Exascale Computing Architecture and Software is a comprehensive framework for designing and implementing computing systems capable of executing quintillion (10^18) floating-point operations per second — Exascale computing represents the frontier of high-performance computing, enabling simulations of complex phenomena including climate modeling, nuclear fusion, and molecular dynamics at unprecedented fidelity. Hardware Architecture implements heterogeneous systems combining CPUs, GPUs, and specialized accelerators, requiring 50-100 megawatts of power while maintaining reasonable footprints through efficient power distribution. Processor Design balances compute density, memory bandwidth, and power efficiency through advanced silicon process nodes, specialized instruction sets, and integrated accelerators. Memory Architecture implements multi-level hierarchies including local processor caches, shared memory pools, and distributed global memory, addressing bandwidth limitations that often dominate performance. Interconnect Fabric employs high-speed networks like Dragonfly topologies providing low-latency communication, enabling efficient all-to-all communication patterns. Software Stack requires complete redesign addressing massive parallelism, including new programming models, runtime systems, and compilers. Resilience addresses failures inevitably occurring in systems with millions of components, implementing checkpoint-restart, error correction, and fault tolerance mechanisms. Power Management exploits dynamic voltage and frequency scaling, idle component power gating, and workload balancing distributing computation load. Exascale Computing Architecture and Software demands holistic innovation across hardware, software, and algorithms.