Anatomy of a Digital Computer

Computer Science >> Anatomy of a Digital Computer

There are two main characteristics of a computer: (i) It responds to a particular set of instructions in a well-defined format. (ii) It may execute a pre-recorded list of instructions or a program. Modern computers are electronic or digital. The actual machinery such as transistors, wires and circuits is known as hardware and the instructions or data are known as software.

The major components of a computer are:

CPU (Central Processing Unit): The CPU has two parts that is Control Unit (CU) or Arithmetic Logic Unit (ALU). CPU is also known as the brain of a computer as it executes the program instructions.

Control unit (CU): The control unit of computer is tells that how the rest of the computer system carries out a program’s instructions. CU is directs to the movement of electronic signals between memory –that is temporarily holds instructions, data or processes information - and the ALU. ALU is also directs with these control signals between the CPU and the input/output devices.

ALU (Arithmetic Logic Unit): ALU does two kinds of operations - arithmetical and logical. Arithmetical operations of ALU are the fundamental mathematical operations. These operations consist addition, subtraction, multiplication or division. Logical operations of ALU consist of comparisons. Logical type operation is two pieces of data these are use to compare to see whether one is equal to, less than or greater than the other one.

Memory: Computer memory is the working storage part or area in the computer. There are two types of computer memory: primary memory and secondary memory.

Primary memory: Primary memory is working directly by the processing unit. The examples of primary memory are RAM, ROM. The data of the primary memory are lost as we switched off the computer. Primary memory is expensive than the secondary memory.

Secondary Memory: Secondary memory is magnetic disk, floppy disk etc. These memories are located outside the computer. The additional memory is that is secondary memory is required in all the computer systems to store the hundreds of millions of bytes of the data for the CPU to process. This memory is also known as auxiliary memory or secondary storage.

Input device: Input devices convert input data and instructions into the binary form for understand by the computer. There are different types of input devices like keyboard, Magnetic Ink Character Recognition (MICR), Optical Character Recognition (OCR), mark sense reader, etc.

Output device: Output devices are that type of devices that receive information from the CPU and present this information to the user in the desired form. Output devices include display screen, printers, loudspeakers, plotters, etc.

Secondary storage: Secondary storage are such as floppy disk, magnetic disk, etc., this is located outside the computer. The additional memory is also required in all the computer systems to store the hundreds of millions of bytes of data for the CPU to process. This memory is known as auxiliary memory or secondary storage. This type of memory the cost per bit of storage is low. That is why; the operating speed is slower than the primary memory. Big volume of data is stored on this type of memory on permanent basis and can transfer to the primary storage as it is and when required. Mostly used secondary storage devices are magnetic disks, magnetic tapes or floppy disks.

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