Computer generations are based on major technological changes in computers occurred, like the use of vacuum tubes, transistors, and the microprocessor. As of 2020, there are five generations of the computer.

Fig: Computer Fundamental Generation

First generation (1940 - 1956)

The first generation of computers used vacuum tubes as a major piece of technology. Vacuum tubes were widely used in computers from 1940 through 1956. Vacuum tubes were larger components and resulted in first generation computers being quite large in size, taking up a lot of space in a room. Some of the first generation computers took up an entire room.

Fig: First Generation Image

Second generation (1956 - 1963)

The second generation of computers saw the use of transistors instead of vacuum tubes. Transistors were widely used in computers from 1956 to 1963. Transistors were smaller than vacuum tubes and allowed computers to be smaller in size, faster in speed, and cheaper to build.

The first computer to use transistors was the TX-0 and was introduced in 1956. Other computers that used transistors include the IBM 7070, Philco Transac S-1000, and RCA 501.

Fig: Second Generation Image

Third generation (1964 - 1971)

The third generation of computers introduced the use of IC (integrated circuits) in computers. Using IC's in computers helped reduce the size of computers even more compared to second-generation computers, and make them faster.

Fig: Third Generation Image

Fourth generation (1972 - 2010)

The fourth generation of computers took advantage of the invention of the microprocessor, more commonly known as a CPU. Microprocessors, along with integrated circuits, helped make it possible for computers to fit easily on a desk and for the introduction of the laptop.

Some of the earliest computers to use a microprocessor include the Altair 8800, IBM 5100, and Micral. Today's computers still use a microprocessor, despite the fourth generation being considered to have ended in 2010.

Fig: Fourth Generation Image

Fifth generation (2010 to present)

The fifth generation of computers is beginning to use AI (artificial intelligence), an exciting technology that has many potential applications around the world. Leaps have been made in AI technology and computers, but there is still room for much improvement.

 

Fig: Fifth Generation Image

A memory is just like a human brain. It is used to store data and instructions. Computer memory is the storage space in the computer, where data is to be processed and instructions required for processing are stored.

Memory is primarily of three types −

• Cache Memory
• Primary Memory/Main Memory
• Secondary Memory

 

1.   Cache Memory

Cache memory is a very high speed semiconductor memory which can speed up the CPU. It acts as a buffer between the CPU and the main memory. The parts of data and programs are transferred from the disk to cache memory by the operating system, from where the CPU can access them.

 

Advantages

 

The advantages of cache memory are as follows −

• Cache memory is faster than main memory.
• It consumes less access time as compared to main memory.
• It stores the program that can be executed within a short period of time.
• It stores data for temporary use.

 

Disadvantages

 

The disadvantages of cache memory are as follows −

• Cache memory has limited capacity.
• It is very expensive.

Fig: Cache Memory

 

2.   Primary Memory (Main Memory)

 

Primary memory holds only those data and instructions on which the computer is currently working. It has a limited capacity and data is lost when power is switched off. It is generally made up of semiconductor device. These memories are not as fast as registers. The data and instruction required to be processed resides in the main memory. It is divided into two subcategories RAM and ROM.

 

Characteristics of Main Memory

• These are semiconductor memories.
• It is known as the main memory.
• Usually volatile memory.
• Data is lost in case power is switched off.
• It is the working memory of the computer.
• Faster than secondary memories.
• A computer cannot run without the primary memory.

 

3.   Secondary Memory

This type of memory is also known as external memory or non-volatile. It is slower than the main memory. These are used for storing data/information permanently.

 For example, disk, CD-ROM, DVD, etc.

Characteristics of Secondary Memory

• These are magnetic and optical memories.
• It is known as the backup memory.
• It is a non-volatile memory.
• Data is permanently stored even if power is switched off.
• It is used for storage of data in a computer.
• Computer may run without the secondary memory.
• Slower than primary memories.

 

Fig: Secondary Memory

Following are some of the important output devices used in a computer.

• Monitors
• Graphic Plotter
• Printer

 

1.   Monitors

 

Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the number of pixels.

There are two kinds of viewing screen used for monitors.

• Cathode-Ray Tube (CRT)
• Flat-Panel Display

 

1.   Cathode-Ray Tube (CRT) Monitor

 

The CRT display is made up of small picture elements called pixels. It takes more than one illuminated pixel to form a whole character, such as the letter ‘e’ in the word help.

Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically.

There are some disadvantages of CRT −

• Large in Size
• High power consumption

2.   Flat-Panel Display Monitor

 

The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the CRT. Current uses of flat-panel displays include calculators, video games, monitors, laptop computer, and graphics display.

 

  The flat-panel display is divided into two categories –

 

·        Emissive Displays 

 

Emissive displays are devices that convert electrical energy into light. For example, plasma panel and LED (Light-Emitting Diodes).

 

·        Non-Emissive Displays 

 

Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. For example, LCD (Liquid-Crystal Device).

 

Fig: Flat- Monitor

2.   Printers

 

Printer is an output device, which is used to print information on paper.

 

There are two types of printers −

• Impact Printers
• Non-Impact Printers

 

     I.            Impact Printers

Impact printers print the characters by striking them on the ribbon, which is then pressed on the paper.

 

Characteristics of Impact Printers are the following −

• Very low consumable costs
• Very noisy
• Useful for bulk printing due to low cost
• There is physical contact with the paper to produce an image

 

These printers are of two types −

• Character printers
• Line printers

 

Ø Character Printers

 

Character printers are the printers which print one character at a time.

These are further divided into two types:

• Dot Matrix Printer(DMP)
• Daisy Wheel

  

   Ø Dot Matrix Printer

 

Advantages

• Inexpensive
• Widely Used
• Other language characters can be printed

 

Disadvantages

• Slow Speed
• Poor Quality

 

Fig: Dot-Matrix Printer

  Ø Daisy Wheel

 

Advantages

• More reliable than DMP
• Better quality
• Fonts of character can be easily changed

 

Disadvantages

• Slower than DMP
• Noisy
• More expensive than DMP

 

Fig: Daisy-Wheel-Printer

 

Ø Line Printers

 

Line printers are the printers which print one line at a time.

 

These are of two types −

• Drum Printer
• Chain Printer

Fig: Line-Printer

 

  Ø Drum Printer

 

Advantages

• Very high speed

 

Disadvantages

• Very expensive
• Characters fonts cannot be changed

 

  

  Ø Chain Printer

 

Advantages

• Character fonts can easily be changed.
• Different languages can be used with the same printer.

 

Disadvantages

• Noisy

 

2.Non-impact Printers

 

Non-impact printers print the characters without using the ribbon. These printers print a complete page at a time, thus they are also called as Page Printers.

 

These printers are of two types −

• Laser Printers
• Inkjet Printers

 

Characteristics of Non-impact Printers

• Faster than impact printers
• They are not noisy
• High quality
• Supports many fonts and different character size

 

  Ø Laser Printers

 

These are non-impact page printers. They use laser lights to produce the dots needed to form the characters to be printed on a page.

 

Advantages

• Very high speed
• Very high quality output
• Good graphics quality
• Supports many fonts and different character size

 

Disadvantages

• Expensive
• Cannot be used to produce multiple copies of a document in a single printing

Fig: Laser Printer

 

Ø Inkjet Printers

 

Inkjet printers are non-impact character printers based on a relatively new technology. They print characters by spraying small drops of ink onto paper. Inkjet printers produce high quality output with presentable features.

 Color printing is also possible. Some models of Inkjet printers can produce multiple copies of printing also.

 

Advantages

• High quality printing
• More reliable

 

Disadvantages

• Expensive as the cost per page is high
• Slow as compared to laser printer

 

Fig: Inkjet Printer