Quad-core processor

A quad-core processor is a processor or you can say that a quad core processor is a chip with four independent units called cores that read and execute the instructions given by the central processing units CU.
Within the chip, each core operates in collaboration with other units such as cache, memory management, and input/output ports. The individual cores that is one single core in a quad-core processor can run multiple instructions at the same time, increasing the overall speed for programs execution. Manufacturers typically integrate the cores onto a single semiconductor wafer, or onto multiple semiconductor wafers within a single integrated circuit  package.
Although it's very interesting  to suppose that a quad-core processor would operate twice as fast as a dual-core processor and four times as fast as a single-core processor because in a dual core processor there are two cores whereas in a single core processor there is only one core, things don't work out that simply. Results depend on the habits of the computer user, the nature of the programs being run, and the compatibility of the processor with other hardware in the system as a whole. so this means that its not necessary that if a single program takes a few nanoseconds to execute on single core processor than it should take half time to execute on a dual core processor and one fourth time on a quad core processor or so on. The execution of a program depends on the nature of the program being run and many other factors
Quad-core and higher multi-core processor  configurations have become common for general-purpose computing, not only for PCs but for mobile devices such as smartphones and tablets.