Conductors, Semiconductors, Insulators

Solids can be classified on the basis of electrical conductivity as:
1) Conductors
2) Semiconductors
3) Insulators

Conductors: The Substances which easily allow electric current pass through them are called conductors. E.g. Copper, Aluminium has large no. of free electrons.

Conductors contain no forbidden energy gap between valance band and conduction band. They overlap each other as shown in the given image. Without supplying any additional energy valance electrons become free electrons which make metals like Copper, Aluminium good conductors of electricity.

Capacitors

The electronic components that are used to store the charge are called Capacitors. This capability of capacitors to store the energy (Charge) is called capacitance. Capacitance is measured in Farads (F). Farad is a very high unit of capacitance. Lower units are Micro Farad (µF) and Pico Farad (pF).

Capacitor consists of two conducting plates that are separated by an insulating material which is known as dielectric. Capacitor offers very low impedance to AC but it blocks DC. The reason behind this is that
X_C =1/2πfc and for AC frequency is 50-60 Hz but for DC frequency is 0 hence X_C= Infinite.

Capacitors are classified on the basis of die electric used between them. Some well known types of Capacitors are as Follows:

1) Mica Capacitors: These types of Capacitors are constructed with the help of two Aluminium foils separated by a mica sheet. These plates are connected to two electrodes. The entire unit is encapsulated in a plastic housing. These type of Capacitors are used for small capacitance values ranging from 5 pF to 10µF. These Capacitors can operate at up to 500V and has leakage current about 1000MΩ.


















2) Paper Capacitors: These types of capacitors are

Resistors and Their Types

The components which resist or oppose the flow of electrons in any electrical or electrical circuit is called resistor. The force by which it resists flow of current is called resistance. It is measured in Ohms (Ω). Resistors are used to limit current flowing through a circuit or to divide the voltage in a circuit.

Types of Resistors
i) Fixed Value Resistors.
ii) Variable Value Resistors.


Fixed Resistors: The Resistors whose value remain same and can’t be changed is called fixed value resistor. Fixed value resistors can be of following types:

a) Carbon Resistors: These types of Resistors are manufactured from mixture of carbon or graphite and clay. These are also made in metalized type by decomposing a homogeneous film of pure carbon or metal over glass, ceramic or any other insulating core.

 
b) Wire Wound Resistors: These types of resistors are made

Intel 8085 Block Diagram

Intel 8085 consists of following three main sections:

Arithmetic and Logical Unit:- The main function of ALU is to perform arithmetic and logical operations such as Addition, subtraction, Logical AND, Logical OR, Complement, Increment, Decrement, Shift Operations etc.

Timing and Control Unit: - Generation of timing and control signals for the execution of instructions is done by this unit. It controls and monitors flow of data between CPU and I/O devices. It works as brain for Computer System.X1, X2, Clock Out, ready, ALE, HOLD, HLDA are some examples of signals generated by this unit.

Interrupt Control Unit:- This unit handles various types of Interrupts. Its main function is to decide which interrupt to service first and how to service. It supports three Maskable Interrupts (RST 7.5, RST 6.5 and RST 5.5), one non-Maskable interrupt (TRAP) and one externally serviced interrupt (INTR).

Serial I/O Control Unit:- It is used for the serial data transmission and receiving. SID (input) is an input line and is used to receive serial data; Signal SOD (Output) is for the serial output.

Registers:-Various types of registers are used by 8085 for the temporary storage of data, manipulation of data and instructions. These registers hold data till it is either sent to I/O or an instruction execution is complete.

A) Accumulator (ACC):-It is 8 bit register and is associated with ALU. Its function is to hold one operand during instruction execution and another operand is stored in some other general purpose register or memory for arithmetic or logical operations. Result is stored in accumulator. It works as input for ALU.

B) General Purpose Registers:- 8085 make use of six 8 bit general purpose registers. These registers can be used to store 16 bit data using register pairs. Following register pairs are valid in 8085: H-L, D-E, H and L. These register pairs can’t be altered. E.g. B-D register pair can never be used.

Database Management System (DBMS) Interfaces

DBA Interface: This interface is used by the database administrator to create databases, Users, to set system parameters for changing database schema etc. Fig. given below shows admin menu where DBA is can create new user and can assign privileges to him.

Graphical User Interface: This interface represents database

Classification of Database Management System

Database Management System can be classified on several DBMS criteria.

A) On the Basis of Data Models.

Data model is a collection of high level data description that hides many low level storage details. A data Model has following three Components:
1) A Structural Part that consist of a set of rules according to which database is constructed.
2) A Manipulating Part That defines type of operations that are allowed on data.
3) A set of integrity rules that ensures that data is correct.
The Data Models are further divided into Three Categories: 

I) Object Base Data Models: Object based data models defines a database in terms of objects, their properties, and their operations .Objects of same behavior and structure belongs to a class and classes are organized into hierarchies. The operations of each class are specified in terms of predefined procedures called methods. Commonly used object based data models are:
Entity Relationship, Object Oriented, Semantic, Functional

II) Physical Data Models: Physical data models include all data artifacts that are