Memory Organization
1 Memory Basics
Memory is the workspace for the computers processor. It is a temporary storage area where the programs and data being operated on by the processor must reside. Memory storage is considered temporary because the data and programs will remain there only as long as the computer has electrical power or is not reset. Before being shut down or reset, any data that has been changed should be saved to a more permanent storage device of some type (usually a hard disk) so it can be reloaded into memory again in the future. We often call memory RAM, for Random Access Memory. Main memory is called RAM because you can randomly (and quickly) access any location in memory. When we talk about a computers memory, we usually mean the RAM in the system, meaning primarily the memory chips or modules that make up the primary active program and data storage used by the processor. This is often confused with the term storage, which should be used when referring to things such as disk and tape drives (although some people do consider them a form of memory).
2 Types of Memory
To better understand physical memory in a system, it is necessary to see where and how it fits into the system. Three main types of physical memory used in modern PCs are
• ROM: Read Only Memory
• DRAM: Dynamic Random Access Memory
• SRAM: Static RAM
2.1 ROM
Read Only Memory, or ROM, is a type of memory that can permanently or semipermanently hold data. It is called read-only because it is either impossible or difficult to write to. ROM is also often referred to as non-volatile memory because any data stored in ROM will remain, even if the power is turned off.
As such, ROM is an ideal place to put the PCs startup instructionsthat is, the software that boots the system. Note that ROM and RAM are not opposites, as some people seem to believe. In fact, ROM is technically a subset of the systems
RAM. In other words, a portion of the systems Random
Memory is the workspace for the computers processor. It is a temporary storage area where the programs and data being operated on by the processor must reside. Memory storage is considered temporary because the data and programs will remain there only as long as the computer has electrical power or is not reset. Before being shut down or reset, any data that has been changed should be saved to a more permanent storage device of some type (usually a hard disk) so it can be reloaded into memory again in the future. We often call memory RAM, for Random Access Memory. Main memory is called RAM because you can randomly (and quickly) access any location in memory. When we talk about a computers memory, we usually mean the RAM in the system, meaning primarily the memory chips or modules that make up the primary active program and data storage used by the processor. This is often confused with the term storage, which should be used when referring to things such as disk and tape drives (although some people do consider them a form of memory).
2 Types of Memory
To better understand physical memory in a system, it is necessary to see where and how it fits into the system. Three main types of physical memory used in modern PCs are
• ROM: Read Only Memory
• DRAM: Dynamic Random Access Memory
• SRAM: Static RAM
2.1 ROM
Read Only Memory, or ROM, is a type of memory that can permanently or semipermanently hold data. It is called read-only because it is either impossible or difficult to write to. ROM is also often referred to as non-volatile memory because any data stored in ROM will remain, even if the power is turned off.
As such, ROM is an ideal place to put the PCs startup instructionsthat is, the software that boots the system. Note that ROM and RAM are not opposites, as some people seem to believe. In fact, ROM is technically a subset of the systems
RAM. In other words, a portion of the systems Random