This and following weekly labsheets provide both 'basic' and optional 'advanced' tasks.
If you're able to complete all of the basic tasks each week, then you're considered to be keeping up with the unit.

The optional advanced tasks, which we'll term chili questions, are prefixed by one or more chilis: 🌶 The more chilis, the more difficult the task. More advanced programmers should be able to complete a number, if not all, of these tasks.

Preparation

Before commencing this labsheet, please read the following introductory pages:

• OS and C compiler software
• Linux and C compiler basics
• Frequently used commands

Next, kick out the cobwebs

A number of students in previous years have indicated that they had difficulties 'getting started' with the first couple of CITS2002 Labsheets. When questioned, they indicated that they hadn't written even a simple program 'for a while' - for some this was since first semester, for some since first year.

So these introductory tasks are just designed to refresh your programming knowledge, and confidence; to get you to the point where you'll again have these skills at your fingertips (some students are even a bit rusty on how to build and run a program).

The tasks are language agnostic, so attempt them using any operating system, any programming language, and any editor you choose (at this stage, they may appear a bit difficult in C). There'll be no sample solutions, but it should be obvious to you if your solution is correct.

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Refresher tasks

1. [integer arithmetic, basic loop] When Australia first adopted decimal currency in 1966, coins had the denominations of 1c, 2c, 5c, 10c, 20c, and a round 50c. If a person purchased something valued at $1 or less, and paid with a $1 note (yes!), write a program to list the minimum number of coins, and their demoninations, that they should receive as change.

2. [calling external function] Using your chosen programming language, write a short program to print out today's date and time (example output: Thu Jul 27 18:19:34 2023). The actual format is unimportant.

3. 🌶 [floating-point numbers] In Lecture-2 we stated that floating-point values are rarely, if ever, used in operating system kernels - primarily because they cannot be represented exactly on contemporary computers and, so, we must use them with great caution, or not at all. In your chosen programming language, write an small program displaying sufficient decimal-points to 'expose' the problem of inaccuracy.

4. [integer arithmetic, 1D array] Revise (or learn) how to generate a non-negative random integer in your chosen programming language. Saturday Lotto involves drawing 6 unique numbers, between 1 and 45. Write a simple program to choose and display your 6 lucky numbers.

5. 🌶 [2D array, nested loop] Fill a 2D array of, say, 10x20 integers with non-negative random integers. Without using your language's builtin/standard sort() method/function, print out the second largest value in the array.

If you're interested in more, short, programming challenges, there are many websites providing examples and their solutions in many programming languages:

• Programmr's Coding Challenges
• Edabit Challenges
• Reddit's list of Programming Challenge Websites
• The 10 Most Popular Coding Challenge Websites

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Labsheet 1 tasks

Using rotate.c :

Modify the program to perform rot-3, rotation by 3 characters (or the traditional Caesar-cipher). Extend the program to print out each character of the ciphered text one per line instead of all the characters on one line. Extend the program to print out on each line not only the ciphered character, but also the original character too. Extend the program to print out on each line not only the original and ciphered characters, but also the "position" of the character in the text. Extend the program to handle both upper-case and lower-case letters. The program rotate.c requires 4 C-preprocessor #include directives to read the declarations of some standard C functions from C header files. Remove (and eventually replace) each #include line, in turn, to determine which required functions are declared in each file.

7. 🌶 Extend the program so that it can accept multiple arguments, performing the ciphering process on each argument to the program.

8. 🌶 Extend the program so that it reads the rotation amount (the amount to rotate each character by) as the first argument to the program. You will need to use the atoi function to convert the text argument into a number.

9. 🌶 🌶 Extend the program so that all arguments to the program can be either text or numbers. If an argument is text, the text is ciphered using the current rotation amount (initialised to 13). If an argument is a number, the rotation amount changes to this value and all subsequent cipherings (up to the next number argument) use this new rotation amount.

10. 🌶 🌶 Extend the previous version of the program so that textual arguments can represent files. If a text argument can be opened as a file (see man fopen), perform the ciphering on the contents of the file. Otherwise, treat the arguments as before: if an argument is text, the text is ciphered using the current rotation amount (initialised to 13), or if an argument is a number, the rotation amount changes to this value and all subsequent cipherings (up to the next number argument) use this new rotation amount.