Computer hardware

Computer hardware refers to the physical, tangible components of a computing system.

These parts include the central processing unit (CPU), random-access memory (RAM), and the motherboard. Other essential parts include data storage, graphics cards, and sound cards. Hardware also includes external devices like monitors, mice, keyboards, and speakers. The term "hardware" comes from the fact that these parts are rigid and difficult to change. In contrast, software consists of written instructions that tell the hardware how to act. A functional computing system requires a combination of both hardware and software.

Modern computing relies on a specific design called the von Neumann architecture.

Devised by John von Neumann in 1945, this template is used by most modern computers. It features a centralized memory that stores both data and programs. A CPU is given priority to access this memory to perform tasks. The system uses a single bus to transfer data between these components. However, because programs and data are located adjacent to each other, a problem called the Von Neumann bottleneck can occur. This happens when the system tries to fetch both at the same time, which can throttle performance.

Computer architecture involves a complex balance of several competing goals. Designers must weigh cost, speed, availability, and energy efficiency. Manufacturers also face significant cost constraints to remain competitive in the market. Interestingly, the cost of components has dropped over time even when performance stayed the same. This is due to improved manufacturing techniques that result in fewer rejected parts during quality assurance. To manage memory, computers use a hierarchy. This ensures that fast, expensive memory is located close to the CPU. Slower, cheaper memory is placed further away for large-volume storage.

Instruction set architecture (ISA) acts as the interface between hardware and software. Most common ISAs are based on von Neumann's 1945 designs. There are different types of ISAs, such as Complex Instruction Set Computer (CISC) and Reduced Instruction Set Computer (RISC). CISC uses a larger set of instructions to minimize the number of steps a machine must take. RISC simplifies the instruction set, which allows for more registers. After RISC was invented in the 1980s, it began to displace CISC in many areas. This was especially true for devices with power or space limits, such as mobile phones.

Computing history began long before the digital age. In 1642, Blaise Pascal designed the Pascaline, a gear-based device for addition and subtraction. In 1676, Gottfried Leibniz invented the stepped reckoner, which could also multiply and divide. In the 19th century, Charles Babbage designed the mechanical difference engine to calculate polynomials. Babbage also designed a general-purpose computer that was never built. His designs included early versions of memory and arithmetic units. In 1936, Alan Turing developed the concept of the universal Turing machine. This model demonstrated how a machine could mimic any operation based on software instructions.

Between 1986 and 2003, hardware performance improved at an incredible rate. The annual improvement rate exceeded 50 percent during this period. This rapid growth enabled the creation of tablets and mobile devices. During this time, DRAM memory and flash storage also became much smaller and cheaper. In the 21st century, performance increases have shifted toward exploiting parallelism. This means performing multiple tasks or data functions simultaneously. Hardware strategies like graphics processing units (GPUs) help implement this data parallelism.

Hardware design also requires careful management of heat and power. Computer processors generate significant heat during operation. Excessive heat can harm components or reduce performance. To prevent this, many chips will automatically throttle their speed. Computers use cooling mechanisms like air coolers, liquid coolers, or heatsinks. Data centers often use advanced solutions like liquid-cooled immersion to keep temperatures safe. Power delivery and heat dissipation are now major limiting factors in chip development. As performance increases, the demand for energy and cooling also increases.

Computers exist in many different forms to suit different needs. Personal computers are versatile and include desktops and laptops.

Desktops use a case to hold the motherboard and power supply. Laptops are designed for portability and integrate the screen and keyboard into one unit. Tablets are even smaller and rely on touch screens for input. On a much larger scale, mainframes can fill entire rooms and serve large enterprises. Finally, supercomputers are designed for maximum performance in complex math. These machines can cost hundreds of millions of dollars.