Familiarization of PC Components

Concept of John Von Neuman:

            According to him, he classified the complicated pc devide into 5 different units,

  1. CPU.
  2. Input Unit.
  3. Output Unit.
  4. Working Storage Memory.
  5. Permanent Storage Memory.

central processing unit (CPU) is the portion of a computer system that carries out the instructions of a computer program, and is the primary element carrying out the computer’s functions. The central processing unit carries out each instruction of the program in sequence, to perform the basic arithmetical, logical, and input/output operations of the system.The main unit inside the computer is the CPU. This unit is responsible for all events inside the computer. It controls all internal and external devices, performs arithmetic and logic operations. The operations a microprocessor performs are called the instruction set of this processor. The instruction set is “hard wired” in the CPU and determines the machine language for the CPU. The more complicated the instruction set is, the slower the CPU works. Processors differ from one another by the instruction set. If the same program can run on two different computer brands they are said to be compatible. Programs written for IBM compatible computers will not run on Apple computers because these two architectures are not compatible..

A CPU is the central processing unit or “brain” of a computer. One of the most
important computer parts

The CPU is composed of several units…



The control unit directs and controls the activities of the internal and external devices. It interprets the instructions fetched into the computer, determines what data, if any, are needed, where it is stored, where to store the results of the operation, and sends the control signals to the devices involved in the execution of the instructions.


The arithmetic and logic unit (ALU) is the part where actual computations take place. It consists of circuits which perform arithmetic operations (e.g. addition, subtraction, multiplication, division) over data received from memory and capable to compare numbers.


While performing these operations the ALU takes data from the temporary storage area inside the CPU named registers. Registers are a group of cells used for memory addressing, data manipulation and processing. Some of the registers are general purpose and some are reserved for certain functions. It is a high-speed memory which holds only data for immediate processing and results of this processing. If these results are not needed for the next instruction, they are sent back to the main memory and registers are occupied by the new data used in the next instruction.


Time & Date of computer.    A clock is an instrument used to indicate, keep, and co-ordinate     time. Shorter than the natural units: the day ; the lunar month ; and the year . The clock rate is the rate in bits per second (measured in hertz) in any synchronous circuit, such as a central processing unit (CPU).


Input device is any peripheral (piece of computer hardware equipment) used to provide data and control signals to an information processing system (such as a computer). Input and output devices make up the hardware interface between computer as a scanner or 6DOF controller. Any hardware device that sends data to the computer, without any input devices, a computer would only be a display device and not allow users to interact with it,

Examples: Key Board, Mouse, Mic, Camera…etc


An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by an information processing system (such as a computer) to the outside world.In computing, input/output, or I/O, refers to the communication between an information processing system (such as a computer), and the outside world. Inputs are the signals or data sent to the system, and outputs are the signals or data sent by the system to the outside.

Examples of output devices: Speakers, Headphones, Screen (Monitor) and Printer


It’s the working environment of the CPU. It is also a Volatile memory, which means it loss memory while a power loss occurs. Hence it means Working storage is also a Temporary memory. CPU uses this memory as its primary storage place for the processing data, so that working storage is also known as Primary Memory.

Example for primary memory was RAM and ROM.


Hence the primary memory was temporary; we need to store data permanently. So In computer device, for the future purpose of data, we use Non-Volatile memory for storing. It is known as Permanent Memory. It is also known as Secondary Memory.

Example for Secondary memory is Hard Disk Drive, CD.. etc

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