NCERT Solutions for Class 4 Computer Science Chapter 3 Hardware and Software

We have studied that computer is an electronic machine which can solve both arithmetical and logical problems according to the instructions given to it. It is a digital machine which completely depends upon the commands for its working. It understands machine language.
A computer is an electronic machine which accepts the data and instructions from the user as Input then processes the data according to the given instructions and finally gives out the desired result as Output. A computer completely depends on human-beings. It cannot do anything itself. It works according to the instructions given by the user.
Components of a Computer System. A computer system consists of Hardware and Software.

Hardware
All the physical parts of a computer are called hardware. They are further divided into many types depending on their function. These can be divided into Input device, Processing device, Output device and Storage device.
In addition there are other parts like wires, cables, switches, boxes etc. which also come under hardware.

Input Devices
To feed different kinds of data into the computer, we need input devices. These devices are Keyboard, Mouse, Joystick, Scanner, Microphone, Web Camera, OMR (Optical Mark Recognition), OCR (Optical Character Recognition), MICR (Magnetic Ink Character Recognition), MODEM (Modulator Demodulator) etc.

Processing unit is part of computer in which the data is processed. This is also known as the CPU (Central Processing Unit). The working of a human brain can be compared with the working of CPU. It can also be called the brain of the computer.
The CPU is further made up of three parts:

1. Arithmetic Logic Unit (ALU)
2. Control Unit (CU)
3. Memory Unit (MU)

1. Arithmetic Logic Unit (ALU): This unit performs all the arithmetic operations such as, multiplication, subtraction, addition and division. It also performs the logical operations which involve comparisons.
2. Control Unit (CU): CU controls all the operations of the computer system. It directs the inputs received from input devices to the memory unit and to the arithmetic logic unit. It also controls the flow of results or output from ALU to memory and to the output devices.
3. Memory Unit (MU): MU stores data and instructions before they are provided to the ALU for arithmetic and logical operations. It also stores the results given out by the ALU before they are passed onto the output devices.

These are those parts of a computer which are used to obtain the result from the computer. There are some commonly used output devices such as monitor, printer, plotter, speakers etc.
Storage Devices
Storage devices are used to store data and instructions in the computer. A computer has two types of storage:
1. Temporary storage
2. Permanent storage

1. Temporary Storage : It is also called RAM. RAM stands for Random Access Memory. All the data in this memory gets wiped off once the computer gets switched off without saving the data.
2. Permanent Storage : It is used to store data permanently so that it can be used again. Various devices are used as secondary storage devices. These devices are Floppy Disk, Compact Disk (CD), Pen Drive, Magnetic Tape, Zip Drive, Digital Video Disk (DVD), Hard Disk etc.

Software is very important component of a computer system. A computer needs instructions to perform any of the tasks. All the instructions which are given to a computer are in the form of programs. Now this program is a group of instructions which perform a specific task.

Software is a set of instructions that tells the computer how the work has to be done. Computer cannot work without a software. A computer being a machine knows nothing.
System software: Some software are used to control the internal working of the hardware devices. These software help the user to operate the computer. These are mainly called System software. For example, Windows is one of the examples of system software.

Application Software: Now other programs which are used to get specific applications or tasks are done by the computer is called Application software. Some of the examples of application software are Paint, Media Player, Power Point, Microsoft Word, MS Excel etc.