The cache memory is a very high speed and expensive memory, which is used to speed up the memory retrieval process.

A nibble is half a byte, which is usually a grouping A of 4 bits. Word is the number of bits a processor can bundle (read/write) at a time.

(i) Decimal Number system
(ii) Binary Number system
(iii) Octal Number system
(iv) Hexadecimal Number system

(1) It needs less space and looks slim.
(2) It consumes less power and does not radiate heat at the time of operation.

The types of monitors available such as CRT (Cathode Ray Tube), LCD (Liquid Crystal Display) and LED (Light Emitting Diodes).

Pictures on a monitor are formed with picture elements called PIXELS.

(i) Mouse
(ii) Light pen

IBM 1401, IBM 1620, UNIVAC 1108

ENIAC, EDVAC, UNIVAC 1

Since it is a positive number. 1's complement will come only for negative number.

(46)₁₀ into Binary = 101110₂

Memory enables the computer to store the program. The memory unit is of two types:
(i) Primary memory
(ii) Secondary memory
The primary memory is used to store data temporarily and secondary memory stores the data permanently.

The ALU is a part of CPU where various computing functions are performed on data. ALU performs arithmetic operations such as addition, subtraction, multiplication, division and logical operations.

Touch Screen:
A touch screen is a display device that allows the user to interact with a computer by using the finger. It can be quite useful as an alternative to a mouse or keyboard for navigating a Graphical User Interface (GUI). Touch screens are used on a wide variety of devices such as computers, laptops, monitors, smart phones, tablets, cash registers and information kiosks. Some touch screens use a grid of infrared beams to sense the presence of a finger instead of utilizing touch-sensitive input.

100₂ - 1₂

100₂ - 1₂ =011₂

(i) The octal number system is playing a vital role in digital computer work.
(ii) The octal number system has a base of 8: It means that it has eight unique symbols such as 0,1 ,2,3,4,5,6 and 7.
(iii) Thus, each digit of an octal number can have any value from 0 to 7

(i) The microprocessor which is an Integrated Circuit. Microprocessors were first introduced in early 1970s. The first general purpose microprocessor, 4004 was developed by Intel Inc.
(ii) The microprocessor is a programmable multipurpose silicon chip. It is driven by clock pulses. It accepts input as a binary data and after processing, it provides the output data as per the instructions stored in the memory.

(i) The ALU is a part of the CPU where various computing functions are performed on data.
(ii) The ALU performs arithmetic operations such as addition, subtraction, multiplication, division and logical operations.
(iii) The result of an operation is stored in internal memory of CPU.
(iv) The logical operations of ALU promote the decision-making ability of a computer.

(i) POST (Power-On Self-Test) is the diagnostic testing sequence that a computer's basic input! output system runs to determine if the computer keyboard, random access memory, disk drives and other hardware are working correctly.
(ii) If the necessary hardware is detected and found to be operating properly, the computer begins to boot.

CD	DVD
CD stands for Compact Disc	DVD stands for Digital Versatile Disc
Can store up to 700 MB	Capacity of DVD is 4.7 GB of data
CD's are single sided	DVD's are single or double sided
Due to capacity constraint, CD's cannot store movies of good quality	DVD's are used for storing movies with good quality
CD players cannot play DVD's	DVD players can play CD's

Depending upon the size of the data the microprocessor can be classified as
(a) 8 bit microprocessor
(b) 16 bit microprocessor
(c) 4 bit microprocessor
(d) 32 bit microprocessor
(e) 64 bit microprocessor.

Flash Memory Devices
Flash memory is an electronic (solid-state) non-volatile computer storage medium that can be electrically erased and reprogrammed. They are either EEPROM or EPROM. Examples for Flash memories are pendrives, memory cards etc. Flash memories can be used in personal computers, Personal Digital Assistants (PDA), digital audio players, digital cameras and mobile phones. Flash memory offers fast access times. The time taken to read or write a character in memory is called access time. The capacity of the flash memories vary from 1 Gigabytes (GB) to 2 Terabytes (TB).

BIu-Ray Disc
Blu-Ray Disc is a high-density optical disc similar to DVD. Blu-ray is the type of discussed for PlayStation games and for playing High-Definition (HD) movies. A double-layer Blu-Ray disc can store up to 50 GB (gigabytes) of data. This is more than 5 times the capacity of a DVD, and above 70 times of a CD. The format was developed to enable recording, rewriting and playback of high-definition video, as well as storing large amount of data. DVD uses a red laser to read and write data. But, Blu-ray uses a blue-violet laser to write. Hence, it is called as Blu-Ray.

A numbering system is a way of representing numbers. The most commonly used numbering system in real life is Decimal number system.· Other number systems are Binary, Octal, Hexadecimal number system. Each number system 'is uniquely identified by its base value or radix. Radix or base is the count of number of digits in each number system. Radix or base is the general idea behind positional numbering system.
Decimal Number System
It consists of 0,1,2,3,4,5,6,7,8,9(10 digits). It is the oldest and most popular number system used in our day to day life, In the positional number system, each decimal digit is weighted relative to its position in the number. This means that each digit in the number is multiplied by 10 raised to a power corresponding to that digit's position.

Binary Number System
There are only two digits in the Binary system, namely, 0 and 1. The numbers in the binary system are represented to the base 2 and the positional multipliers are the powers of2. The left most bit in the binary number is called as the Most Significant Bit (MSB) and it has the largest positional weight. The right most bit is the Least Significant Bit (LSB) and has the smallest positional weight.

Octal Number System
Octal number system uses digits 0,1,2,3,4,5,6 and 7-(8 digits). Each octal digit.has its own positional value or weight as a power of 8.
Example
The Octal sequence (547)₈ has the decimal equivalent:

Hexadecimal Number System:
A hexadecimal number is represented using base 16. Hexadecimal or Hex numbers are used as a shorthand form of binary sequence. This system is used to represent data in a more compact manner. Since 16 symbols are used, 0 to F, the notation is called hexadecimal. The first 10 symbols are the same as in the decimal system, 0 to 9 and the remaining 6 symbols are taken from the first 6 letters of the alphabet sequence, A to F, where A represents 10, B is 11, C is 12, D is 13, E is 14 and F is 15.

S.No	Type of Mouse	Mechanism	Developed and Introduced
1		1. A small ball is kept inside and touches the pad through a hole at the bottom of the mouse. 2. When the mouse is moved, the ball rolls. 3.This movement of the ball is converted into signals and sent to the computer.	Telefunken, German Company, 0211011968
2		1. Measures the motion and acceleration of pointer. 2. It uses light source instead of ball to judge the motion of the pointer. 3. Optical mouse has three buttons. 4. Optical mouse is less sensitive towards surface.	In 1988, Richard Lyon, Steve Krish independently invented different versions of Optical Mouse.
3		1. Measures the motion and acceleration of pointer. 2. Laser Mouse uses Laser Light. 3. Laser Mouse is highly sensitive and able to work on any hard surface.

1101010₂ + 101101₂
1101010
+101101
________
10010111
________
1101010₂ + 101101₂  = 10010111₂

(a) Inkjet Printer:
(i) Inkjet printer use colour cartridges which combined magenta, yellow and cyan inks to create colour tones.
(ii) A black cartridge is used for monochrome output. Inkjet printer works by spraying ionised ink at a sheet of paper.
(iii) The speed of inkjet printers generally range from 1-20 ppm (page per minute)
(iv) An inkjet printer can spread millions of dots of ink at the paper every single second.
(v) They use the technology of firing ink by heating it so that it explodes towards the paper in bubbles or by using piezo electricity in which tiny electric currents are controlled by electronic circuits.
(b) Multimedia Projector:
(i) Multimedia projectors are used to produce computer output on a big screen.
(ii) These are used to display presentations in meeting halls or in class rooms.
(c) Barcode/ QR code Reader:
(i) A Bar code is a pattern printed in lines of different thickness.
(ii) The Bar code reader scans the information on the bar codes transmits to the computer for further processing.
(iii) The system gives fast and error free entry of information into the computer.
Quick response (QR) code:
The QR code is the two dimension bar code which can be read by a camera and processed to interpret the image.

1. The Central Processing Unit(CPU) has a Memory Data Register (MDR) and a Memory Address Register (MAR).
2. The Memory Data Register (MDR) keeps the data which is transferred between the Memory and the CPU. The Program Counter (PC) is a special register in the CPU which always keeps the address of the next instruction to be executed.
3. The Arithmetic and Logic unit of CPU places the address of the memory to be fetched, into the Memory Address Register.
4. A bus is a collection of wires used for communication between the internal components of a computer.
5. The address bus is used to point a memory location. A decoder, a digital circuit is used to point to the specific memory location where the word can be located.
6. The address register is connected with the address bus, which provides the address of the instruction. A data bus is used to transfer data between the memory and the CPU.
7. The data bus is bidirectional and the address bus is unidirectional. The control bus controls both read and write operations.
8. The read operation fetches data from memory and transfers to MDR. A single control line performs two operations like Read/Write using 1 or 0.
9. Also, the write operation transfers data from the MDR to memory. This organisation is shown below.

10. The word in the RAM has the same size (no.of bits) as the Memory Data Register (MDR). If the processor is an 8-bit RAM processor like Intel 8085, its MDR and the word in the both have 8 bits.
11. If the size of the MDR is eight bits, which can be connected with a word in the memory which is also eight bits size. The data bus has eight parallel wires to transfer data either from MDR to word or word to MDR based on the control(Read or write).

13. This control line is labeled as which becomes 1 means READ operation and 0 means WRITE operation. 

14. These pictures show the contents of MDR and the word before and after the READ operation.
i. The read operation transfers the data(bits) from word to Memory Data Register.
ii. The write operation transfers the data(bits) from Memory Data Register to word.