South 고등학교 3학년 Informatics

Chapters: 5

1. Information culture

Information science in society · Careers in information science · Information protection · Information security · Software copyright · Cyber ethics

Digital Society: How Information Technology Changes Our Lives – A digital society (also called an information society) is a society where making, sharing and using information with computers and networks is a main part of life, work and government. Information moves fast, reaches everywhere and can be copied at almost no cost. Software has changed shopping, banking, health, school and friendship. New jobs appear (app developer, data analyst) while some old jobs shrink. Every online action leaves data, so privacy matters. Not everyone is connected (the digital divide), and too much screen time or gaming can harm health. A good digital citizen uses the benefits and manages the risks.
Career Planning: From Knowing Yourself to Your First Job – Career planning has five steps. 1) Know yourself: interests, skills and values. 2) Explore career families and find out the work, study needed, pay and demand. 3) Plan a pathway with SMART goals and a plan B. 4) Search for jobs with a CV, cover letter, digital portfolio and interview practice. 5) Make the move from school to work and keep learning, because careers change over a lifetime.
Cybersecurity: Threats and How We Stop Them – Cybersecurity protects computers, networks and data. It aims for confidentiality, integrity and availability (the CIA triad). Common threats are malware, phishing and social engineering, brute-force password attacks and denial of service. Defences include strong authentication, encryption, firewalls, anti-malware software, updates, access control and backups.
Data Protection and Intellectual Property Rights – Intellectual property (IP) is a creation of the mind, such as a story, song, program, invention or logo. Intellectual Property Rights (IPR) give the creator control over its use. Copyright protects creative works (text, music, art, software code) automatically once created; a patent protects a new, useful invention for about 20 years and must be applied for; a trademark protects brand names, logos and slogans. Plagiarism is presenting someone else's work as your own without credit. Infringement is using protected IP without permission (copyright, patent or trademark infringement). Public licences let creators share on their own terms: Creative Commons (BY, SA, NC, ND) for creative works, and software licences such as GPL (copyleft: modified versions must stay open) and Apache (permissive: can be used in closed products with notices).
Digital Footprints and Netiquette – A digital footprint is the trail of data we leave online. Active footprints are shared on purpose (posts, comments, forms); passive footprints are collected without us noticing (cookies, browsing history, location, IP address). Footprints are hard to erase and can be seen by others later. We live in a digital society where learning, banking, shopping and government services are online; a responsible user of it is a digital citizen (netizen). Net etiquette means being ethical (respect copyright, share reliable information), respectful (privacy, diversity, no bullying) and responsible (avoid oversharing, don't feed trolls). Communication etiquette asks us to be precise, polite and credible; social media etiquette asks us to choose passwords and privacy settings wisely, think before uploading, and verify before sharing.

2. Data and information

Representing information · Data in computing · Collecting and analysing · Managing information

Number Systems and Encoding – A number system is a way to write numbers using a set of digits and a base. Decimal (base 10) uses 0–9, binary (base 2) uses 0 and 1, octal (base 8) uses 0–7, and hexadecimal (base 16) uses 0–9 and A–F. To go from decimal to any base, divide repeatedly by the base and read remainders bottom to top; for fractions, multiply by the base and read the integer parts top to bottom. To go to decimal, multiply each digit by its place value and add. Binary ↔ octal uses groups of 3 bits, binary ↔ hex groups of 4. Text is stored with encoding schemes: ASCII (7-bit, 128 characters), ISCII (8-bit, Indian scripts) and Unicode (every script), stored as UTF-8 (1–4 bytes) or UTF-32 (4 bytes).
Data Handling: Collect, Organise and Show Data – Data is a set of facts, such as answers, counts or measurements. Data can be qualitative (words) or quantitative (numbers); numbers are discrete (counted) or continuous (measured). We collect data by surveys, observation, experiments or from existing sources, then organise it with tally marks into a frequency table. We show it with the right graph: bar graphs to compare groups, pie charts to show parts of a whole, line graphs for change over time and scatter graphs for links between two variables. Computers store data as structured tables or unstructured text, images and sound.
Data Analysis – Data analysis means turning raw data into answers. It follows a cycle: ask a question, collect data, clean it (remove errors, repeats and blanks), organise and transform it, analyse it with summaries such as mean, median, range and patterns, show it with a good chart, and draw a careful conclusion. Watch for outliers, small samples and bias, and remember that a correlation between two things does not prove that one causes the other. Data must also be stored safely and used with permission.
Database Concepts: DBMS, Relations and Keys – Keeping data in separate files causes duplication, inconsistency and poor security. A database stores related data in one organised place, and a DBMS (like MySQL) is the software that manages it. In the relational model, data is kept in tables (relations) made of columns (attributes) and rows (tuples); a domain is the set of allowed values of a column. A candidate key uniquely identifies each row; one is chosen as the primary key and the others are alternate keys.

3. Abstraction and algorithms

Analysing complex problems · Modelling problems · Decomposing hard problems · Control structures in algorithms · Algorithm performance

Introduction to Problem Solving – Problem solving on a computer has stages: analyse the problem (inputs, outputs, rules), develop an algorithm (a finite, clear, ordered set of steps), code it in a programming language, test it with different inputs, and debug (find and remove errors). An algorithm can be shown as a flowchart (oval = start/stop, parallelogram = input/output, rectangle = process, diamond = decision, arrows = flow) or as pseudocode (structured plain English). Decomposition breaks a big problem into smaller sub-problems that are solved separately and then joined.
Algorithm Complexity: How Fast Does an Algorithm Grow? – Many algorithms can solve the same problem, but some need far more steps. We measure an algorithm by counting its basic steps as the input size n grows, not by stopwatch seconds. Big O notation names the growth: O(1) constant, O(log n) logarithmic, O(n) linear, O(n log n), and O(n²) quadratic. Linear search is O(n), binary search is O(log n); bubble sort is O(n²), merge sort is O(n log n). Memory used is space complexity.

4. Programming

Text-based languages · Variables and data types · Operators · Standard and file I/O · Control structures · Nested control · Arrays · Functions · Programs for other subjects · Collaborative projects

Programming Basics: Sequence, Selection, Loops and Functions – A program is a set of exact instructions a computer follows. Every program is built from three structures: sequence (steps in order), selection (if/else choices) and iteration (loops). Variables store values. Functions group code into reusable, named blocks, which makes programs modular and easier to test, debug and maintain.
Python Basics: Modes, Variables, Data Types and Operators – Python runs in interactive mode (one line at a time) or script mode (a saved .py file). Blocks are shown by indentation. Variables are names tied to values; every value has a data type, and some types are mutable. Operators build expressions that Python works out by precedence. input() reads text, int()/float()/str() convert types, and debugging fixes syntax, runtime and logical errors.
File Handling in Python: Save Data That Lasts – Variables vanish when a program ends; files keep data on the disk. A text file stores characters in lines, a binary file stores raw bytes (such as pickled Python objects), and a CSV file stores table rows with commas. You open a file with open(path, mode), using an absolute or relative path and a mode such as r, w, a, r+, rb or wb. The with statement closes the file for you. Text files use write, writelines, read, readline and readlines. seek moves the file pointer and tell reports where it is. pickle.dump and pickle.load save and load objects in binary files, letting you search, append and update records. The csv module's writer (writerow, writerows) and reader handle CSV files.
Flow of Control in Python – Flow of control is the order in which statements run. Python has three kinds: sequential (top to bottom), selection (if, if-else, if-elif-else) and repetition (for and while loops). Blocks are marked by indentation (usually 4 spaces after a colon). range(start, stop, step) gives numbers from start up to but not including stop. while repeats as long as a condition is true. break exits a loop at once; continue skips to the next turn. A loop inside another is a nested loop and is used for patterns; loops with an accumulator are used for series sums.
Control Statements in Python: if-else, while and for – Normally Python runs lines one after another (sequence). Control statements change this flow. if-else chooses one of two paths; if-elif-else picks the first true condition from many. while repeats a block while a condition is true; for repeats once for each item of a sequence such as range(start, stop, step).
Lists in Python: Create, Traverse, Change and List Methods – A list is an ordered, changeable collection written in square brackets, like [10, 20, 30]. Items are reached by index (from 0, or negative from the end) and slices. We traverse a list with a for loop, change items in place because lists are mutable, and use functions (len, max, min, sum, sorted, list) and methods (append, insert, extend, remove, pop, sort, reverse, count, index, clear) to work with it.
Functions in Python: Build Your Own Machines – A function is a named block of code that does one job. Python has built-in functions (print, len), functions inside modules (math.sqrt, random.randint) and user-defined functions you write with def. Values sent in a call are arguments; the names that receive them are parameters. Arguments can be positional, keyword or use default values. return sends a value back. Python runs code top to bottom, jumps into a function when it is called and comes back after it. Names made inside a function are local; names made outside are global.

5. Computing systems

Operating systems · Networks · Choosing hardware · Physical computing

Operating System – An operating system (OS) is the main system software that sits between the user and the hardware and manages all resources. Its functions: process management (sharing the CPU between programs), memory management (giving and taking back RAM), file management, device management (through drivers) and security (passwords, permissions). Users talk to the OS through a user interface: command line (CLI), graphical (GUI), touch, voice or gesture. Examples: Windows, Linux, macOS, Android, iOS.
How Networks Grew and How Data Travels – A computer network is a group of connected devices that share data. Networking began with ARPANET (1969), grew into NSFNET (1980s) for universities, and joined with other networks to become the Internet, a network of networks. Every data communication has five parts: sender, receiver, message, communication media and protocol. Bandwidth is the range of frequencies a channel can carry (in Hz); data rate is how many bits travel per second (bps). Every device on a network has an IP address. Data can move by circuit switching (a fixed path is booked first) or packet switching (data is cut into packets that travel on their own).
Basic Computer Organisation – A computer system has hardware (parts you can touch) and software (instructions). Input devices bring data in, the CPU (ALU + Control Unit + registers) processes it, and output devices give results. Memory forms a ladder: registers and cache are tiny and fastest, primary memory (RAM, ROM) holds running programs, and secondary storage (HDD, SSD, pen drive) keeps data permanently. Memory is measured in bits and bytes: 8 bits = 1 byte, and each bigger unit (KB, MB, GB, TB, PB) is 1024 times the one before.
Physical Computing: Making Code Sense and Move – Physical computing joins code to the real world. Sensors measure something (light, temperature, distance, button presses) and turn it into a number. A microcontroller runs a program that decides what to do with that number. Actuators (LEDs, buzzers, motors, screens) act on the world. This input–process–output cycle runs again and again in a loop. Using thresholds, conditions and feedback, we build night lights, smart plant waterers, wearables and interactive art.