Hardware Foundations: CPU and Memory

Central Processing Unit

The CPU (Central Processing Unit) is the computation and control core of a computer system and executes program instructions.

Its core components include:

• Control unit (CU): fetches and decodes instructions and coordinates processor operations.
• Arithmetic-logic unit (ALU): circuits that perform arithmetic and logical operations.
• Registers: small, high-speed storage components that temporarily hold instructions, data, and addresses.

Fetch, Decode, Execute

Instruction processing in most modern processors can be described as a fetch-decode-execute cycle. The von Neumann architecture is a stored-program architecture with a shared instruction/data memory system, not another name for the instruction cycle.

CPU Information

Python's multiprocessing module can report the system's logical CPU count.

import multiprocessing

print(f"System logical CPUs: {multiprocessing.cpu_count()}")

Python's psutil module also provides system hardware information.

import psutil

physical = psutil.cpu_count(logical=False)
logical = psutil.cpu_count(logical=True)
times = psutil.cpu_times()

print(f"Physical cores: {physical if physical is not None else 'unknown'}")
print(f"Logical CPUs: {logical if logical is not None else 'unknown'}")
print(f"CPU time (user): {times.user:.2f} seconds")
print(f"CPU time (system): {times.system:.2f} seconds")
print(f"CPU time (idle): {times.idle:.2f} seconds")

Storage Units

Storage units include bit (b), B, kB, MB, GB, TB, PB, EB, ZB, and YB.

A bit is the smallest storage unit and holds one binary digit.

A byte contains eight bits. An English letter in ASCII takes one byte; a Chinese character's byte count depends on encoding, with common Chinese characters taking three bytes in UTF-8. A word is an architecture-dependent data unit, not a synonym for a Chinese character.

Disk manufacturers commonly use decimal units, with 1000 bytes per kB. These are standard units, not fraudulent accounting.

Storage Devices and the Memory Hierarchy

Storage devices preserve digital information using electrical, magnetic, or optical media. The hierarchy includes registers, CPU cache, main memory, SSDs, hard disks, optical disks, and magnetic tape. Higher levels are generally faster, smaller, and more expensive per bit.