Difficulty: Beginner | Prerequisites: None
This is the opening lecture of an introductory computer science course. It lays the groundwork for everything that follows: what computer science is, how computers evolved, and why binary matters. If you are joining the course late or skipping ahead, this is the lecture to read first, as later material assumes you know these terms and concepts.
Computer science is the study of how data is processed and stored, covering both theory and practical programming. Computers run on binary (0s and 1s) because their hardware relies on electrical signals that are either on or off. The field spans eight core areas, from programming and algorithms to AI and cybersecurity.
Computer science
The study of computers, algorithms, software, and how data is processed and stored. It spans both theoretical foundations and hands-on programming.
In simple terms, it is the discipline concerned with making computers do useful things, and understanding how they do it.
Hardware
The physical components of a computer: the motherboard, processor, memory chips, drives, keyboard, screen.
Think of it as everything you could pick up and hold.
Software
The programs and applications that run on hardware.
In simple terms, software is the set of instructions that tells the hardware what to do.
Algorithm
A step-by-step set of instructions designed to solve a specific problem.
Think of it as a recipe: follow the steps in order and you get a predictable result.
CPU (Central Processing Unit)
The component that executes instructions and performs calculations. Often called the "brain" of the computer.
In simple terms, the CPU is the chip that does the actual thinking.
RAM (Random Access Memory)
Temporary memory the computer uses while programs are running. Data in RAM is lost when the machine powers off.
Think of it as your desk: it holds whatever you are working on right now, but it gets cleared when you leave.
Binary
A base-2 number system that uses only two digits, 0 and 1.
In simple terms, binary is the language computers speak natively, because their circuits can only be on or off.
Bug
An error in code that causes a program to behave incorrectly or crash.
Debugging
The process of finding and fixing bugs in code.
Computer science is broad. The eight areas covered in this lecture are:
Programming – writing instructions a computer can execute
Data structures – organising and storing data so it can be accessed efficiently
Algorithms – step-by-step problem-solving procedures
Cybersecurity – protecting systems and data from attacks
Artificial intelligence – building systems that can learn, reason, or make decisions
Networking – connecting computers so they can communicate
Databases – storing, retrieving, and managing large collections of data
Software engineering – designing, building, and maintaining software systems at scale
Computers are built from transistors that have two states: on and off. Binary maps directly to those two states.
ON = 1
OFF = 0
Every piece of data a computer processes, whether text, images, or video, is ultimately represented as a string of 0s and 1s.
Decimal-to-binary examples:
Decimal 5 = Binary 101
Decimal 8 = Binary 1000
To convert, divide by 2 repeatedly and read the remainders from bottom to top.
Computers have gone through four major hardware generations:
Vacuum tubes (1940s) – large, power-hungry, unreliable; used in the earliest electronic computers
Transistors (1950s) – smaller, faster, and more reliable than vacuum tubes
Integrated circuits (1960s) – many transistors on a single chip, enabling miniaturisation
Microprocessors (1970s to present) – an entire CPU on one chip; the basis of every modern computer
Moore's Law is the observation that computing power roughly doubles every two years. It has held approximately true for decades, though it is now showing signs of slowing.
A computer does exactly what its instructions say, nothing more and nothing less. If the instructions contain an error (a bug), the computer will faithfully execute the wrong thing. Debugging is the process of finding and correcting those errors.
Binary is not just a textbook concept. Every file on your phone, every pixel on your screen, and every character in a text message is stored as a binary number. Understanding binary helps you grasp why file sizes are measured in bytes (groups of 8 bits) and why storage capacities come in powers of two.
Moore's Law explains why the smartphone in your pocket is millions of times more powerful than the computers that guided the Apollo missions to the moon.
Students often think "computer science" and "programming" are the same thing. Programming is one area within computer science, but the field also covers theory, hardware, security, data, and more.
Students sometimes believe binary is something only low-level engineers deal with. In fact, every higher-level concept (variables, data types, memory) is built on top of binary.
Moore's Law is sometimes treated as a physical law of nature. It is an empirical observation, not a guarantee, and the rate of improvement has been slowing in recent years.
"Bug" does not mean the computer made a mistake. The computer did exactly what it was told. The mistake belongs to the person who wrote the instructions.
⚠️ Know the definition of computer science and be able to name the eight main areas.
⚠️ Be able to convert small decimal numbers to binary by hand (divide-by-2 method).
⚠️ Understand why computers use binary (two-state electrical signals).
⚠️ Know the four generations of computer hardware in order, with approximate decades.
⚠️ Be able to state Moore's Law in your own words.
⚠️ Understand the difference between hardware and software, and between a bug and debugging.
True or false: Computer science is only about programming.
Fill in the blank: The base-2 number system is called ________.
True or false: RAM retains its data when the computer is turned off.
Fill in the blank: The four generations of computers are vacuum tubes, transistors, integrated circuits, and ________.
True or false: A bug is a mistake made by the computer, not the programmer.
Q: Define computer science in one sentence.
A: Computer science is the study of computers, algorithms, software, and how data is processed and stored.
Q: Why do computers use binary rather than decimal?
A: Because computer hardware is built from transistors that have two states (on and off), which map directly to 1 and 0.
Q: Convert the decimal number 5 to binary.
A: 101.
Q: List the four generations of computer hardware in order.
A: Vacuum tubes (1940s), transistors (1950s), integrated circuits (1960s), microprocessors (1970s to present).
Q: What is Moore's Law?
A: The observation that computing power roughly doubles every two years.
Q: What is the difference between a bug and debugging?
A: A bug is an error in code. Debugging is the process of finding and fixing that error.
Q: Name three of the eight main areas of computer science covered in this lecture.
A: Any three of: programming, data structures, algorithms, cybersecurity, artificial intelligence, networking, databases, software engineering.
This material connects directly to Lecture 2 (Introduction to Programming), where you will start writing actual code. The concepts of binary and hardware underpin how variables are stored in memory, which comes up as soon as you begin programming. Understanding the CPU and RAM distinction is essential when you reach data structures and algorithms later in the course.
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