CS31 Lab 2: C: Sorting

Due: Tuesday, February 4, before 11:59 PM

Weekly-lab warm-up

Textbook Reference: Conditionals and Loops, Functions, and Operating on Arrays

Class piazza page for questions and answers about lab assignment

CS31 github org, Git help

Useful Unix Commands, vi (and vim) quick reference

Practice with C programming basics: declaring variables, types, arrays, and functions.

Writing C code and functions that uses statically declared arrays.

Practice writing and using C functions. Pass by value: basic types and array parameters.

C I/O: scanf, printf, and using a simplified file reading library.

More practice with top-down design.

Using a Makefile.

Use git to clone a repository and share code with your partner.

When run, your program’s output should look like the output shown below from a run of a working program. This example doesn’t show every possible run or error handling, but should give you some idea of what a correct program run looks like. To make my job of grading easier, please make your output match the example as closely as possible (to print just a new line use: printf("\n");)

$ ./sorter floats.txt
Reading file named floats.txt
The file contains 10 floating point numbers, ranging from 0.00 to 9.00
The unsorted values are: 9.00 8.00 4.00 5.00 7.00 3.00 2.00 1.00 6.00 0.00
The sorted values are: 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00

As in the example above, your program should print the following four items in a human-readable way:

You should store the set of floating point values only once (e.g., keep only one array, don’t copy all the values to a second array.) You may assume that there will never be more than 100 values to sort, and you can use any sorting algorithm you like, it doesn’t need to be fancy. You should not attempt to use merge sort, as we haven’t yet discussed all the C functionality that you’ll need to implement it.

Your program should exit gracefully if you detect an error that’s not your code’s fault (for example, if it was given the name of an invalid input file). Be sure to check those return values!

It should be evident that you applied top-down design when constructing your submission. In addition to main(), you should have at least two non-trivial functions, each with a specific role. (See the Implementation Recommendations section below for suggestions.)

Your code should be commented, modular, robust, and use meaningful variable and function names. Each function should include a brief description of its behavior.

Your program should not use global variables. If a function needs a value from its caller, then that value should be passed in as a parameter. If a function needs to store variables, then those should be declared as local variables inside the function. If you don’t know what a global variable is, no problem, you won’t make the mistake of using one!

Your code should compile cleanly with no errors or warnings and should not crash unexpectedly during execution.

Code you submit should have my "TODO" comments removed (these are my notes to you, as you implement them remove the "TODO").

Before even starting to write code, use top-down design to break your program into manageable functionality.

Test your code in small increments. It’s much easier to localize a bug when you’ve only changed a few lines.

Many of the functions that you’ll write to deal with arrays will need to know the size (length) of the array. Unlike Python, C does NOT keep that information around (there is no len() function). If a function needs to know the array length, you should make that a parameter to the function.

When printing floating point values, use formatting directives to make the output more readable by limiting the number of digits that get printed after the decimal point. For example, using %.2f in the format string for printf() limits the printed float to two digits after the decimal.

For values that will never change in your program, you can compile in constants using #defines. There are some example with the starting point code.

Use CNTRL-C to kill a running program stuck in an infinite loop.

To debug programs with command line options in gdb, include the command line arguments when you start the program with the gdb run command:

Post on Piazza, attend ninja sessions, and/or come to office hours if you have questions!