The control unit (often called a control system or central controller) manages the various components of the computer. It reads and interprets (decodes) program instructions and converts them into control signals that activate other parts of the computer. [95] Control systems on advanced computers can change the order in which certain instructions are executed to improve performance. A computer`s memory can be displayed as a list of cells into which numbers can be inserted or read. Each cell has a numbered “address” and can store only one number. The computer may be prompted to “enter the number 123 in the cell with the number 1357” or “add the number that is in cell 1357 to the number in cell 2468 and enter the response in cell 1595.” Information stored in memory can represent virtually anything. Letters, numbers and even computer instructions can be placed in memory with the same ease. Since the processor does not distinguish between different types of information, it is the responsibility of the software to attach importance to what the memory considers to be nothing more than a series of numbers. System-on-a-chip (SoCs) are complete computers on a microchip (or chip) the size of a coin. [91] They may or may not have built-in RAM and flash memory. If not integrated, RAM is usually placed directly above (known as Package on Package) or below (on the other side of the PCB) of the SoC, and flash memory is usually placed right next to the SoC, all to improve data transfer speeds because data signals don`t have to travel long distances. Since the ENIAC in 1945, computers have evolved enormously, with modern SoCs (like the Snapdragon 865) the size of a coin, but also a hundred thousand times more powerful than the ENIAC, integrating billions of transistors, and consuming only a few watts of power. The first calculating machines had fixed programs.
The change in its function required the rewiring and restructuring of the machine. [30] This changed with the proposal of the memory program computer. A computer with recorded programs contains a default set of instructions and can store in memory a set of instructions (a program) that describes the calculation in detail. The theoretical basis of the memory program computer was laid by Alan Turing in his work in 1936. In 1945, Turing joined the National Physics Laboratory and began developing a digital computer for electronic memory programs. His 1945 report “Proposed Electronic Calculator” was the first specification for such a device. John von Neumann of the University of Pennsylvania also circulated his first draft of a report on the EDVAC in 1945. [20] Before the era of inexpensive computers, the main advantage of multitasking was that it allowed many people to share the same computer. Apparently, multitasking would result in a computer moving from one program to another slower, in direct proportion to the number of programs it runs, but most programs spend much of their time waiting for slow input/output devices to do their job.
When a program waits for the user to click the mouse or press a key on the keyboard, it does not take a “time slot” for the event it is waiting for to occur. This gives time for other programs to run, so many programs can run at the same time without unacceptable loss of speed. The means by which the computer provides the output are called output devices. Here are some examples of output devices: Charles Babbage, an English mechanical engineer and polymath, developed the concept of a programmable computer. As the “father of the computer”[17], he designed and invented the first mechanical computer in the early 19th century. After working on his revolutionary difference engine to help with navigation calculations, he realized in 1833 that a much more general design, an analytical engine, was possible. The entry of programs and data had to be made available to the machine via punched cards, a method by which mechanical looms such as the jacquard loom were controlled at the time. For output, the machine would have a printer, a curve plotter and a bell. The machine would also be able to punch numbers on cards for later reading.
The engine included an arithmetic unit of logic, a flow of control in the form of conditional branches and loops, and built-in memory, making it the first design of a general-purpose computer that could be called Turing-complete in modern terms. [18] [19] The metal-oxide-silicon field effect transistor (MOSFET), also known as the MOS transistor, was invented by Mohamed M.
