SECTION III-2: Internal Organization of Computers

The internal working of every computer can be broken down into three parts:

  • CPU (Central Processing Unit)
  • Menory
  • I/O (Input / Output) devices


Inside the Computer


The function is the CPU is to execute and process information stores in memory. The function of the I/O devices such as the keyboard and video monitor is to provide a means of communicating with the CPU. the CPU is connected to memory and I/O through strips of wire called a bus. The bus inside a computer carries information from place to place just as a street bus carried people from place to place. In every computer, there are three types of buses:

  1. Address Bus
  2. Data Bus
  3. Control Bus


For a device, memory or I/O to be recognized by the CPU, it must be assigned an address. The address assigned to a given device must be unique; no two devices are allowed to have the same address. The CPU puts the address in binary, on the address bus, and the decoding circuitry finds the device. Then the CPU uses the data bus either to get data from that device or to send data to it. The control buses are used to provide read or write signals to the device to indicate if the CPU is asking for information or sending information. Of the three buses, the address bus and data bus determine the capability of a given CPU.



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