Computer architectures represent the means of interconnectivity for the hardware components of a computer, as well as the mode of data transfer and processing exhibited. Different computer architecture configurations have been developed to speed up the movement of data, allowing for more data processing. The basic architecture has the CPU at the core with a main memory and an input / output system on each side of the CPU (see Figure 1.7). A second computer configuration is the central I / O controller (see Figure 1.8). A third computer architecture uses main memory as the location in the computer system from which all data and instructions flow. A fourth computer architecture uses a common data and control bus to interconnect all the devices that make up a computer system (see Figure 1.9). An enhancement to the single shared core bus architecture is the dual bus architecture. This architecture separates the data and control of the two buses or shares it to increase overall performance.