Välimuistitieto

Välimuistitieto, often referred to as cache, is a temporary storage area that holds frequently accessed data from a primary storage system, such as main memory or a disk. The purpose of cache is to speed up data retrieval by reducing the need to access slower, primary storage. When a program or device needs data, it first checks the cache. If the data is present in the cache, known as a cache hit, it can be retrieved very quickly. If the data is not found in the cache, known as a cache miss, it must be fetched from the slower primary storage and then copied into the cache for future use.

Caches are employed in various levels of computing, from hardware components like CPUs and hard drives to software applications and web browsers. CPU caches are small, extremely fast memory chips located on or near the processor that store instructions and data the CPU is likely to need next. Web browser caches store copies of website elements, such as images and HTML files, to reduce loading times on subsequent visits. The management of cache, including deciding what data to store and when to remove it, is handled by specific algorithms designed to maximize hit rates and minimize performance degradation. The size and speed of a cache directly impact the performance of the system it serves.