A central processing unit (CPU) is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logical, control and input/output operations specified by the instructions. The term has been used in the computer industry at least since the early 1960s.
The form, design, and implementation of CPUs have changed over the course of their history, but their fundamental operation remains much the same. Principal components of a CPU include the arithmetic logic unit (ALU), which performs arithmetic and logical operations, and the control unit(CU), which fetches instructions from memory and decodes and executes them, calling on the services of the ALU when necessary.
Most modern CPUs are microprocessors, meaning they are contained on a single integrated circuit (IC) chip. Some computers have two or more CPUs on a single chip and thus are capable of multiprocessing; these are called multi-core processors. An IC that contains a CPU may also contain memory, peripheral devices, and other components of a computer; such devices are variously called microcontrollers or system on a chips (SoC).
Not all computational systems employ central processing units. For example, an array processor or vector processor has multiple parallel computing elements, with no one unit considered "central".
The Imitation Game
Alan Mathison Turing, OBE, FRS (/ˈtjʊərɪŋ/ tewr-ing; 23 June 1912 – 7 June 1954) was a British mathematician, logician, cryptanalyst, philosopher, pioneering computer scientist, mathematical biologist, and marathon and ultra distance runner. He was highly influential in the development of computer science, providing a formalisation of the concepts of "algorithm" and "computation" with the Turing machine, which can be considered a model of a general purpose computer. Turing is widely considered to be the father of theoretical computer science andartificial intelligence.
During World War II, Turing worked for the Government Code and Cypher School (GC&CS) at Bletchley Park, Britain's codebreaking centre. For a time he led Hut 8, the section responsible for German naval cryptanalysis. He devised a number of techniques for breaking German ciphers, including improvements to the pre-war Polish bombe method, an electromechanical machine that could find settings for the Enigma machine. Winston Churchill said that Turing made the single biggest contribution to Allied victory in the war against Nazi Germany. Turing's pivotal role in cracking intercepted coded messages enabled the Allies to defeat the Nazis in several crucial battles. It has been estimated that Turing's work shortened the war in Europe by as many as two to four years.
After the war, he worked at the National Physical Laboratory, where he designed the ACE, among the first designs for a stored-program computer. In 1948 Turing joined Max Newman's Computing Laboratory at Manchester University, where he assisted development of theManchester computers and became interested in mathematical biology. He wrote a paper on the chemical basis of morphogenesis, and predicted oscillating chemical reactions such as the Belousov–Zhabotinsky reaction, first observed in the 1960s.
Turing was prosecuted in 1952 for homosexual acts, when such behaviour was still criminalised in the UK. He accepted treatment withoestrogen injections (chemical castration) as an alternative to prison. Turing died in 1954, 16 days before his 42nd birthday, from cyanidepoisoning. An inquest determined his death a suicide; his mother and some others believed it was accidental. In 2009, following an Internet campaign, British Prime Minister Gordon Brown made an official public apology on behalf of the British government for "the appalling way he was treated." The Queen granted him a posthumous pardon in 2013.[
Random-access memory (RAM /ræm/) is a form of computer data storage. A random-access memory device allows data items to be read and written in roughly the same amount of time regardless of the order in which data items are accessed. In contrast, with other direct-access data storage media such as hard disks, CD-RWs, DVD-RWs and the older drum memory, the time required to read and write data items varies significantly depending on their physical locations on the recording medium, due to mechanical limitations such as media rotation speeds and arm movement delays.
Today, random-access memory takes the form of integrated circuits. RAM is normally associated with volatile types of memory (such as DRAMmemory modules), where stored information is lost if the power is removed, although many efforts have been made to develop non-volatile RAM chips. Other types of non-volatile memory exist that allow random access for read operations, but either do not allow write operations or have limitations on them. These include most types of ROM and a type of flash memory called NOR-Flash.