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                     It's an electronic machine which can receive informations and save them. Further it can treat these informations according to programs which have been recorded in the machine.

          These programs allow to classify, copy, erase, edit, display on the screen, present informations graphically or otherwise, send them to a printer, and do things like controlling another machine. As far as numerical informations are concerned these programs can accomplish a huge amount of calculations at light speed.

          Programs are series of instructions for the machine. The same way one can type a text to the keyboard and record it as text, one can also type a program of instructions and record it in such a way that the computer will recognize it as a program to carry out and not as a simple text.

          This could be compared with saying somebody "Stand up!". He will understand you are asking him to stand up and carry out that order if he wishes to. The machine not being aware by itself will simply carry out the instruction. But if one tells the person: "'Stand up!' - said the teacher", they will understand one is telling a story. The computer will simply record the story as text and will not try to carry out the instruction.

         All that makes us consider the following facts:

  • The informations can be stored either as data or as instructions to carry out.
  • A computer must have means to receive informations. (Input)
  • There must be ways to store information.
  • It must be able to treat the information, tell the type of information, is it a simple piece of data or an instruction to carry out? And in that case to carry it out at the programmed time. It must be able to convert it so that it is presented in the form that is appropriate to the situation, sort it and classify it. Perform calculations.
  • It has to have ways to relay the informations. (Output)

          The means to exchange informations with the computer (in or out) are through devices called peripherals, such as keyboard monitor or printer. One talks about peripherals because they are at the periphery of the central part of the computer. These are also called peripheral devices or simply devices. There are input devices and output devices.

          Storage of information is accomplished by devices called mass storage devices. These will be looked at in more details later. For now be aware that the most importants of them are hard disks. That's where are recorded all the texts and files you are creating when you are using your computer. Other mass storage devices are the floppy disk drive which is a device to handle floppy disks and the CR-ROM drive to handle CD-ROMs.

          The treating of informations as well as the execution of programs are accomplished by the central processing unit (CPU) which is really the key part of the computer. Also called processor or microprocessor. That's where all operations on bits are centralized. It's mode of operation is explained in a simplified way at the next page.


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Copyright 2003-2004 Jacques Lederer