Computer Science 381
Programming Unix in C

Winter Immersion 2016, The College of Saint Rose

Lab 2: C Basics
Due: Wednesday, December 23, 2015

In this lab you will gain more experience with the Unix tools and techniques from last week, but the focus is on some of the basics of C programming.

Before you start, create a directory on a Unix or Mac system to contain your work for this lab, and open a file lab2.txt where you will place your answers for this lab's questions.

C Basics

You may work on any C-capable Unix-like system (such as a lab Mac, mogul, or your own Unix-like system).

If you have not already done so, finish reading Chapter 1 of K&R.

Question 1: Consider any C program that uses the printf function. What happens if you leave out the #include <stdio.h> line? Explain briefly. (2 points)

Question 2: Suppose one of the programs from the running example about conversion from Fahrenheit to Celsius is to be modified to print conversions for every degree Fahrenheit from -100 to 1000 and you wish to print 3 digits after the decimal point for each Celsius temperature. What printf function call could be used to print this so that the printed temperatures are aligned nicely? (2 points)

Practice Program: Write a program charcount.c, similar to that in Exercise 1-14 on p. 24 of K&R. Your program should deal only with numeric and alphabetic characters, and should treat upper or lower case characters as equivalent. You also need not print a histogram, you can just print a table of the results. Like the example program on p. 22, your program should read characters from the standard input and print the results to standard output. (10 points)

To run your program, we'll use Unix redirection like we did for the previous lab's output captures. Those used only output redirection with > at the end of the command line. We can also perform input redirection with < after our program name. This lets you run a program that expects input from the keyboard but instead that input will come from the file. For this case, copy the file on mogul in /home/cs381/labs/c-basics/whosonfirst.txt to your directory for this lab. Then run your practice program, redirecting its input from whosonfirst.txt and its output to a file whocounts.txt with a command such as

./charcount < whosonfirst.txt > whocounts.txt

Output Capture: whocounts.txt for 2 point(s)

Practice Program: Write the program in Exercise 1-19 on p. 31 of K&R. Call your program revlines.c. (10 points)

Note: the getline function is now defined in stdio.h. (check text for what it was previously)

Also run this program on the whosonfirst.txt file, this time saving the output in whorev.txt.

Output Capture: whorev.txt for 2 point(s)

Question 3: Briefly describe the major differences between arrays in C, as presented in Chapter 1 of K&R, and arrays in Java. (2 points)

Programming Assignment

Write the program in Exercise 1-20 on p. 34 of K&R. Call your program detab.c. Use a defined constant for the value n, the number of columns between tab stops. Include This program is worth 20 points, broken down as shown at the end of this document.

Reference solutions to all programs are available on mogul in /home/cs381/labs/c-basics.


Please submit all required files as email attachments to terescoj AT by Wednesday, December 23, 2015. Be sure to check that you have used the correct file names and that your submission matches all of the submission guidelines listed on the course home page. In order to email your files, you will need to transfer them from mogul to the computer from which you wish to send the email. There are a number of options, including the sftp command from the Mac command line.


This lab is graded out of 50 points.

Grading Breakdown

Lab questions and output captures 10 points
Practice program charcount.c correctness 10 points
Practice program revlines.c correctness 10 points
detab.c correctness 10 points
detab.c design 3 point
detab.c documentation 3 points
detab.c style 3 point
detab.c efficiency 1 point
Total 50