Introduction to Computer Science

This unit is your start in computer science. You will write real programs in Python 3, beginning with a single print statement and finishing with programs that read input, make decisions, repeat steps and check their own data.

You will learn to use variables and constants with the four basic data types (integers, floats, strings and Booleans), and you will see what is really inside the computer: how numbers are stored in binary and hexadecimal, and how text is stored with ASCII and Unicode. You will write arithmetic, string, comparison and Boolean expressions in the correct order of operations, plan programs with the input, process, output model, and use the three control structures: sequence, selection (if, elif, else) and repetition (while and for loops), including nested structures that count, total and find the highest and lowest values. All the way through, and especially in the last two lessons, you will practise professional code maintenance: reading error messages, fixing syntax, run-time and logic errors, tracing code, testing it with a full range of test cases, and writing clean, well-named, well-commented code.

No programming experience is needed. If you took Grade 9 math (MTH1W), you have already read and changed some short Python programs; this unit starts again from the beginning and goes much deeper. All you need is a computer, Chromebook or tablet with Python 3 (free from python.org, the Thonny editor, or a free online Python 3 editor). Every lesson has worked examples, programs whose output is shown, a hands-on activity, lots of practice with answers, and a short quiz. Type the code yourself rather than copying it: it is the best way to learn, and copied indentation from a web page can contain invisible characters that Python rejects.

The next unit, Arrays and Subprograms, builds on this one with lists (one-dimensional arrays), string tools, functions, and searching and sorting.

Curriculum: The Ontario Curriculum, Grades 10 to 12: Computer Studies (2008), Introduction to Computer Science, Grade 11, University Preparation (ICS3U), strand A. Programming Concepts and Skills: A1.1 to A1.4 (data types and expressions), A2.1 to A2.3 (control structures and simple algorithms) and A4.1 to A4.5 (code maintenance). Expectations A1.5, A1.6 and A3 (arrays and subprograms) are taught in the unit Arrays and Subprograms, which also continues A4.

In Programming Basics you learned to store one value in a variable and to control a program with selection and loops. In this unit you learn to handle many values at once and to organize code into reusable parts.

The first half is about one-dimensional arrays, which in Python are lists: their structure (elements, indexes and bounds), how to declare, initialize, access and modify them, and the classic algorithms that work on them: counting, totals and averages, highest and lowest values, linear search, sorting (selection sort and bubble sort), and inserting into or deleting from a list. You will also treat strings as sequences and take substrings.

The second half is about subprograms. You will use existing ones (built-in functions, the math and random modules, string methods), then write your own functions and procedures with parameters and return values, learn exactly how parameter passing works for numbers and lists, and use local and global scope correctly. You will design programs modularly with structure charts and a main() function.

Throughout, you practise professional code maintenance: reading error messages, tracing, fixing syntax, run-time and logic errors, documenting code with docstrings, and validating programs with a full range of test cases. The unit ends with a complete menu-driven project.

All code is Python 3. You only need a computer with Python installed (IDLE or Thonny are free) or a free browser-based Python.

Writing code is only one part of making software. In this unit you will learn how programmers plan, design, build, test and deliver programs that people can rely on.

You will start with problem-solving strategies (stepwise refinement, divide and conquer, working backwards, examples and extreme cases, tables and trial and error), the input-process-output model, and how to work independently and in teams. Then you will design programs with industry-standard tools: flow charts, pseudocode, structure charts, data flow diagrams and UML, using modular, reusable code, program skeletons and user-friendly interfaces. You will design algorithms to specifications: formulas (hypotenuse, primes, area and circumference), inserting into and deleting from sorted arrays, and exception handling (division by zero, roots of negatives, bad input). Finally you will follow the software development life cycle: clarifying specifications, planning with Gantt, critical path and PERT charts, testing with test plans, debugging by tracing and printing variable state, and writing status reports, ending with a mini project that uses everything.

Remember from the other units of this course: Programming Basics taught variables, input and output, selection and loops; Arrays and Subprograms taught lists and functions. This unit assumes both. Every code sample uses Python 3 and runs exactly as shown; all you need is a computer with Python (IDLE or Thonny) or a free browser-based Python. Every lesson has worked examples, a hands-on activity, lots of practice and a short quiz. These skills lead directly to ICS4U (Grade 12 Computer Science).

Curriculum: The Ontario Curriculum, Grades 10 to 12: Computer Studies (2008, revised), Introduction to Computer Science, Grade 11, University Preparation (ICS3U), strand B. Software Development: B1.1 to B1.3 (problem-solving strategies), B2.1 to B2.5 (designing software solutions), B3.1 to B3.3 (designing algorithms to specifications) and B4.1 to B4.6 (the software development life cycle).

In this unit you will learn how the computer you program actually works, how to keep your work organized and safe, and what the tools you code with really do. You will start inside the computer: the CPU, RAM, ROM, cache, storage, motherboard, power supply, video and sound hardware, and how to read their specifications (GHz, GB, TB, MT/s, Mbps) with real arithmetic. You will compare peripherals such as monitors, printers and scanners, use a weighted decision matrix to recommend a computer for a real user, and follow a program as the CPU fetches, decodes and executes it, using a pretend CPU written in Python.

Next you will organize files on local, shared and cloud drives, learn how viruses, worms, Trojan horses, spyware, adware, ransomware and malicious macros work, write a system protection plan, and back up and archive your files using the 3-2-1 rule. Finally you will explore the IDE and its debugger, learn to work independently with documentation, and explain the differences between source code and machine code, interpreters and compilers, and operating systems, applications and programming languages.

You need a computer with Python 3 (or a free browser-based Python) and an IDE such as IDLE or Thonny. Every code sample has been run and shows its exact output. This unit works alongside the other ICS3U units, Programming Basics, Arrays and Subprograms, Software Development and Topics in Computer Science, and connects to the Grade 12 course ICS4U (Computer Science).

Curriculum: The Ontario Curriculum, Grades 10 to 12: Computer Studies (2008, revised), Introduction to Computer Science, Grade 11, University Preparation (ICS3U), strand C. Computer Environments and Systems: C1 (relate the specifications of computer components to user requirements: C1.1 to C1.4), C2 (use appropriate file maintenance practices to organize and safeguard data: C2.1 to C2.3) and C3 (demonstrate an understanding of the software development process: C3.1 to C3.5).

This unit looks beyond the code. You will start with environmental stewardship: what computers cost the planet (e-waste, energy, paper) and our health (posture, eyes, activity), the policies that reduce that harm, the ways computers help save resources through modelling and resource management, and the recyclers, refurbishers and programs that give old equipment a second life in Ontario and Canada.

Next you will tour emerging areas of computer science research: cryptography and security, artificial intelligence and data mining, robotics and computer vision, parallel and distributed computing, geographic information systems and human–computer interaction, and research that joins computer science with other fields such as biology, linguistics and climatology. Each tour includes a short Python program you can run and change. Then you will research one area yourself and report on it as a website, presentation or video.

Finally you will look ahead: career trends at the local, national and global levels, experiential learning such as co-op and job shadowing, supports for students choosing non-traditional paths, postsecondary programs (entrance requirements, length and costs), and the Essential Skills and Work Habits of the Ontario Skills Passport.

This unit uses the Python you learned in Programming Basics and Arrays and Subprograms, and connects to Software Development (design, Gantt charts, user-friendly interfaces) and Computer Environments and Systems (hardware, backups). Every lesson has explanations, worked examples, tested Python code, a hands-on activity, practice with answers and a quiz. You need a computer with Python 3 or a free browser-based Python editor, and internet access for the research activities.

Curriculum: The Ontario Curriculum, Grades 10 to 12: Computer Studies (2008), Introduction to Computer Science, Grade 11, University Preparation (ICS3U), strand D. Topics in Computer Science: D1.1 to D1.4 (environmental stewardship and sustainability), D2.1 to D2.3 (emerging areas of computer science research) and D3.1 to D3.5 (postsecondary education and career prospects).