Fundamentals of computer systems

Fundamentals of computer systems is the bedrock of AQA A-Level Computer Science, covering how hardware and software interact to form a functional computing device. This topic explores the von Neumann architecture, the fetch-execute cycle, and the role of system software like operating systems and translators. Understanding these principles is crucial because they explain how programs are stored, processed, and executed, forming the foundation for more advanced topics such as computer organisation, networking, and programming paradigms.

At its core, this topic demystifies what happens inside a computer when you run a program. You'll learn about the CPU's components—ALU, control unit, registers (PC, MAR, MDR, CIR, ACC)—and how they work together to fetch, decode, and execute instructions. The concept of stored program control, where both data and instructions are held in memory, is central. This knowledge is not just theoretical; it helps you debug code, optimise performance, and understand limitations like the von Neumann bottleneck.

This topic also introduces the layered model of computer systems: from hardware (CPU, memory, I/O) to system software (OS, utilities) and application software. You'll explore how the OS manages resources, provides a user interface, and handles file management. Translators (assembler, compiler, interpreter) are covered, highlighting the journey from high-level code to machine code. Mastery of these fundamentals is essential for tackling later topics like data representation, networks, and databases, making it a cornerstone of the A-Level course.