⭐⭐ What is memory:-
Computer data storage, often called storage or memory, refers to computer components, devices, and recording media that retain digital data used for computing, for some interval of time. Computer data storage provides one of the core function of the modern computer, that of information retention. it is one of the fundamental components of all modern, computers, and coupled with a central processing unit (CPU, a processor), implements the basic computer model used since the 1940s.
Computer is an electronic machine is it knows only "ON" or "OFF" i.e., "0" or "1". All the data in computer, processor or stored is converted into combination of 0s and 1s. This is called binary notation and 0 or 1 are called bits.
⭐ Bit is a basic memory unit.
⭐ 1Byte is unit of data that consist of 8 bits
⭐ 1 Kilo Byte ( KB) equal 1024 Bytes
⭐ 1 Mega Byte( MB) equal 1024 Kilo Bytes
⭐ 1 Giga byte (GB) equal 1024 Mega Bytes
⭐ 1 Tera Bytes ( TB) equal 1024 Giga Bytes
⭐ 1 Peta bytes (PB) equal 1024 tera bytes
⭐ 1 Exa byte (EB) equal to 1024 peta bytes
⭐ 1 Zetta byte (ZB) equal to 1024 Exa bytes
⭐ 1 Yotta Byte (YB) equal to 1024 Zetta bytes
⭐ 1 Bronto Byte ( BB) equal to 1024 Yotta bytes
⭐ 1 Geop Byte equal to 1024 Bronto bytes.
👉 Types of Memory:-
Our next step is to focus on memory. Here we will consider the types of memory on the basic of storage type and capability.
👉 Primary memory:- Primary storage, presently known as memory, is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated is also stored there in uniform manner.
Two memories are comprised in primary memory:
👉RAM(Random Access Memory):- RAM is a form of computer data storage. Today it take the form of integrated circuits that allows the stored data to be accessed in any order (i.e. at random). The word random thus refers to the fact that any piece of data can be retuned in a constant time, regardless of its physical location and whether or not it is related to previous piece of data. The word RAM is mostly associated with volatile types of memory (Such as DRAM memory modules), where the information is lost after the power is switched off. However, many other types of memory are RAM as well (i.e., Random Access Memory), including most types of ROM and a kind of flash memory called NOR-Flash.
👉ROM(Read-only-memory):- ROM is a class of storage media used in computers and other electronic devices. Because data stored in ROM cannot be modified (at least not very quickly or easily), it is mainly used to distribute firmware (software that is very closely tied to specific hardware, and unlikely to require frequent updates).
In its strictest sense, ROM refers only to mask ROM (the oldest type of solid state ROM), which is fabricated with the desired data permanently stored in it, and thus can never be modified. However, more modern types such as EPROM and flash EEPROM can be erased and re-programmed multiple times; they are still described as "read-only memory (ROM) because the reprogramming process is generally infrequent, comparatively slow, and often does not permit random access writes to individual memory location. Despite the simplicity of mask ROM, economies of scale and field-programmability often make reprogrammable technologies more flexible and inexpensive, so mask ROM is rarely used in new products as of 2007.
👉 Secondary Memory :- Secondary storage, or storage in popular usage, differs from primary storage in that it is not directly accessible by the CPU. The computer usually uses its input/ output channels to access secondary storage and transfers the desired data using intermediate area in primary storage. Secondary storage does not lose the data when the device is powered down-it is non-volatile. Per unit, it is typically also an order of magnitude less expensive than primary storage. Consequently modern computer system typically have an order of magnitude more secondary storage than primary storage and data is kept for longer time there.
In modern computers, hard disks are usually used as secondary storage. The time taken to access a given bytes of information stored on a hard disk is typically a few thousandths of a second, or milliseconds. By contrast, the time taken to access a given bytes of information storage in random access memory is measured in billionths of a second, or nanoseconds. This illustrates the very significant access-time difference which distinguishes solid-state memory from rotating magnetic storage devices: hard disk are typically about a million times slower than memory. Rotating optical storage devices, such as CD and DVD drives, have even longer access times.
👉 Tertiary Storage:- Tertiary Storage or tertiary memory provides a third level of storage. Typically it involves a robotic mechanism which will mount (insert) and dismount removable mass storage media into a storage device according to the system's demands; this data is often copied to secondary storage before use. It is primary used for archival of rarely accessed information since it is much slower than secondary storage ( e.g., 5-60 seconds vs. 1-10 milliseconds). This is primarily useful for extraordinarily large data. storage accessed without human operators. Typical examples include tape libraries and optical jukeboxes.
When a computer needs to read information from the tertiary storage, it will first consult a catalog database to determine which tape or disc contains the information. Next, the computer will instruction a robotic arm fetch the medium and place it in a drive. When the computer has finished reading the information, the robotic arm will return the medium to its place in the library.
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