01
Abstraction Layers
A modern computer can be studied from digital logic through microarchitecture, instruction-set architecture, operating systems, runtime environments, and applications.
- Logic gates implement Boolean operations.
- Combinational and sequential circuits form digital components.
- Processor datapaths execute instructions.
- Memory systems store state across multiple performance levels.
- Instruction-set architectures define a programmer-visible machine model.
02
Memory Hierarchy
Computer memory is hierarchical because fast storage is expensive and limited while slower storage can be larger and cheaper.
- Registers.
- CPU caches.
- Main memory.
- Persistent storage.
- Remote or networked storage.
03
Performance
execution time = instruction count × cycles/instruction × seconds/cycle
Performance depends on architecture, instruction mix, memory behavior, parallelism, compiler decisions, workload characteristics, and I/O.