Of daily use, a computer is an electronic equipment, already almost considered an appliance, generally associated to a monitor, a keyboard and a mouse. He/she is becoming also more and more desirable for the users of computers to possess some connection form to the Internet.
Computers can be used for the fingering of texts, storage of information, processing of data, communication writing or spoken or for entertainment. Finally, it is limitless the number of tasks that he can carry out. They are tools that get to be applied in more several tasks to every day, and if turning more and more indispensable.
In the widest sense, a computer is any equipment or device capable to store and to manipulate, logic and mathematically, numeric amounts represented physically. Examples of computers: abacus, calculator, analog computer, digital computer. The first machines of computing Pascaline, calculating machine done by Blaise Pascal to Enlarge Pascaline, calculating machine done by Blaise Pascal John Napier (1550-1617), Scottish inventor of the logarítmos, also invented the bones of Napier, that were multiplication tables recorded in stick, what avoided the memorization of the tabuada.
The first machine was really built by Wilhelm Schickard (1592-1635), being capable to add, to subtract, to multiply and to divide. That machine was lost during the the 30 year-old war, and recently some was found documentation on her. For many years anything one knew about that machine, that, Blaise Pascal was attributed (1623-1662) the construction of the first calculating machine, that just made sums and subtractions.
The machine of Pascal was created with objective of helping the father of Pascal to compute the taxes in Rouen, France.
The project of Pascal was plenty of aprimorado for a German mathematician, that also invented the calculation, called Gottfried Wilhelm Leibniz (1646-1726), which dreamed that, one day in the future, all the reasoning could be substituted by rotating of a simple lever. We will speak more on that subject in the future.
All those machines, even so, they were far away from being a computer of general use, because they were not programmable. This means that the entrance was just made of numbers, but not of instructions regarding what to do with the numbers. The origin of the idea of programming a machine comes from the need that the machines of weaving produced patterns of different colors. Thus, in the century XVIII a form was created of representing the patterns in cards of perforated paper, that were negotiated manually. In 1801, Joseph Marie Jacquard (1752-1834) it invents a mechanical tear, with an automatic reader of cards.
The machine of weaving of Jacquard worked so albeit thousands of tecelões lost the employment with the automation, if rebelling and almost killing the inventor.
Jacquard's idea crossed the Channel of the Stain, where it inspired Charles Babbage (1792-1871), a teacher of mathematics of Cambridge, to develop a machine of “to weave numbers”, a machine of calculating where the form of calculating could be controlled by cards.
Everything began with the attempt of developing a machine capable to calculate polynomials by means of differences, the calculating diferencial. While it projected its calculating diferencial, Jacquard's idea he/she did with that Babbage imagined a new and more complex machine, the analytic calculator. This machine was extremely similar to the current computer.
Its main part would be a group of jagged wheels, the mill, forming a machine of adding accurately of 50 digits. The instructions would be read of perforated cards. The cards would be read in an entrance device and stored, for future references, in a bank of 1000 registrars.
Each one of the registrars would be capable to store a number of 50 digits, that you/they could be placed there by means of cards starting from the result of one of the calculations of the mill.
Besides everything, Babbage imagined the first impression machine, that would print the results of the calculations, contained in the registrars.
Babbage got, during some time, funds for its research, even so it didn't get to complete its machine in the promised time and it didn't receive more money. Today, parts of its machine can be seen in the British Museum, that it also built a complete version, using the available techniques at that time.
With Babbage, he/she worked young August Ada, the poet's Lord Byron daughter, known like Lady Lovelace, or Ada Lovelace. Ada was the first programmer of the history, projecting and explaining, at the request of Babbage, programs for the nonexistent machine. Ada invented the subrotina concepts, a sequence of instructions that it can be used several times, loop, an instruction that allows the repetition of a sequence of cards, and of the conditional jump, that allows to jump some card in case a condition is satisfied.
Ada Lovelace and Charles Babbage were too advanced for its time, so much that until the decade of 1940, anything he/she/it invented similar to its analytic computer. Until that time they were built many mechanical machines of to add destined to control business (mainly cash registers) and some machines inspired by the calculator diferencial of Babbage, to accomplish engineering calculations (that didn't reach great success). The next progress of the computers was made by American Herman Hollerith (1860-1929), that invented a machine capable to process data based on the separation of perforated cards (for its holes). The machine of Hollerith was used to aid in the census of 1890, reducing the time of processing of 7 year-old data, of the previous census, for just 2 and a half years. The machine of Hollerith also went pioneer when using the electricity in the separation, contagem and tabulation of the cards.
The company founded by Hollerith is known today like International Bussiness Machines, or IBM. The first computer eletro-mechanic was built by Konrad Zuse (1910–1995). In 1936, that German engineer built, starting from relês that executed the calculations and data read in perforated ribbons, the Z-1. Zuse tried to sell the computer Z 1 to the German government, that despised the offer, since it could not aid in the war effort... The projects of Zuse would be stopped during the war, giving the chance to the Americans of developing its computers.
It went in to II World War that were really born the current computers. The American Navy, together with the University of Harvard, it developed the computer Mark I, projected by teacher Howard Aiken, with base in the analytic calculator of Babbage. Mark I occupied 120 m3 approximately, getting to multiply two numbers of 10 digits in 3 seconds.
Simultaneously, and secretly, the American Army developed a similar project, chefiado for engineers J. Presper Eckert and John Mauchy, whose result went the first computer to valves: Eletronic Numeric Integrator And Calculator: ENIAC. He was capable to do 500 multiplications a second! Having been projected to calculate ballistic trajectories, ENIAC was maintained secretly by the American government until the end of the war, and it was only announced for the world after the end of the war. ENIAC, computer developed by the American Army to Enlarge ENIAC, computer developed by the American Army In ENIAC, the program was made rearranging the fiação in a panel. In that point John von Neumann proposed the idea that transformed the electronic calculators in “electronic brains”: to model the architecture of the computer according to the central nervous system. For that, they would have to have 3 characteristics: 1. To code the instructions in a possible way of being stored in the memory of the computer. Von Neumann suggested that some and zeros were used.
2. To store the instructions in the memory, as well as all and any necessary information the execution of the task, and 3. When it processes the program, to look for the instructions directly in the memory, instead of they read a new card perforated to each step. This is the concept of Stored Program, whose main advantages are: speed, versatility and automodificação. Thus, the programmable computer that knew today, where the program and the data are stored in the memory it was well-known as von computer Neumann.
To disclose that idea, von Neumann it published alone an article. Eckert and Mauchy were not very happy with that, because they would have discussed a lot of times the idea with von Neumann. The project ENIAC finished dissolving in a rain of processes, but the modern computer was already created.
Nowadays, the computer is practically indispensable in the people's life, because, besides gathering generations, he can approach friends, relatives, besides being very useful for our life. Even if the technology used in the digital computers has moved dramatically from the first computers of the decade of 1940 (he/she sees History of the hardware), all the current computers almost use still the architecture of von Neumann proposal in the end of the decade of 1940 for John von Neumann. The von architecture Neumann describes the computer with four main sections: THE logical and arithmetic Unit (ULA), the Unit of control, the memory, and the entrance devices and exit (E/S or I/O). These parts are interconnected by threads and barramentos. The memory of the computer is usually divided between primary and secondary, being also possible to speak of a tertiary memory. The primary memory is directly that acessada for ULA. Traditionally that memory can be of reading and writing (RAM) or only of reading (ROM). Now they exist memoirses that they can be classified as reading preferencialmente, that it is, variations of the memory ROM that can be regravadas, even so with a limited number of cycles and a much higher time.
The primary memory usually communicates with ULA by means of a bus or channel of data.
The access speed the memory is an important factor of cost of a computer, that the primary memory is usually built in a hierarchical way in a computer project. It leaves of the memory, known as Memória Cachê it is very close to ULA, with very fast access. Most of the memory is acessada by means of auxiliary roads.
The memory is usually sharply separate from ULA in a computer architecture. Even so, the current microprocessors possess incorporated memory salary, what increases in a lot its speed. The memory RAM (Random Access Memory) it is a sequence of numbered cells, each one contends a small amount of information. The information can be an instruction to say to the computer that to do. The cells can also contain data that the computer needs to accomplish an instruction. Any cell can contain instruction or given, like this the one that in some moment it stored data it can store instructions in another moment.
In general, the content of a cell of memory can be altered any moment - THE memory RAM is a scratch and not a stone block.
The memoirses RAM genericamente of DRAM is denominated (RAM dynamics), for the fact of they possess a characteristic called refrescamento of memory, that has the purpose of maintaining the stored data while the computer be called.
The size of each cell, and the number of cells, varies of computer for computer, and the technologies used to implement the memory RAM they vary enough. Now the most common is the implementação in integrated circuits. The memory ROM (Read-Only Memory) it is a memory that can only be read and the data are not lost with the desligamento of the computer. The difference among the memory RAM and ROM are that RAM accepts recording, regravação and loss of data. Same if he/she is a correspondent an information to be recorded in the memory ROM, the procedure is not executed (this characteristic practically eliminates the virus creation that you/they affect ROM).
A software engraving in ROM receives the firmware name, they are basically three existent in that memory for a computer of the line IBM-PC, that you/they are acessados whole time that we tied the computer: * BIOS; * POST; * SETUP.
A variation of ROM call memory reading preferencialmente that allows the re-recording of data exists. They are the calls EPROM (Erasable Programmable Read Only Memory) or EEPROM (Electrically Erasable Programmable Read-Only Memory). The secondary Memory or Memory of Mass is used to record great amount of data, that they are not lost with the desligamento of the computer, for a long period of time. Examples of memory of Mass: * CD-ROM; * DVD; * hard disk; * Diskette.
The secondary memory is not usually directly acessada for ULA, but yes by means of the devices of Entrance and Exit. That does with that the access to that memory is much slower than the access the primary memory.
Supposedly, we considered that the tertiary memory is permanently linked to the computer. Systems more computation complexes can include a third level of memory, with access still slower than the one of the secondary memory. An example would be an automated system of ribbons contends the necessary information.
The tertiary memory is not nothing else than a device of secondary memory or mass memory placed to serve a device of secondary memory.
In the past, the term was already applied responsible people by some calculation.
In general, he/she understands each other for computer a physical system that accomplishes some computation type. It still exists the rigorous mathematical concept, used in the theory of the computation. The technologies of memory use materials and quite varied processes. In the computer science, they have always been developing in direction of a larger storage capacity, larger miniaturization, larger access speed and reliability, while its cost constantly drops.
However, the memory of a computer is not limited its individual and physical memory, she comes in a wider way, and without defined place (desterritorializada). We have possibilities to store in several places in the net, we can be in Luanda and acessar files that were stored in sites in Brazil.
It is growing the tendency for the storage of the information in the memory of the virtual, or called space him cyberspace, through virtual disks, enclosures of and-mails etc. Thus, texts, images, videos, audio files, among so many other formats, become available for the access of any computer connected to the Internet. The technologies of memory use materials and quite varied processes. In the computer science, they have always been developing in direction of a larger storage capacity, larger miniaturization, larger access speed and reliability, while its cost constantly drops.
However, the memory of a computer is not limited its individual and physical memory, she comes in a wider way, and without defined place (desterritorializada). We have possibilities to store in several places in the net, we can be in Luanda and acessar files that were stored in sites in Brazil.
It is growing the tendency for the storage of the information in the memory of the virtual, or called space him cyberspace, through virtual disks, enclosures of and-mails etc. Thus, texts, images, videos, audio files, among so many other formats, become available for the access of any computer connected to the Internet. ULA, is the device that makes the elementary operations (addition, subtraction and etc.), logical operations (AND, OR, NOT), and comparison operations (for example, to compare two bytes and to say if they are the same). It is in this unit that the " real " work is made.
The unit of control stores the position of memory that contains the average instruction that the computer is executing, informing ULA which operation to execute, looking for the information (of the memory) that precise ULA to execute it and transferring the turn result for the adapted place of the memory. Done this, the unit of control is going to the next instruction (typically located in the next position of the memory (address of memory), unless the instruction is a deviation instruction informing the computer that the next instruction is in another position). E/S allows to the computer to obtain information of the external world, and he/she sends the results of the work for the external world. An infinity of types of devices of E/S exists, of the relatives keyboards, monitors and drive of diskettes, until other less usual as webcams and plates of video capture (devices that capture video sequences or video frames and they store them in the computer).
The one that all the entrance devices have in common is that they need to code (to convert) the information of some type in data that can be processed by the digital system of the computer. Exit devices on the other hand, descodificam the data in information that is understood by the user of the computer. In this sense, a digital system of computers is an example of a system of processing of data.
We can have devices that work so much for entrance as for exit of data, the modem, the diskette drive among other, is examples of these devices. The instructions discussed above are not a rich group of instructions as the human language. The computer just has a limited number of very defined instructions. A typical example of an existent instruction in most of the computers is " it copies the content of the position of memory 123 for the position of memory 456 ", " add the content of the position of memory 510 to the content of the position 511 and place the result in the position 507 " and " if the content of the position 012 is the same to 0, the next instruction is in the position 678 ".
Instructions are represented in the computer as numbers - the code " to copy " could be 007, for example. The group peculiar of instructions that a computer possesses is known as the language of machine of the computer. In the practice, the people don't write instructions directly in the machine language but in a programming language, that is translated later on in the machine language through special programs (interpretadores and compilers). Some programming languages approach enough of the machine language, as the assembly (language of low level); on the other hand languages as Prolog is set in abstract beginnings and they go away enough of the details of the operation of the machine (languages of high level). In the modern computers, ULA and the unit of control they are in an only well-known integrated circuit like CPU (Central Processing Unit). Typically, the memory of the computer is located in few circuits integrated CPU close to. Most of the mass of a computer is owed to auxiliary systems (for example, the source of electric energy) or devices of E/S.
Some larger computers differ above of the model in a main aspect - they have multiple CPUs working simultaneously. Adicionalmente, few computers, used mainly for research and scientific computation, have significant differences of the model above, but they don't have great commercial application.
The operation of the computer follows the exposed rules basically. The computer looks for the instructions and the data of the memory, the instructions are executed, the stored results, and the next instruction is looked for. This I am processed he/she repeats until the computer to be turned off. Programs Programs are simply great lists of instructions for the computer to execute, perhaps with tables of data. Many computer programs contain millions of instructions, and many of these instructions are executed repeatedly. A typical personal computer (in the year of 2003) it could execute about 2-3 billion instructions a second. The computers don't have its extraordinary capacity due to a complex group of instructions. In spite of project differences they exist with CPU with a larger number of instructions and more complex, the computers execute millions of combined simple instructions, written by good " programmers ". These combined instructions are written to accomplish common tasks as, for example, to draw a point in the screen. Such instructions then can be used by other programmers.
Nowadays, many computers pretend to execute several programs at the same time. That is usually well-known as multi-task. In fact, CPU executes the instructions of a program for a short period of time and, soon after, it changes for another program and it executes some of its instructions. This creates the illusion of several programs being executed simultaneously through the compartilhamento of the time of CPU among the programs. This compartilhamento of time and usually controlled by the operating system. Operating system A computer always needs of at least a program in execution for the whole time to operate. Typically this program is the operating system (or operative system). The operating system determines which program they will execute, when, and that resources (as memory and E/S) he can use. The operating system also supplies an abstraction layer on the hardware, and he/she gives access to the other programs supplying services, as programs managers of devices (drivers ") that allow to the programmers to write programs for different machines without the need of knowing especificidades of all the electronic devices of each one of them.