Main Memory

MEMORY

Internal storage areas in the computer The term memory identifies data storage that comes in the form of chips, and the word storage is used for memory that exists on tapes or disks. Moreover, the term memory is usually used as a shorthand for physical memory, which refers to the actual chips capable of holding data. Some computers also use virtual memory, which expands physical memory onto a hard disk.
Every computer comes with a certain amount of physical memory, usually referred to as main memory or RAM. You can think of main memory as an array of boxes, each of which can hold a single byte of information. A computer that has 1 megabyte of memory, therefore, can hold about 1 million bytes (or characters) of information.

Memory Manufacturers Kingston, Rambus, Crucial, Samsung, PNY, Micron
Memory Terminology

Memory speed - measured in nanoseconds, this is the time to access data that is stored in memory
the lower the nanoseconds the faster the memory (2ns-80ns)

Parity - A simple error checking method use in memory correction

ECC-Error correction code use in memory correction for newer computers

Memory Banks - A socket where memory is installed Example 4 banks will have 8MB of memory each for a total of 32MB

There are several different types of memory:

240-pin DIMM----------------------------- DDR3 SDRAM

ROM or Read Only Memory, Computers almost always contain a small amount of read-only memory that holds instructions for starting up the computer. Unlike RAM, ROM cannot be written to. It is non-volatile which means once you turn off the computer the information is still there.


PROM, short for programmable read-only memory A PROM is a memory chip on which data can be written only once. Once a program has been written onto a PROM, it remains there forever. Unlike RAM, PROM's retain their contents when the computer is turned off. The difference between a PROM and a ROM (read-only memory) is that a PROM is manufactured as blank memory, whereas a ROM is programmed during the manufacturing process. To write data onto a PROM chip, you need a special device called a PROM programmer or PROM burner. The process of programming a PROM is sometimes called burning the PROM.

EPROM (erasable programmable read-only memory) is a special type of PROM that can be erased by exposing it to ultraviolet light. Once it is erased, it can be reprogrammed. An EEPROM is similar to a PROM, but requires only electricity to be erased.

EEPROM- Acronym for electrically erasable programmable read-only memory. Pronounced double-ee-prom or e-e-prom, an EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge. Like other types of PROM, EEPROM retains its contents even when the power is turned off. Also like other types of ROM, EEPROM is not as fast as RAM. EEPROM is similar to flash memory (sometimes called flash EEPROM). The principal difference is that EEPROM requires data to be written or erased one byte at a time whereas flash memory allows data to be written or erased in blocks. This makes flash memory faster.

RAM (Random Access Memory) is a temporary (Volatile) storage area utilized by the CPU. Before a program can be ran the program is loaded into the memory which allows the CPU direct access to the program.




2 Types of RAM

SRAM short for static random access memory and pronounced ess-ram. SRAM is a type of memory that is faster and more reliable than the more common DRAM (dynamic RAM). The term static is derived from the fact that it doesn't need to be refreshed like dynamic RAM.
SRAM is often used only as a memory cache usually found in the CPU (L1, L2 and L3 Cache)

DRAM stands for dynamic random access memory, a type of memory used in most personal computers.

Types of DRAM Packages and DRAM Memory

LAPTOP MEMORY
(72, 144, 200) SO-DIMM

SO-DIMM Short for Small Outline DIMM, a small version of a DIMM used commonly in notebook computers. 72 supports 32bit and 144 and 200 SO-DIMM pins supports a full 64-bit transfer.
(144, 172) Micro-DIMM

Micro-DIMM Short for Micro Dual Inline Memory Module, a competing memory used on laptops, mostly supports 144 and 172 pins.

SIMM Acronym for single in-line memory module, a small circuit board that can hold a group of memory chips. Typically, SIMM's holds up 8 (on Macintoshes) or 9 (on PCs) RAM chips. On PCs, the ninth chip is often used for parity error checking. Unlike memory chips, SIMM's is measured in bytes rather than bits. SIMM's is easier to install than individual memory chips. A SIMM is either 30 or 72 pins.
30 pin SIMM (Usually FPM or EDO RAM)

FPM RAM Short for Fast Page Mode RAM, a type of Dynamic RAM (DRAM) that allows faster access to data in the same row or page. Page-mode memory works by eliminating the need for a row address if data is located in the row previously accessed. It is sometimes called page mode memory.

72 pin SIMM (EDO RAM)

EDO DRAM Short for Extended Data Output Dynamic Random Access Memory, a type of DRAM that is faster than conventional DRAM. Unlike conventional DRAM which can only access one block of data at a time, EDO RAM can start fetching the next block of memory at the same time that it sends the previous block to the CPU.

DIMM Short for dual in-line memory module, a small circuit board that holds memory chips. A single in-line memory module (SIMM) has a 32-bit path to the memory chips whereas a DIMM has 64-bit path. Because the Pentium processor requires a 64-bit path to memory, you need to install SIMM's two at a time. With DIMM's, you can install memory one DIMM at a time. A DIMM contains 168 pins.

168 pin DIMM (SDRAM)
SDRAM Short for Synchronous DRAM, a new type of DRAM that can run at much higher clock speeds than conventional memory. SDRAM actually synchronizes itself with the CPU's bus and is capable of running at 133 MHz, about three times faster than conventional FPM RAM, and about twice as fast EDO DRAM . SDRAM is replacing EDO DRAM in many newer computers
SDRAM delivers data in high speed burst

184 pin DIMM (DDR-SDRAM)

DDR SDRAM Short for Double Data Rate-Synchronous DRAM, a type of SDRAM that supports data transfers on both edges of each clock cycle, effectively doubles the memory chip's data throughput. DDR-SDRAM is also called SDRAM II.

240 DIMM (DDR2-SDRAM)
DDR2-SDRAM Short for Double Data Rate Synchronous DRAM 2 is a type of DDR that supports
higher's speeds than it's predecessor DDR SDRAM

240 DIMM (DDR3-SDRAM)
DDR3-SDRAM Short for Double Data Rate Synchronous DRAM 3 is the newest type of DDR that supports the fastest speed of all the SDRAM memory

184 pin RIMM (RDRAM)

RIMM Rambus Inline Memory Module, The memory module used with RDRAM chips. It is similar to a DIMM package but uses different pin settings. Rambus trademarked the term RIMM as an entire word. It is the term used for a module using Rambus technology. It is sometimes incorrectly used as an acronym for Rambus Inline Memory Module. A RIMM contains 184 or 232pins. Note must use all sockets in RIMM installation or use C_RIMM to terminate banks

232 pin RIMM (RDRAM)
RDRAM Short for Rambus DRAM, a type of memory (DRAM) developed by Rambus, Inc.
In 1997, Intel announced that it would license the Rambus technology for use on its future motherboards, thus making it the likely de facto standard for memory architectures.
SIMM and DIMM Sockets


SDRAM Chart
168 DIMM (SDRAM)

Module Standard Module Format Chip Type Clock Speed
(MHz) Cycles Per clock Bus Speed Bus Width
(Bytes) Transfer Rate
(MB/s)
PC66 SDR DIMM 10ns 66 1 66 8 533
PC100 SDR DIMM 8ns 100 1 100 8 800
PC133 SDR DIMM 7ns 133 1 133 8 1,066

DDR SDRAM Chart
184 DIMM (DDR-SDRAM)

Module Standard Module Format Chip Type Clock Speed
(MHz) Cycles Per clock Bus Speed Bus Width
(Bytes) Transfer Rate
(MB/s)
PC1600 DDR DIMM DDR200 100 2 200 8 1,600
PC2100 DDR DIMM DDR266 133 2 266 8 2.133
PC2400 DDR DIMM DDR300 150 2 300 8 2,400
PC2700 DDR DIMM DDR333 166 2 333 8 2,667
PC3000 DDR DIMM DDR366 183 2 366 8 2,933
PC3200 DDR DIMM DDR400 200 2 400 8 3,200
PC3500 DDR DIMM DDR433 216 2 433 8 3,466
PC3700 DDR DIMM DDR466 233 2 466 8 3,733
PC4000 DDR DIMM DDR500 250 2 500 8 4,000
PC4300 DDR DIMM DDR533 266 2 533 8 4,266

DDR2 SDRAM Chart

240 DIMM (DDR2-SDRAM)
Module Standard Module Format Chip Type Clock Speed
(MHz) Cycles Per clock Bus Speed Bus Width
(Bytes) Transfer Rate
(MB/s)
PC2-3200 DDR2 DIMM DDR2-400 200 2 400 8 3,200
PC2-4300 DDR2 DIMM DDR2-533 266 2 533 8 4,266
PC2-5400 DDR2 DIMM DDR2-667 333 2 667 8 5,333
PC2-6400 DDR2 DIMM DDR2-800 400 2 800 8 6,400

240 DIMM (DDR3-SDRAM)

Module Standard Module Format Chip Type Clock Speed
(MHz) Cycles Per clock Bus Speed Bus Width
(Bytes) Transfer Rate
(MB/s)
PC3-6400 DDR3
DIMM DDR3-800 400 2 800 8 6,400
PC3-8500 DDR3
DIMM DDR3-1066 533 2 1,066 8 8,500
PC3-10600 DDR3
DIMM DDR3-1333 667 2 1,334 8 10,670
PC3-12800 DDR3
DIMM DDR3-1600 800 2 1,600 8 12,800

RDRAM Chart

232 RIMM (RDRAM)
Module Standard Module Format Chip Type Clock Speed
(MHz) Cycles Per clock Bus Speed Bus Width
(Bytes) Transfer Rate
(MB/s)
RIMM 1200 RIMM-16 PC600 300 2 600 2 1,200
RIMM 1400 RIMM-16 PC700 350 2 700 2 1,400
RIMM 1600 RIMM-16 PC800 400 2 800 2 1,600
RIMM 2100 RIMM-16 PC1066 533 2 1,066 2 2,133
RIMM 2400 RIMM-16 PC1200 600 2 1,200 2 2,400
RIMM 3200 RIMM-32 PC800 400 2 800 2 3,200
RIMM 4200 RIMM-32 PC1066 533 2 1,066 2 4,266
RIMM 4800 RIMM-32 PC1200 600 2 1,200 2 4,800
RAM Desktop Installation

Note RAM Memory Sticks come in the following sizes
8MB, 16MB, 32MB, 64MB, 128MB, 256MB, 512MB, 1GB, 2GB, 4GB and 8GB

SIMM – Single Inline Memory Module Installation (30 or 72 pin)

1. Place SIMM in a 45 degree angle, push it upright to lock with the corresponding notch on the sides
2. Must be installed in same pairs
3. Must populate first two slots of the SIMM sockets in order for it to work

DIMM – Dual Inline Memory Module Installation (168, 184 or 240 pin)
1. The first thing you do is open the plastic retaining clips on each side of slots you are going to use.
2. Align the cut-out on the module pin connector with the engaging pin on the slot
3. Holding the module upright press down both ends.
4. When the module is correctly seated, retaining clips should lock automatically.
5. DIMM’s can be installed as a single pair (unless it states Dual Channel then you must install it in pairs)

RIMM – Rambus Inline Memory Module Installation (184 or 232 pin)

1. The first thing you do is open the plastic retaining clips on each side of slots you are going to use.
2. Align the cut-out on the module pin connector with the engaging pin on the slot
3. Holding the module upright press down both ends.
4. When the module is correctly seated, retaining clips should lock automatically.
5. Must populate all RIMM slots available
3. If not unpopulated slots must use CRIMM’s (Continuity Rambus Inline Memory Module)

Memory Troubleshooting

MEMORY (when installing use a ground strap because of ESD)
ESD (low and high humidity)
Mixed Memory usually equals fried memory
Parity Errors or ECC Errors (Memory correction errors)
SIMMS must be installed in pairs
RIMMS must be all installed in all slots or CRIMM's must be needed in unvacated RIMM slots
General Protection Fault (memory overwrite)
Not enough memory (computer is slow)
NMI -Non Maskable Interrupt will cause BSOD (Blue Screen of Death)
Multiple beeps when booting up check that memory is properly installed and working
No Video (Reseat memory)
Memory speeds set in BIOS/CMOS Setup
Virtual Memory (Page fault)
Chip Creep - Thermal expansion and contraction

Introduction to Database

Database
A database is a structured collection of related data. A database helps us to keep the information in a organized way so that it can easily be accessed, managed, and updated.

Data – a collection of raw facts made up of text, numbers and dates.

Murray 35000 7/18/86

Information - the meaning given to data in a way so that it can be understood and interpreted.

Mr. Rohit is a sales person whose annual salary is 35, 0000 and whose hire date is July 18, 2009

Databases can be analyzed at different levels ,also known as Data Abstraction which means  hiding the complexities:

• View Level
• Logical /Conceptual Level
• Physical Level

View level: Application programs hide details of data types. Views can also hide information (e.g., salary) for security purposes.

Logical level: Describes what data is stored in database, and the relationships among the data

Physical level: Describes how a record (e.g., customer) is stored.

.

Type customer = record
Name: string;
Street: string;
City: integer;
End;

Data Models
A data model is a collection of tools for describing Data, Data relationships, Data semantics, and Data constraints.

Type of Data Model

1. Entity-Relationship Model
2. Relational Model
3. Other Models:
• Object-Oriented Model
• Older models: Network Model and Hierarchical Model

1. Entity-Relationship Model

• Entity: Entity is a Real-world object distinguishable from other objects.
• Relationship: Relationship is the association among two or more entities.

E-R model describes the real world Entities (objects) (E.g. customers, accounts, bank branch) and the Relationships between these entities. The entity-relationship model (or ER model) is a way of graphically representing the logical relationships between entities (or objects).


Components of E-R model:

• Rectangles representing entity sets.
• Ellipses representing attributes.
• Diamonds representing relationship sets.
• Lines links attributes to entity sets and entity sets to relationship sets.

Example of E-R Model:

2. Relational Model

The relational model used the basic concept of a relation or table. The columns or fields in the table identify the attributes such as name, age, and so. A tuple or row contains all the data of a single instance of the table. In the relational model, every tuple must have a unique identification or key based on the data.

Hierarchical Model

The Hierarchical Database Model defines hierarchically-arranged data. Relationships in such a system are thought of in terms of children and parents such that a child may only have one parent but a parent can have multiple children. Parents and children are tied together by links called "pointers" (perhaps physical addresses inside the file system). A parent will have a list of pointers to each of their children.


Network Model

The network model is very similar to the hierarchical model actually. In fact, the hierarchical model is a subset of the network model. However, instead of using a single-parent tree hierarchy, the network model uses set theory to provide a tree-like hierarchy with the exception that child tables were allowed to have more than one parent. This allowed the network model to support many-to-many relationships.

Computer Hardware

The hardware of computer is divided into three broad categories:

1. Processor/Processing Unit
2. Memory(Internal & External)
3. I/O (input/output).

Processor

The processor is the part of the computer that actually does the computations. This is sometimes called an MPU (Main Processor Unit) or CPU (Central Processing Unit or Central Processor Unit).
A processor typically contains an Arithmetic & Logic unit (ALU), Control Unit (CU).

Arithmetic & Logic Unit (ALU)

An arithmetic & logic unit (ALU) performs integer arithmetic and logic operations. It also performs shift and rotate operations and other specialized operations. Usually floating point arithmetic is performed by a dedicated Floating Point Unit (FPU), which may be implemented as a co-processor.

Control Unit (CU)

Control units are in charge of the computer. Control units fetch and decode machine instructions. Control units may also control some external devices.

Main Storage

Main storage is also called memory or internal memory (to distinguish from external memory, such as hard drives).

RAM is Random Access Memory, and is the basic kind of internal memory. RAM is called “random access” because the processor or computer can access any location in memory (as contrasted with sequential access devices, which must be accessed in order). RAM has been made from transistors, integrated circuits, magnetic core, or anything that can hold and store binary values (one/zero, plus/minus, open/close, positive/negative, high/low, etc.).

Static RAM is called static because it will continue to hold and store information even when power is removed. Magnetic cores are examples of static memory.
Dynamic RAM is called dynamic because it loses all data when power is removed. Transistors and integrated circuits are examples of dynamic memory.

ROM is Read Only Memory (it is also random access, but only for read). ROM is typically used to store things that will never change for the life of the computer, such as low level portions of an operating system.

Cache (pronounced cash) Memory :
Cache (pronounced cash) memory is extremely fast memory that is built into a computer’s central processing unit (CPU), or located next to it on a separate chip. The CPU uses cache memory to store instructions that are repeatedly required to run programs, improving overall system speed. The advantage of cache memory is that the CPU does not have to use the motherboard’s system bus for data transfer. Whenever data must be passed through the system bus, the data transfer speed slows to the motherboard’s capability. The CPU can process data much faster by avoiding the bottleneck created by the system bus.

Cache built into the CPU itself is referred to as Level 1 (L1) cache. Cache that resides on a separate chip next to the CPU is called Level 2 (L2) cache. Some CPUs have both L1 and L2 cache built-in and designate the separate cache chip as Level 3 (L3) cache.


Data storage device

Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data used for computing for some interval of time. Computer data storage provides one of the core functions of the modern computer, that of information retention. It is one of the fundamental components of all modern computers A data storage device is a device for recording (storing) information (data).

Primary Storage

• It is directly accessable by CPU
• It is volatile in nature
• All instruction are stored in primary memory before it can be uesd for processing
• It is fastes among all type of memory
• It has small storage space

Primary storage (or main memory or internal memory), often referred to simply as memory, is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required.

Secondary Storage

• It non-volatile ,that is, data remain stored even when the computer is switched off.
• It is slower than primary memory
• It has large storage space

Secondary storage (or external memory) 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. In modern computers, hard disk drives are usually used as secondary storage.

Tertiary Storage

• It is slower than secondary memory
• Generally used to store large amount of data
• It needs robotics mechanism to insert and remove
• Used in supercomputer as accessing data is slow from Tertiary Storage Device

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 primarily used for archival of rarely accessed information since it is much slower than secondary storage. This is primarily useful for extraordinarily large data stores, accessed without human operators.

Off-line storage

• Pen drive is an example of off-line storage device
• It reqiures human operater to insert and remove
• It is portable and can be carried with ease

Off-line storage is a computer data storage on a medium or a device that is not under the control of a processing unit.The medium is recorded, usually in a secondary or tertiary storage device, and then physically removed or disconnected. It must be inserted or connected by a human operator before a computer can access it again. Unlike tertiary storage, it cannot be accessed without human interaction.

Input

Input devices are devices that bring information into a computer. Information and commands are issued to the computer by way of input devices. Input device is used to insert data and instructions for processing in the computer.
Examples of input devices include the keyboard, mouse, modem, joystick, digitizing pen and tablet, microphone, touch screens, scanner, camera.

Output

Output devices are devices that bring information out of a computer and present data in a form that people can understand.
Examples of output devices include monitors, printers, and pen plotters.

Types of Computer

Types of Computer

Since the invention of computers from first generation and fourth generation computers, they have been classified according to their types and how they operate that is input, process and output information.
Computer types can be divided into 3 categories according to electronic nature. Types of computers are classified according to how a particular Computer functions.

The types of computer are

• Analog Computers
• Digital Computers
• Hybrid Computers
Analog Computers
• It uses discontinuous analog signal
• Used in Scientifics research
• It is programmed to perform arithmetic and logical operations

Analog types of Computer uses what is known as analog signals that are represented by a continuous set of varying voltages and are used in scientific research centers, and hospitals.
With analog types of computer values are represented by physical measurable quantities e.g. voltages. Analog computer types program arithmetic and logical operations by measuring physical changes i.e. temperatures or pressure.

Digital Computer
• Have two state 0 and 1(On and Off)
• It works on high speed discrete signal of (0 or 1)

With these types of computers operation are on electrical input that can attain two inputs states of ON=1 and state of OFF = 0. With digital type of computers data is represented by digit of 0 and 1 or off state and on state. Digital computer type recognizes data by counting discrete signal of (0 or 1) they are high speed programmable; they compute values and stores results.

The Digital Computer is divided into Four Categories
1. Microcomputers
2. Minicomputers
3. Mainframes
4. Supercomputers

Microcomputers
• Microcomputer is known as Personal Computer or PC in short
• First introduced by IBM
• It was called micro as CPU was created on a single chip called ‘microprocessors.’

The microcomputer is also known as the "Personal Computer". IBM introduced and marketed
the first widely available, commercialized microcomputer named the “IBM PC” where PC stood for Personal Computer. IBM PC became the standard against which all microcomputers were compared and developed, the “PC” helped provide a name for the industry to grow.
The category is termed “micro” because the fundamental component that allowed the categories development was the CPU created on a single chip .The lower costs helped in the development and production of the CPU and various components of the microcomputer allowed microcomputers to become a broad market general purpose computer.
The general appeal or focus of microcomputers on the individual’s enjoyment and productivity has been a key factor in the microcomputer developments and enhancements over the years.

Microcomputers can be grouped into five smaller groups

1. Workstation
2. Desktop
3. Server
4. Laptop and
5. Notebook.
Each referring to the physical usage of the machines and not necessarily the power.

Workstation generally refers to machines used for intensive calculations on designs such as architecture and buildings.
Desktop generally refer to machines used by business people for word processing, spread sheeting etc, and are physically placed onto a desk.
Server: A computer, or a software package, that provides a specific kind of service to client software running on other computers. The term can refer to a particular piece of software, such as a WWW server, or to the machine on which the software is running.
The Laptop and the notebook are portable machines. Laptops generally are bigger and clumsier due to the power supply being encased in the box holding the CPU.
The Notebook is generally smaller. Notebooks and laptops can work on batteries allowing the user to work with it in aeroplanes, in the car and places computers are not generally available.

Minicomputers
• Access to more Storage space
• Used to access large amount of data simultaneously
• Mainly used in medium size organization
Faster than the microcomputer with access to more storage space and more input and output devices, the minicomputer is used when large groups need access to data simultaneously. The minicomputer can do this because the hardware is designed for plugging in more devices, and the C.P.U. and support chips are designed more for this kind of work than the microcomputers.
Minicomputers are used by medium sized business and small sites of large organizations. They are also used in factories to control automated assembly lines.

Mainframes
• Have more powerful processor
• Used in large organization
• Capable of processing large amount of data simultaneously
Mainframes have more access to storage space and to input/output devices. To work with these extra devices mainframes also have more powerful 'processors'. This power is useful and required by large corporations who have large amounts of data to Process.

Supercomputers
• Supercomputers have multiple CPU and Processor.
• Mainly used for research and Weather Forecast, natural speech recognition

Supercomputers have been developed from the processing requirements of advanced research projects by engineers, scientists and more recently by other research fields. The Supercomputer is a title generally given to computers with processing power well exceeding those of the fastest mainframes and its focus is processing data and manipulation of the data. A significant difference between mainframes and supercomputers is the primary focus of super computers on processing capabilities independent of the many varied input/output devices expected on mainframes.
The major cause for the development of super-class computers has been the continuing Need in the scientific community for faster and faster calculations. Scientists working on atomic physics, computer intensive calculations such as natural speech recognition continue to require more and more computational speed to test their theorems.

Hybrid Computer
• Combination of both analog and digital computer
• It is used to convert the signal from analog to digital and digital to analog

Hybrid computer types are very unique, in the sense that they combined both analog and digital features and operations. Hybrid computers operate by using digital to analog converter and analog to digital converter. By linking the two types of computer above you come up with this new computer type called Hybrid computer.

2. Computer Hardware-CPU, I/O Devices, Storage Devices, Memory

The hardware of computer is divided into three broad categories:

1. Processor/Processing Unit
2. Memory
3. I/O (input/output).

Processor
The processor is the part of the computer that actually does the computations. This is sometimes called an MPU (Main Processor Unit) or CPU (Central Processing Unit or Central Processor Unit).
A processor typically contains an Arithmetic & Logic unit (ALU), Control Unit (CU).

Arithmetic & Logic Unit (ALU)
An arithmetic & logic unit (ALU) performs integer arithmetic and logic operations. It also performs shift and rotate operations and other specialized operations. Usually floating point arithmetic is performed by a dedicated Floating Point Unit (FPU), which may be implemented as a co-processor.

Control Unit (CU)
Control units are in charge of the computer. Control units fetch and decode machine instructions. Control units may also control some external devices.

Main Storage
Main storage is also called memory or internal memory (to distinguish from external memory, such as hard drives).

RAM is Random Access Memory, and is the basic kind of internal memory. RAM is called “random access” because the processor or computer can access any location in memory (as contrasted with sequential access devices, which must be accessed in order). RAM has been made from transistors, integrated circuits, magnetic core, or anything that can hold and store binary values (one/zero, plus/minus, open/close, positive/negative, high/low, etc.).

Static RAM is called static because it will continue to hold and store information even when power is removed. Magnetic cores are examples of static memory.
Dynamic RAM is called dynamic because it loses all data when power is removed. Transistors and integrated circuits are examples of dynamic memory.

ROM is Read Only Memory (it is also random access, but only for read). ROM is typically used to store things that will never change for the life of the computer, such as low level portions of an operating system.



Data storage device
Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data used for computing for some interval of time. Computer data storage provides one of the core functions of the modern computer, that of information retention. It is one of the fundamental components of all modern computers A data storage device is a device for recording (storing) information (data).

Primary Storage
• It is directly accessable by CPU
• It is volatile in nature
• All instruction are stored in primary memory before it can be uesd for processing
• It is fastes among all type of memory
• It has small storage space

Primary storage (or main memory or internal memory), often referred to simply as memory, is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required.

Secondary Storage
• It non-volatile ,that is, data remain stored even when the computer is switched off.
• It is slower than primary memory
• It has large storage space
Secondary storage (or external memory) 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. In modern computers, hard disk drives are usually used as secondary storage.

Tertiary Storage
• It is slower than secondary memory
• Generally used to store large amount of data
• It needs robotics mechanism to insert and remove
• Used in supercomputer as accessing data is slow from Tertiary Storage Device

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 primarily used for archival of rarely accessed information since it is much slower than secondary storage. This is primarily useful for extraordinarily large data stores, accessed without human operators.

Off-line storage
• Pen drive is an example of off-line storage device
• It reqiures human operater to insert and remove
• It is portable and can be carried with ease

Off-line storage is a computer data storage on a medium or a device that is not under the control of a processing unit.The medium is recorded, usually in a secondary or tertiary storage device, and then physically removed or disconnected. It must be inserted or connected by a human operator before a computer can access it again. Unlike tertiary storage, it cannot be accessed without human interaction.




Input
Input devices are devices that bring information into a computer. Information and commands are issued to the computer by way of input devices. Input device is used to insert data and instructions for processing in the computer.
Examples of input devices include the keyboard, mouse, modem, joystick, digitizing pen and tablet, microphone, touch screens, scanner, camera.

Output
Output devices are devices that bring information out of a computer and present data in a form that people can understand.
Examples of output devices include monitors, printers, and pen plotters.

Management Information System

An 'MIS' is a planned system of the collecting, processing, storing and disseminating data in the form of information needed to carry out the functions of management. In a way it is a documented report of the activities that were planned and executed. According to Philip Kotler "A marketing information system consists of people, equipment, and procedures to gather, sort, analyze, evaluate, and distribute needed, timely, and accurate information to marketing decision makers."
A Management Information System (MIS) is a system or process that provides information needed to manage organizations effectively . Management information systems cover the application of people, documents, technologies, and procedures used by management to solve business problems such as costing a product, service or a business-wide strategy. Management information systems are distinct from regular information systems in that they are used to analyze other information systems applied in operational activities in the organization. Academically, the term is commonly used to refer to the group of information management methods tied to the automation or support of human decision making, e.g. Decision Support Systems, Expert systems, and Executive information systems.

Management is usually defined as planning, organizing, directing, and controlling the business operation. Management is the process of allocating an organization's inputs, including human and economic resources, by planning, organizing, directing, and controlling for the purpose of producing goods or services desired by customers so that organizational objectives are accomplished. If management has knowledge of the planning, organizing, directing, and controlling of the business, its decisions can be made on the basis of facts, and decisions are more accurate and timely.

Information is what is used in the act of informing or the state of being informed. Information includes knowledge acquired by some means. When information is entered into and stored in a computer, it is generally referred to as data. After processing (such as formatting and printing), output data can again be perceived as information. When information is packaged or used for understanding or doing something, it is known as knowledge.

A system is a combination or arrangement of parts to form an integrated whole. A system includes an orderly arrangement according to some common principles or rules. A system is a plan or method of doing something.