TYPES OF MEMORY
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Primary memory (RAM and ROM) is the working memory of a computer that holds the data and instructions currently being processed. It is volatile and has limited capacity. Secondary memory (HDD, DVD, etc.) is used for permanent storage of large amounts of data and retains data even when powered off. RAM is faster than ROM but volatile, while ROM is non-volatile but slower and used for startup processes. Primary memory is accessed directly by the CPU while secondary memory requires data to be copied to primary memory first before CPU can access it.
TYPES OF MEMORY
- 1. Types of Memories Presented By :- Mrs. Surkhab Shelly
- 2. Memory unit is the amount of data that can be stored in the storage unit. This storage capacity is expressed in terms of Bytes.
- 4. 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.
- 5. Random Access Memory (RAM) – • It is also called as read write memory or the main memory or the primary memory. • The programs and data that the CPU requires during execution of a program are stored in this memory. • It is a volatile memory as the data loses when the power is turned off. • RAM is further classified into two types- SRAM (Static Random Access Memory) and DRAM (Dynamic Random Access Memory).
- 6. Read Only Memory (ROM) – ROM Stores crucial information essential to operate the system, like the program essential to boot the computer. It is not volatile. Always retains its data. Used in embedded systems or where the programming needs no change. Used in calculators and peripheral devices. ROM is further classified into 4 types- ROM, PROM, EPROM, and EEPROM. Types of Read Only Memory (ROM) – PROM (Programmable read-only memory) – It can be programmed by user. Once programmed, the data and instructions in it cannot be changed. EPROM (Erasable Programmable read only memory) – It can be reprogrammed. To erase data from it, expose it to ultra violet light. To reprogram it, erase all the previous data. EEPROM (Electrically erasable programmable read only memory) – The data can be erased by applying electric field, no need of ultra violet light. We can erase only portions of the chip.
- 7. Writing Data is Faster Temporary Storage Store Data in MBs Volatile Used in normal operations RAM Writing Data is Slower Permanent Storage Store Data in GBs Non Volatile Used for startup process of Computer. ROM
- 8. 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. CPU directly does not access these memories, instead they are accessed via input-output routines. The contents of secondary memories are first transferred to the main memory, and then the CPU can access it. 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
- 9. Parameter Primary memory Secondary memory Nature The primary memory is categorized as volatile & nonvolatile memories. The secondary memory is always a non-volatile memory. Alias These memories are also called internal memory. Secondary memory is known as a Backup memory or Additional memory or Auxiliary memory. Access Data is directly accessed by the processing unit. Data cannot be accessed directly by the processor. It is first copied from secondary memory to primary memory. Only then CPU can access it.
- 10. Formation It's a volatile memory meaning data cannot be retained in case of power failure. It's a non-volatile memory so that that data can be retained even after power failure. Storage It holds data or information that is currently being used by the processing unit. Capacity is usually in 16 to 32 GB It stores a substantial amount of data and information. Capacity is generally from 200GB to terabytes. Accesses Primary memory can be accessed by the data bus. Secondary memory is accessed by I/O channels. Expense Primary memory is costlier than secondary memory. Secondary memory is cheaper than primary memory.