A computer is an electronic machine designed to take input, process it, and display output as pre-defined instructions.

Hardware i.e., the physical components and software are the programming. The computer operates on IPO (Input, Processing, Output).

• Input: Data is fed in the computer via input devices such as a mouse or keyboard.

• Processing: The data is processed by CPU (Central Processing Unit) according to instructions.

• Output: The processed information (data) is delivered via output devices like a monitor and printer.

• A computer can store data using primary memory (RAM) for temporary use or secondary memory for long storage.

• RAM refers to Random Access Memory.

• ROM refers to Read Only Memory. It cannot change files in the computer; it only stores instructions that can be read, not written, by a user.

Characteristics of computer:

1. Speed – A computer can process billions of instructions per second. Modern processors have speed measured in GHz, meaning they can handle billions of cycles per second.
2. Accuracy – Computers follow instructions and produce all results without errors, except for bugs or human error.
3. Automation – Once programmed, a computer operates automatically.
4. Storage – Computers store vast amounts of data in primary memory.
5. Versatility – A simple computer can perform many tasks such as playing a movie or editing a document.
6. Diligence – A computer can perform repetitive tasks without pause.
7. Cost-effectiveness – The automation and speed of computers reduce the time and manpower required to complete tasks.

Block Diagram of a Computer

It lists its main components and their interactions.

• Input Unit – Devices like the keyboard, mouse, and scanner convert user data and instructions into a format that the computer can understand.
  • CPU – The brain of the computer, responsible for processing all instructions.
  • ALU (Arithmetic Logic Unit) – Performs arithmetic and logical operations, e.g., +, −, ×, <, >, =.
  • CU (Control Unit) – Directs the flow of data between input, memory, and output units.
  • Memory Unit – Stores data and instructions.
  • Output Unit – Converts processed data into a human-readable form.

Fig. 1: Block diagram of a computer

Different between h/s.
All are five Generations;
The Computer Generations can be classified into five categories:

1. First Generation
2. Second Generation
3. Third Generation
4. Fourth Generation
5. Fifth Generation

The first generation used vacuum tubes as the main electronic response for processing data.

• The first generations were from 1942–1955.
• These computers were physically large and required huge rooms.
• Used magnetic drums for memory storage.
• Used punched cards and paper tapes for input/output.
  Disadvantages:
• They consumed more power.
• These computers were large in size.
• These computers produced a large amount of heat.
• They had limited commercial use.

The second generation computers were manufactured in the years 1955–1964.

• These computers used transistors in place of vacuum tubes.
• They were smaller in size and required less space for installation.
• They used magnetic tapes as secondary storage devices.
• They consumed less power and produced less amount of heat.
• They were about 10 times faster than first generation computers.
• They were more reliable.
• Less prone to hardware failure compared to the first generation.

The third generation computers were manufactured in the years 1964–1975.

• These computers used integrated circuits (ICs) instead of vacuum tubes and transistors.
• The size of these computers was smaller than earlier computers.
• These computers used magnetic disks as their secondary storage devices.
• Development of standard programming languages such as FORTRAN and BASIC.
• The manufacturing cost of these computers was less compared to previous generations.
• These computers used standard I/O devices such as keyboard, mouse, and monitors.
• These systems were used for both scientific and commercial purposes.
• They were more reliable and less prone to errors.

The fourth generation of computers were manufactured in the years 1975–1989.

• These systems used microprocessors as the main electronic processing devices.
• The size of these computers was very small compared to previous generations.
• They consumed less power than third generation computers.
• They used large primary and secondary storage compared to third generation.
• These computers used standard high-level languages such as C, C++, JAVA, and Data Structures.
• These systems could use GUI (Graphical User Interface).
• They were more reliable and less prone to hardware failures than third generation.
• These computers could be networked (e.g., Printing).

The fifth generation computers were manufactured in the year 1989 onwards.

• Fifth generation computers used Artificial Intelligence (AI) instead of ICs and transistors.
• AI is a branch of Computer Science that aims to make computers behave like humans.
• These computers are portable and much smaller than fourth generation computers.
• Fifth generation computers are faster than fourth generation.
• They consume less power compared to fourth generation.
• These computers are user-friendly and support multimedia.
• The goal of fifth generation devices is to respond to human languages such as English and Hindi.

Number Systems

1. Binary – Bi 2 uses 0 & 1 – Base/Radix is 2 e.g. (11011)₂
2. Octal system Oct 8 digits from 0 to 7 Base/Radix is 8 – e.g. (11011)₈
3. Decimal Dec 10 digits from 0 to 9 – Base/Radix is 10 – e.g. (101101)₁₀
4. Hexadecimal – Hexa – 16 – digits 0 to 15 or A to F – Base/Radix is 16 – e.g. (1011011)₁₆

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15] → A B C D E F

Converting Binary System to Octal System & Decimal System to Binary System.

Examples:

• (56)(_{10})
• (614.62)(_8)
• (327.728)(_{10})

Conversion Table

Convert into Binary System	Octal Table
0	0 0 0	0	0	0
1	0 0 1	0	0	1
2	0 1 0	0	1	0
3	0 1 1	0	1	1
4	1 0 0	1	0	0
5	1 0 1	1	0	1
6	1 1 0	1	1	0
7	1 1 1	1	1	1

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