3Do a shut down/reboot also known as a cold reboot. Some programs do not release memory properly when they close, which is the case for some operating systems. Even doing a warm restart will not release some of the memory drivers and other core programs had allocated. The computer has to be completely shut down and then restarted.
When a program is asking for some memory, a space would be allocated for it by the operating system (like Windows). This allocated memory can not be used by any other programs. "Well-behaved" programs typically let go of their hold of this memory space but some programs don't - this is known as a "memory leak", which is caused by a programming error.
A memory leak is easily evident when a program uses up an abnormally high amount of resources because it keeps on asking for more and never gives back any of the allocated memory space. The user workaround is to terminate the program or process, but some processes and core processes can not be closed. Shutting down the system will have the operating system forget which memory locations aren't free, so on the next boot, all memory locations are free to use.
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