CSE NOTES

Process control block -Each process is represented in the operating system by the process control block also called as task control block. -It contains many pieces of information associated with a specific process include these Process states: The state may be new/ready,running,waiting,haltered and soon. Program counter: The counter can be indicate to the address of the next instruction to be executed for this process. CPU registers: The register vary in number and type depending in the computer or architecture .they includes the accumulator,index register,stack pointer , general purpose of register. Memory management information: It may be includes such information as the value of the base and limit register, the page tables or segment tables depending on the memory system used by the operating system. Accounting information: It includes the account of the CPU and real time used,time limits account number,job or process number and soon. I/O status inf

-Process state means current activity of process. -When process is execute it changes the state generally state of process is determine by the current activity of process. -Each process may be in one of the following state. new- the process is being is oriented. ready- the process is waiting to be assigned to the processor. waiting - the process is waiting for some event (I/O operation) to occur. running - the process is being executed.  terminated -the process as finished the execution. process state diagram: -The pictorial is represented to the process changing from one process to another process during       there  execution is known as process state diagram. -A process can be change for one process in the following manner. new ready: The operating system(os) create a process and prepares the process to be executed ,then the os moved the process into the ready queue.  ready running: When it is time to select a process to run, the os selects one jo

Queries in SQL Data types character: -This types of data types store the characters string in fixed length. -The size in brackets determine the no of characters the shell can hold. -character data types is 255 characters. var character(size)/var char 2 (size): -This character is used to store variable length alpha numeric data. -Var char is 2000 character. date: -Date data type is used to represent to the data / time. -The standard. format is dd/mm/yy. Number: -The number data type is used to store number no of any magnitude may be stored up to 38 bit.  

Data Model -Data model is used to describe of the structure of the database and to hide of the storage details and present the users with the conceptual view of the database. -In other words how to store data in the database is known as data model. -There are three types of data model:                                                             hierarchical data model                                                             network data model                                                             relational data model Hierarchical data model: -hierarchical data model is nothing but a incurred tree like structure. -It represents data and relationship between data item in the model of the involved tree. -It is the most popular data model other system based on the this model. -It is very simply to con street and operate on the simple language is used. Network data model: -It represents data in a network structure. -In the network data model data are

E-R diagram -E-R diagram is the entity relationship diagram. -E-R diagram can express the logical structure of the database graphically. -E-R diagram can consist of the following major components. -The entity sets are represented by the rectangular. -The attribute are represented by the ellipse. -The relationship are represented by the diamond and rhombus. -Line is used to link attribute to entity sets and entity sets to relationship sets. -double ellipse is represented to composite attributes. -Dotted ellipse is represented to dotted derived attributes. It is represented to composite attributes. -Key attributes. -Double rectangle represented to work of entities. -Double line indicate to the particularization of an entity set in the relationship sets. -One to

Mapping constraints  -A mapping constraints is data constraints that express the number of entity to which another entity can be related via a relationship sets.  -It is most useful in describing relationship sets that involve more than two entity sets.   -There are four types of mapping constraints. -one to one  -one to many -many to one  -many to many one to one: Let us consider two entity sets A and B. An entity in A is associated with at most one entity in B.An entity in B is associated with at most one entity in A. one to many: Let us consider two entity sets A and B. An entity in A is associated with any number (0 or more) of the entity in B and An entity in B is associated with at most one entity in A. many to one : let us consider two entity sets A and B. An entity in A is associated with at most one entity in B and an entity in B is associated with any number of the entity in A

Attribute  -Properties or character of the entity is called attribute  the attribute are the descriptive properties   proceed by the each member of the entity set  -ex The possible attribute of the customer entity are customer city, customer id, loan. \-There are 4 types of the entity :                                                      -single value and multi value attributes                                                       -simple and composite attributes                                                      -derived attributes                                                       -null attributes single value attributes: In the single value attributes there are the value for the specific entity. multi value attributes: In the multi value attributes there has a set of value for a specific entity. ex:  simple attribute: It can,t be divided into two sub parts. ex: composite attributes: The composite attribute which is composed

Entity relationship model(E-R model) -Entity relationship model consists of the entities and relationship. -It was developed to facility database designed by allowing specification of the enterprise schema. -the enterprise schema consists of the overall logical structure of the database. -The E-R model is very useful  in mapping the meaning integration of the recall world enterprise on the conceptual schema. -The E-R data model is three basic option :        _Entity set        _relationship set        _Attributes   -It is use for the conceptual design of the database application. Entity:  An object which has a some physical existence is called entity. Relationship: A relationship is a associate among several entity. Entity set are relationship set Entity set: -A group of similar types of entities is called is called entity sets. -Let T be a entity set e1,e2,e3..........en.   e1,e2,e3,,,,,,,,en are the same types of entity. -Or a entity set is a s

Necessary condition for Deadlock A deadlock system contains process and resources satisfy by the following the 4 condition. Mutual exclusion: -It means resources are (at least one) in non shareable mode only. -It means only one process at a time can use the resources . -If some other process request the resources than the process will must wait until the resources has been released. -e.g A printer is a non shareable device bcz the printer can,t be share by the multiple no of process at a time. Hold and wait: -each and every process in deadlock state and must held at least one resources and waiting for other resources which again held by other process. -p1,p2,p3 are 3 process and r1 , r2 , r3 are`3 resources each process can must hold resources.      in this diagram p1 is holding the resources r3 and waiting for the resources r1 and p2 is holding the resources r1 & r4 and waiting for the resources r2 & r3.        p3 is holding the resources r2 and wai

Deadlock -In the multi programming environmental several process may compete for finite no of resources. -A process request resources if the resources is hot available at that time a process enter to the wait state and waiting process may never changes its state bcz resources requested are held by other waiting process.                               This situation to called deadlock   if process are p1 and p2 or resources are r1 and r2 .process p1 request to resources r1 and the resources r1 is held by the process p2, process p2  request r1 is held by the process. p2 process request r2 but the resources r2 is held by the process p1. In this situation two process can,t start their operation.                  so process are enters in waiting state , this situation to called deadlock situation.                                  

Network types -The computers are interconnected to information among them which can for mean a computer N/w. -the computer network type is 3 types:                                                                  1.LAN(Local area network)                                                                  2.MAN(Metropolitan network)                                                                  3.WAN(Wild area network) LAN(Local area network) -LAN is usually private own network in which the computers are interconnected in a room or so many in a building or so many building on a campus with in a  specific geographic area depended the on organisation.  -LAN can be as simple as two computer pointer in some one office and it can extent to through out of the company.   -now days LAN size is the imitated to few kilometers.  -LAN are designed to allow resources to be share among them  multiple number of valid user. -LAN is different for other network by their transmissi

Line configuration -it is refers to the way two or more communication devices to attach to the link. -a link is a physical  communication path which is transfer the data one device to another device. -it is the two types of line configuration:                                                                    1. point to point line configuration                                                                    2. multi point line configuration point to point line configuration: -point to point line configuration is provided to  dedicated link between the two devices. -the entire capacity of the link and challenge for data transmission between the two devices. -most of the point for configuration need actual length of wire two ends. multi point line configuration:  the multi point line configuration is known as in which more than one specific devices share a single link depending upon the sharing of the channel capacity.                                   

TOPOLOGY -IT means the computer network is layout either physically or logically two or more devices connected to the link. -Two or more link indicate to the topology structure.it is the geometric representation of the relation of all the link and linking devices to each other. types of topology 1.mesh topology 2.star topology 3.ring topology 4.bus topology 5.hybrid topology 1.mesh topology: the mash topology has a dedicated point to point  link to every other devices. advantages:   -the use of dedicated link guaranties that each connection can Carrie   it,s own data thus elementary data to the traffic problem that can occur when the link can share by the multiple devices. -the mesh topology is the robust. if one link be come useless it did,t indicate to the whole network out of order. disadvantages: -the mash topology have a large no of cabling and large no of i/o points are required. -as every device must be connected with every other devic