What Is a Central Processing Unit (CPU)?

Key takeaways

A central processing unit (CPU) is the main processor that runs a computer's applications and operating systems.

• A CPU operates on a three-step instruction cycle using binary code to process instructions stored in memory.

• Modern CPUs combine multiple cores with technologies like hyperthreading, which splits each core into two virtual threads to handle more processes simultaneously.

• You can pursue a career in building and maintaining computer hardware by becoming a computer hardware engineer.

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What is a central processing unit?

The central processing unit, also known as a CPU, processor, microprocessor, or computer processor, is a small yet crucial piece of hardware found in computing devices such as desktops, smartphones, tablets, and TVs. The CPU is found within a device's motherboard and contains microscopic switches that manage how electricity flows throughout its circuits.

Central processing unit definition

A central processing unit is the main processor that has the ability to run a machine's applications and operating systems. Since the CPU is in control of the operations of a computer, it’s commonly referred to as the “brain” of the computer.

What does CPU stand for? Does CPU mean RAM?

No, CPU does not mean RAM. The CPU, also known as the processor, gives the computer instructions to perform. On the other hand, RAM is what the computer uses for temporary storage space. The CPU and RAM work together and are important for giving you computing power.

What does a central processing unit do?

A CPU uses binary, or machine language, to decode instructions it receives from memory. From there, the CPU can execute the instructions and store that information for later use in the device's memory. This means the CPU is regularly working with the random access memory (RAM) to store and deliver instructions for the CPU. Here is how a CPU works in a three-step instruction cycle: 

Step 1: Fetch

The CPU first must fetch instructions stored within the computer's RAM. A component of the CPU known as the instruction register stores the instructions.

Step 2: Decode

In order to determine what actions to perform, the CPU transfers instructions from the instruction register to the instruction decoder, where it performs a calculation to decode the instruction into signals.

Step 3: Execute

During the final step, the decoded signal travels to specific locations in the CPU, allowing the CPU to execute the desired action. The instruction process repeats itself automatically as the CPU moves on to the next task.

Central processing unit computer architecture

A CPU typically consists of multiple components, including the following:

• Registers: Registers are a specific type of permanent memory found directly within the CPU that stores and transfers data quickly, as opposed to RAM or cache memory.

• Buses: Buses are small wires that behave as an interface to memory or a highway where data can travel between components.

• Control unit: The control unit oversees instruction processing and orchestrates data flow within the CPU and among other computer components.

• Arithmetic logic unit: The arithmetic logic unit (ALU) performs arithmetic and logical operations on data, drawing input from CPU registers and adhering to instructions from the control unit.

• Clock: The CPU's intricate circuit requires precise synchronization, facilitated by its clock, which issues electrical pulses at regular intervals, aligning with various computer components. 

• Cache: The CPU doesn't access RAM directly; instead, contemporary CPUs rely on one or more layers of cache memory. The cache, faster than RAM and positioned closer to the processor chip, stores data and instructions.

Learn more: Information Technology (IT) Terms: A to Z Glossary

Devices that use CPUs

A CPU is in almost every electronic device that needs to process information to function, including all kinds of computers and smart devices. Some examples of things that use CPUs include:

• Computers

• Laptops

• Tablets

• Smartphones

• Flat-screen TVs

• Digital cameras

• Thermostats

• Smartwatches

• Computer-aided design (CAD) systems

Types of CPUs

The different types of CPUs depend on the number of cores they have, including:

• Single-core processors

• Dual-core processors 

• Quad-core processors

• Hexa-core processors

• Octa-core processors

• Deca-core processors

Cores are the processors of the CPU, and most CPUs contain at least two. Having more cores allows a CPU to complete multiple tasks simultaneously, increasing a computer's overall speed and efficiency. 

A downside of having a large number of cores is that it requires increased power consumption and has the potential to overheat. Although computers with fewer cores may lack the same speed and efficiency as multi-core devices, the lower power consumption helps to enable proper functionality. 

What is CPU clock speed?

The clock speed, or clock rate, is measured in gigahertz and describes how fast a CPU processes data within any given second. For example, a CPU with a clock speed of 4.0 GHz can process 4 billion instructions, or cycles, per second. Along with the number of cores, clock speed helps to indicate how well a CPU performs, with a higher clock speed generally implying a greater level of performance. 

However, the number of cores or clock speed alone isn’t enough to determine whether one CPU is necessarily better than another because it also depends on the type of software or applications running on the device. Similarly, as a higher number of cores has the potential to produce more heat, a higher clock speed has the same effect. That said, processors can mitigate this by lowering clock speed when they get too warm. 

How hyperthreading enhances the pace of CPU processing

Another way to improve the performance of CPUs is through a technology called hyperthreading. It's an advancement to CPUs that enables a single core to process information faster as if it had the power of two cores. Hyperthreading divides information into multiple threads, allowing the core to process the threads simultaneously. Developed by Intel, hyperthreading allows an individual core to act like it has multiple cores working simultaneously, resulting in a computer that processes larger amounts of information in less time.

It splits each core into two virtual cores known as threads. Hypothetically, if your computer has a dual-core CPU, hyperthreading enables you to have four virtual cores, allowing the device to handle more demanding applications and complete a greater number of processes at the same time.

Related terms

• Motherboard

• BIOS

• Operating system

• Binary code

• IT infrastructure

Who designs and builds CPUs?

Computer hardware engineers design and develop a computer's various physical components and systems, including its memory and processors. This process involves significant testing to determine how the components work together to ensure compatibility. Hardware engineering positions exist beyond computer and phone manufacturing, such as in the health care, automotive, airline, and telecommunications industries.

How to get started in computer hardware engineering

To become a computer hardware engineer, you usually need to earn a bachelor’s degree in computer engineering or a related field, such as information technology, electrical engineering, or computer science. In some cases, companies may also require you to have a master’s degree in computer hardware engineering. 

Completing an internship is a great way for you to supplement your education and gain valuable experience working with computer hardware components, as are certifications. Useful certifications for hardware engineers include CompTIA A+ and Cisco Certified Technician (CCT).

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