A1 Computer fundamentals

Introduction

Computer fundamentals explains what happens inside a computer between a key being pressed and a result appearing on the screen. It covers the physical parts that store and process data, the binary codes and logic those parts work with, the operating system that shares the hardware between programs, and, at HL, the translators that turn a program's source code into instructions a processor can carry out.

Every later topic rests on this picture. A network carries the same binary data that the central processing unit (CPU) processes, a database lives on secondary storage, machine learning models train on graphics processors, and every Python or Java program finally runs as machine code. Knowing how the hardware works also explains its limits: why a number can overflow its bits, why a program slows down when memory runs short, and why repeated access to the same data is faster than the first.

How the subtopics connect

The four subtopics form layers, each built on the one below it. At the bottom, subtopic A1.2, Data representation and computer logic, shows how integers, text, images and sound are stored in binary and how logic gates combine bits to compute results. Subtopic A1.1, Computer hardware and operation, builds the machine from those parts: the CPU's units, registers and buses, the fetch–decode–execute cycle, primary and secondary memory, compression, and cloud computing services.

Subtopic A1.3, Operating systems and control systems, sits above the hardware. The operating system (OS) manages memory, files, devices and security, schedules processes on the CPU and responds to interrupts; at HL it also covers multitasking, deadlock and the control systems that read sensors and drive motors. Subtopic A1.4, Translation, completes the stack at HL: a compiler, an interpreter or a just-in-time compiler turns source code into machine code, which the OS loads and runs as a process.

Subtopics at SL and HL

Three of the four subtopics are studied at both levels, but two of them contain statements that only HL students study. HL students study those extra statements inside the SL pages, where each one has a heading marked "(HL only)" and opens with an HL box. SL students can pass over those sections without missing anything the SL statements need.

The split inside A1.1 is narrow. SL students still learn what a GPU does and how the fetch–decode–execute cycle works; only the detailed CPU–GPU comparison and pipelining are HL.

Links to other topics

Ideas from computer fundamentals reappear across the course. Binary and hexadecimal from subtopic A1.2 return in IP and MAC addresses in topic A2, Networks, and in the data types and overflow errors of topic B2, Programming. Cloud computing is the starting point for digital infrastructure in subtopic A2.1, and secondary storage holds the databases of topic A3.

Control systems also raise a question of harm. When software reads sensors and moves physical equipment such as brakes or valves, a design error can injure people, which ties subtopic A1.3 to the ethical discussions of subtopic A4.4, Ethical considerations.