /* Given: a temperature reading in degrees Fahrenheit
    • Returns: the temperature in degrees Celsius
    • */

Modify the driver, main(), to prompt the user to enter a temperature in Fahrenheit, convert the value using the function and print the result. The driver should loop asking the user for input until a special data value is entered. Since 0 is a valid Fahrenheit temperature, we need something else. Physics tells us that no temperature can be lower than absolute zero (-273 degrees C, or -459 degrees F), let's use -500 as the special data value to terminate Fahrenheit input. Your file will be called temperature.c.

• (2 Points). More functions.
  • (This is a variation of problem 5 in section 3.9 of the text). Copy your temperature.c file to a file called temptbl.c. Add another function to the file:

         int temptable(float start, float stop);

         /*  Given: starting and ending temperatures in degrees Fahrenheit

             The function prints a table of conversions from degrees

             Fahrenheit to degrees Celsius from start to at most stop

             in five degree F increments, one conversion per line.

             Returns: the number of table lines printed.

           */

• The function, temptable(), should use your function, tocelsius(). Modify the driver, main(), to prompt the user to enter the start and stop temperatures and print the table, until the user enters the same value for start and stop.

HOWEVER; before you write ANY code for this program, you should begin by writing the algorithms for the function temptable() and the driver main() IN WORDS. You should write these algorithms in a text file called algorithms, which you WILL turn in for this lab (worth 2 points). You can then use the steps in your algorithm as comments in your source code file.

• (2 Points).
  • Write a program that prints the accumulated value of an initial investment invested at a specified annual interest and compounded annually for a specified number of years. Annual compounding means that the entire annual interest is added at the end of a year to the invested amount. The new accumulated amount then earns interest, and so forth. If the accumulated amount at the start of a year is acc_amount, then at the end of one year the accumulated amount is:
    • acc_amount = acc_amount + acc_amount * annual_interest

Use a function that returns the accumulated value given the amount, interest, and years. The prototype is:

• float calc_acc_amt(float acc_amount, float annual_interest, int years);
• The driver for this program should prompt the user to enter the initial amount, annual interest rate (in decimal, e.g. 0.05 for 5%), and number of years of compounding. The program should process user input until the user enters 0 for the initial amount. AGAIN, before coding this program, you should write the algorithms for calc_acc_amt() and main(), adding them to your algorithms file. Put the source code for this program in the file account.c.

What You Turn In

Use the "grade" command to turn in the algorithms file and the five programs (countup.c, countdown.c, temperature.c, temptbl.c, and account.c). Your command will look like the following.

If you are in Section 001 use:

grade -lab4s1,ee160 algorithms countup.c countdown.c temperature.c temptbl.c account.c

If you are in Section 002 use:

grade -lab4s2,ee160 algorithms countup.c countdown.c temperature.c temptbl.c account.c

If you are in Section 003 use:

grade -lab4s3,ee160 algorithms countup.c countdown.c temperature.c temptbl.c account.c

If you are in Section 004 use:

grade -lab4s4,ee160 algorithms countup.c countdown.c temperature.c temptbl.c account.c

You should verify that you turned in things successfully, which you can do with the command (which simply leaves the file names off from the previous command).

grade -lab4s1,ee160

OR

grade -lab4s2,ee160

OR

grade -lab4s3,ee160

NOTE: after the files are prepared for grading, you will no longer be able to see your file listing using the above command.