1.2 memory Isaac Clements

1.2 memory Isaac Clements

1. virtual memory

   • Virtual memory is a memory management capability of an OS that uses hardware and software to allow a computer to compensate for physical memory shortages by temporarily transferring data from random access memory (RAM) to disk storage. Virtual address space is increased using active memory in RAM and inactive memory in hard disk drives (HDDs) to form contiguous addresses that hold both the application and its data.

2. Cache

   • a collection of items of the same type stored in a hidden or inaccessible place.
     • A type of memory that is used in high-performance systems, inserted between the processor and memory proper. The memory hierarchy on a system contains registers in the processor, which are the highest-speed storage, and, at a slightly lower level of accessibility, the contents of the main memory.

3. Solid State

   • A solid-state drive (SSD), also incorrectly known as solid-state disk is a solid-state storage device that uses integrated circuit assemblies as memory to store data persistently. ... SSDs have no moving mechanical components.
     • Solid state is a term that refers to electronic circuitry that is built entirely out of semiconductors. The term was originally used to define those electronics such as a transistor radio that used semiconductors rather than vacuum tubes in its construction. Most all electronics that we have today are built around semiconductors and chips.

4. Flash

   • Flash memory, also known as flash storage, is a type of nonvolatile memory that erases data in units called blocks. A block stored on a flash memory chip must be erased before data can be written or programmed to the microchip. Flash memory retains data for an extended period of time, regardless of whether a flash-equipped device is powered on or off.

5. Registers

   • A processor register (CPU register) is one of a small set of data holding places that are part of the computer processor. A register may hold an instruction, a storage address, or any kind of data (such as a bit sequence or individual characters). Some instructions specify registers as part of the instruction. For example, an instruction may specify that the contents of two defined registers be added together and then placed in a specified register.

6. Non volatile (Doesn't delete when the Computer is turned on)

   • ROM
     • ROM is memory that cannot be changed by a program or user. ROM retains its memory even after the computer is turned off. For example, ROM stores the instructions for the computer to start up when it is turned on again.
       • Read Only Memory (ROM) is a special type of non volatile memory that is used for certain functions, e.g. to store the computer system's Basic Input/Output System and also to store instructions that are required to be carried out when the computer is first switched on, e.g. Power On Self Test (POST).

7. Volatile memory (it deletes when the computer is turned off)

   • RAM
     • Currently RAM is measured in megabytes and gigabytes. A typical computer system will have from 256MB to 4MB installed. The general rule of thumb is that the more memory you have installed the faster the system will be.

8. A computer uses two types of storage. A main store consisting of ROM and RAM, and backing stores which can be internal, eg hard disk, or external, eg a CD or USB flash drive.

9. When power is turned on, POST (Power-On Self-Test) is the diagnostic testing sequence that a computer's basic input/output system (or "starting program") runs to determine if the computer keyboard, random access memory, disk drives, and other hardware are working correctly.