A component in the computer used for strong instructions and data is called memory.
Memory Measuring Units
The data is digital computers is represented as a collection of bits. The smallest unit of data that can be used by a computer is called bit. A set of 8 bits is known as byte. One byte is required to store one character. The capacity of main memory is often measured in the number of bytes. Different units to measure are as follows:UNIT No. of bytes
1 Nibble = 4 bits
1 Byte = 8 bits1 Kilobyte (KB) = 1024 bytes = (2) power 10 bytes
1 Megabyte (MB) = 1024 KB = (2) power 20 bytes
1 Gigabyte (GB) = 1024 MB = (2) power 30 bytes
1 Terabyte = 1024 GB = (2) power 40 bytes
Types of Memory
Different types of memories are random access memory and read-only memory.
1. Random Access Memory (RAM)
2. Read-Only Memory (ROM)3. Cache Memory
4. CMOS
1.Random Access Memory (RAM)RAM stands for Random Access Memory. It is also called main memory or Direct Access Memory. Random access means that each individual byte in the entire memory is directly accessible. A program must be loaded into RAM before execution. Most desktop computers usually have 2GB or less memory. RAM is temporary memory. When the power is turned off, the information in this memory is lost. Thus it is called volatile memory. CPU can read data from RAM and write data to ROM. That is whey RAM is also known as read / write memory. It is used to store data and instruction while it is being executed.
Types of RAM
RAM is built by using two different techniques: a. Dynamic RAM
DRAM stands for Dynamic Access Memory. It is a type of memory that is used in most computers. It is the least expensive kind of RAM. It requires an electric current to maintain its electrical state. The electrical charge of DRAM decreases with time that may result is loss of data. DRAM is recharged or refreshed again to maintain data. The processor cannot access the data of DRAM when it is being refreshed. That is why it is show.b. Static RAM
SRAM stands for Static Random Access Memory. It can store its value without any need to refresh the data as long as the power is available. SRAM is more expensive. It does not need to be power-refreshed. CPU does not wait to access data so it is faster. It utilizes more power than DRAM. It is normally used to build a very fast cache memory.
2.Read-Only Memory (ROM)
SRAM stands for Static Random Access Memory. It can store its value without any need to refresh the data as long as the power is available. SRAM is more expensive. It does not need to be power-refreshed. CPU does not wait to access data so it is faster. It utilizes more power than DRAM. It is normally used to build a very fast cache memory.
2.Read-Only Memory (ROM)
Rom stands for Read Only Memory. The instructions in ROM prepare the computer for use. These contents of ROM can only be read but cannot be changed or deleted. It is not possible to write new information or instruction in ROM. It stored data and instructions permanently. When the power is switched off, the instructions stored in ROM are not lost. That is why ROM is known as non-volatile memory.The data and programs in ROM are stored by the manufacturer. ROM is used to store frequently used data and instructions. The instructions in ROM are automatically loaded into the memory of computer when the computer is switched on.Types of ROM
Different types of ROM are as follows:
1. PROM:
PROM stands for Programmable Read Only Memory. This form of ROM is blank. The user or manufacturer can write data and programs on it using special devices. The user can write data and instructions, the error cannot be removed from PROM. The chip becomes unusable.
2. EPROM:
EPROM stands for Programmable Read Only Memory. This from of ROM is initially blank. The user or manufacturer can write data and programs on it using special devices. The data and programs written on it can be erased using ultraviolet rays. The user then can write new program on it.
EPROM stands for Programmable Read Only Memory. This from of ROM is initially blank. The user or manufacturer can write data and programs on it using special devices. The data and programs written on it can be erased using ultraviolet rays. The user then can write new program on it.
3. EEPROM:
EEPROM stands for Electronically Erasable Programmable Read Only Memory.The user can erase and write instructions in EEPROM using electrical devices.The user can erase its contents electronically if any error occurs in writing instructions.The contents of EEPROM.
EEPROM stands for Electronically Erasable Programmable Read Only Memory.The user can erase and write instructions in EEPROM using electrical devices.The user can erase its contents electronically if any error occurs in writing instructions.The contents of EEPROM.
3.Cache Memory
Cache memory is designed to speed up the transfer of data and instructions. It is located inside or close to CPU. It is faster than RAM. The data and instructions .It is located inside or close to CPU. It is faster than RAM. The data and instructions that are most recently or most frequently used by CPU are stored in cache.The data and instructions are retrieved from RAM when CPU used them for first time. A copy of that data or instructions is stored in cache.The next time the CPU needs that data or instructions, it first looks in cache. If the required data is found there, it is retrieved from cache memory instead of main memory. It speeds up the working of CPU.4.CMOS
CMOS stands for complementary metal- oxide semiconductor.It stores configuration information of computer.The information includes the type of disk drivers, keyboard and monitor, current data & time and other start up information required during booting process. CMOS chip uses battery power toretain information even when the computer is turned off. The information in CMOS can be changed.