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Class 6 Subject: Science Title of the Book: IT Planet Petabyte Chapter 2:

GENERAL INSTRUCTIONS:

• Exercises to be written in the book. • Assignment questions to be done in ruled sheets. • You Tube link is for the explanation of Primary and Secondary Memory.

YouTube Link:

➢ https://youtu.be/aOgvgHiazQA

INTRODUCTION:

➢ Computer can store a large amount of safely in their memory for future use. ➢ A computer’s memory is measured either in or . ➢ The memory of a computer is divided into two categories: Primary Memory, Secondary Memory. ➢ There are two types of Primary Memory: ROM and RAM. ➢ Memory is used to store program and instructions that are frequently used.

EXPLANATION:

Computer Memory: Memory plays a very important role in a computer. It is the basic unit where data and instructions are stored temporarily. Memory usually consists of one or more chips on the mother board, or you can say it consists of electronic components that store instructions waiting to be executed by the , data needed by those instructions, and the results of processing the data.

Memory Units: Computer memory is measured in bits and bytes. A is the smallest unit of information that a computer can process and store. A group of 4 bits is known as nibble, and a group of 8 bits is called . A byte is the minimum space required to store a character.

The computer memory is divided into two types – Primary Memory and Secondary Memory.

Primary Memory: is known as the working memory or the main memory of a computer system. Primary memory is of two types- volatile and nonvolatile. When the computer power is turned off, loses its contents. Non Volatile memory (NVM) does not lose its contents when the computer is turned off. RAM and ROM are two major types of primary memory. They are made up of material. A computer cannot run without primary memory.

RAM (Random Access Memory): also called main memory, consists of memory chips that can be read from and written to by the processor and other devices. RAM is a volatile memory. It loses its contents when the computer is turned off.

Types of RAM: DRAM, SRAM, MRAM

Dynamic RAM (DRAM) is inexpensive and the most popular type of main memory used in . Many variants of DRAM chips exist most of which are faster than the basic DRAM.

• SDRAM (Synchronous DRAM) – It is faster and more reliable than DRAM. • DDR SDRAM ( SDRAM) – It is faster than SDRAM and transfer data twice, instead of once for each clock cycle. • DDR2 – It is the second generation of DDR with faster speed. • DDR3 – It is the third generation of DDR which is designed for computers with multicore processors. It is faster than DDR2. • DDR4 – It is the fourth generation of DDR which is faster than DDR3. • RDRAM ( DRAM) – It is much faster than SDRAM.

Static RAM (SRAM) is efficient and fast but is very expensive. SRAM is used in small amounts as cache memory in a computer.

Magneto-resistive RAM (MRAM) is a newer type of RAM which stores data using magnet charges instead of electrical charges. MRAM retains its contents after the computer is switched off, which could prevent loss of data for users. : is a circuit board that holds memory chips. RAM is a type of memory chip that makes up the main memory in the computer systems. Two types of memory modules are (Single In-line Memory Module) and (Dual In-line Memory Module).

RAM requirements: The amount of RAM on the computer determines the amount of programs and data a computer can at one time, which affects the overall performance. A computer can only manipulate data that is in its main memory. More the RAM, faster the computer will respond.

ROM (Read Only Memory): refers to memory chips used for storing data that can be read only. The data on ROM chips cannot be modified, hence, the name read only memory. ROM is non-volatile. Its contents are not lost when the computer is switched off. The ROM chips are also called firmware. Some of the variations of the ROM chips are:

• A Programable Read Only Memory (PROM) chip is a blank ROM chip on which you can place items permanently. Programmers use microcode instructions to program a PROM chip. • An Erasable Programable ROM (EPROM) is another type of ROM the contents of which are erased by ultraviolet light and then reprogramed by a PROM program. • An Electrically EPROM(EEPROM) is another variation of the PROM chip which allows a programmer to erase the micro code with an electric signal.

Cache Memory is a temporary storage area for instructions and data that enhances the CPU speed. Most of today’s computers improve their processing time with cache memory. Most modern computers have three layers of cache memory: Level 1, Level 2, Level 3.

Secondary Memory is used to store data for a long time. This memory is permanent in nature. So, it is known as Non-volatile Memory. It is also known as back-up memory. The main example of secondary memory is Hard-Disk.

ASSIGNMENT QUESTIONS (To be done on ruled sheets)

Q1. Write difference between Primary and Secondary memory.

Q2. Write the full forms of the following:

a) ROM

b) RAM

) EPROM

d) PROM

Q3. What is the difference between Nibble and Byte?

Q4. Name 2 types of Primary memory.

Q5. Explain the term Byte.