The document summarizes the basic functional units and operations of a computer system. It describes how a computer contains a central processing unit (CPU) that includes an arithmetic logic unit (ALU) and control unit to execute instructions. A computer also has memory to store programs and data, and input/output (I/O) devices to accept and output information. The CPU fetches instructions from memory, retrieves operands from memory or registers, performs operations in the ALU, and stores results back to memory or registers. The control unit coordinates the flow of data and execution of instructions. Performance can be improved by increasing clock speed, reducing the number of steps per instruction through pipelining and superscalar techniques, and optimizing compilers