what is overlay

In a general computing sense, overlaying refers to the process of transferring a block of program code or other data into main memory, replacing what is already stored. It is a programming method that allows programs to be larger than the computers main memory. This is particularly useful in embedded systems due to the limitation of physical memory and the lack of virtual memory facilities). Overlay can also refer to laying or spreading one thing over or upon another, covering, overspreading, or surmounting with something. Additionally, in the context of networking, an overlay network is a virtual or logical network created on top of an existing physical network. It enables traffic to be programmatically directed through new virtual network routes or paths instead of requiring physical links, allowing administrators to define and manage traffic flows irrespective of the underlying physical infrastructure. Furthermore, in the realm of portfolio management, overlay refers to an asset management style that uses software to harmonize an investors separately managed accounts. The overlay system analyzes any portfolio adjustments to ensure the overall portfolio remains in balance and to prevent any inefficient transactions from occurring.