Application of microprocessor

Microprocessors field wide applications in the fields of instrumentation,communication,data processing,industrial process instrumentation,commerce and consumer products.
A few exemplifying applications in each field are given below:
1. Instrumentation: Automatic test equipment,electronic instrument;and analytical,chemical,and medical equipment.
2. Communication: Remote terminals,programmable controller, switching systems,multiplexers,message handling and error detection.
3.Data processing: programmable calculators;peripheral processors,I/O controllers and communication interface.
4. Industrial: Data acquisition system,numerical control and environmental monitoring process control and instrumentation.
5.Commercial: Inventory control system,payroll,banking and financial system and auto-transaction system.
6.Consumer: Education systems,intelligent toys,games,automotive system and programmable appliances.
The electronic industry has been benefited by the introduction of microprocessors in the three broad areas of flexibility,reliability and cost.Mini or small business computer industry,the electronics industry and the large-scale data processing industry are the major beneficiary from introduction of microprocessor

Hard Disk

hard disks are on-line storage devices.The term on-line means that the device (hard disks) is permanently connected to the computer system.when computer is on,the device (hard disks) is available to store information or to give information.Hard disks are used as secondary memory for mass (bulk) storage of information permanently.They store program,data,operating system,compilers,assemblers,application programs,database,etc.

A hard disk is made of aluminum( or other metal or metal alloy) with a thin coating of magnetic material (iron oxide) over it,standard size of hard disks is 3.5 inch.The 2.5 inch disk are used in portable computers.Hard disks and read/write heads are kept in a sealed,air filtered enclosure.This technique is known as winchester technique.Hard disks together with read/write heads,access mechanism and driving motor constitute an unit called hard disk drive platter.It cannot be removed or inserted into a hard disk drive unit.Hard disk drive unit under discussion is of large capacity,and is used as secondary memory.Recently removable hard disks and external hard disks of smaller capacity for backup memory have also been developed.

To increase the storage capacity several hard disk(platters) are mounted on common drive to constitute a disk pack,as shown in fig.The set of all tracks at the same distance from the spindle on the record able surface of the disk pack will lie on the surface of an imaginary cylinder.All the tracks which lie on a cylinder have same number.for example,track-10 of each recordable surface of the pack will lie on the cylinder which is numbered as cylinder-10.The disks are addressed by drive number(because more than one drives are used in a computer),cylinder number (i.e. track number),surface number and sector number. 

Unions

Unions are a concept borrowed from structures and therefore follow the same syntax as structures.However,there is major distinction between them of storage.In structures,each member has its own storage location,whereas all the members of a union use the same location.This implies that,although a union may contain many members of different type,it can handle only one member at a time.

a union can be declared using the keyword union as follows:

union item

{

int m;

float x;

char c;

}

code;

The declares a variable code of type union item.The union contains three members,each with a different data type.However,we can use only one of them at a time.This is due to the fact that only one location is allocated for a union variable,irrespective of its size.

The compiler allocated a piece of storage i.e large enough to hold the largest variable type in the union.

Searching and Sorting

Searching and sorting are the two most frequent operations performed on arrays.Computer scientists have devised several data structures and searching and sorting techniques that facilitate rapid access to data stored in lists.
sorting is the process of arranging elements in the list according to their values,in ascending or descending order.A sorted list is called an ordered list.sorted lists are especially important in list searching because they facilitate rapid search operations.Many sorting techniques are available.The three simple and most important among them are:

• Bubble sort
• Selection sort
• Insertion sort

Other sorting techniques include shell sort,Merge sort and Quick sort.
Searching is the process of finding the location of the specified elements in a list.The specified elements is often called the search key.If the process of searching finds a match of the search key with a list elements value,the search said to be successful;otherwise,it is unsuccessful.The two most commonly used search techniques are:

• Sequential search
• Binary search

While statement in c and C++

The simplest of all the looping structures in C is the while statement.we have used while in many of our earlier programs.The basic format of the while statement is

 while(test condition)

 {

           body of the loop

}

The while is an entry-controlled loop statement.The test-condition is evaluated and if the condition is true,then the body of the loop is executed.After execution of the body,the test-condition is once again evaluated and if it is true,the body is executed once again.This process of repeated execution of the body continues until the test-condition finally becomes false and the control is transferred out of the loop.On exit,the program continues with the statement immediately after the body of the loop.

The body of the loop may have one or more statements.The braces are needed only if the body contains two or more statements.However,it is a good practice to use braces even if the body has only one statement.

example:

sum=0;

n=1;

while(n<=10)

 {

 sum=sum+n*n;

n=n+1;

}

printf("sum=%d\n",sum);

ELECTRICAL SYMBOL

Pulse width Modulation (PWM) Operation in S7200 PLC

The PWM function provides for variable duty cycle outputs.The cycle time and the pulse width can be specified in a time base of either microseconds or milliseconds.The cycle time has a range either from 50 microseconds to 65,535 microseconds,or from 2 milliseconds to 65535 milliseconds.The pulse width time has a range either from 0 microsecond to 65,535 microseconds,or from 0 millisecond to 65,535 milliseconds.when the pulse width is specified to have a value greater or equal to the cycle time value,the duty cycle of the waveform is 100% and the output is turned on continuously.when the pulse width is specified as 0, the duty cycle of the waveform is 0% and the output is turned off.If a cycle time of less than two time units is specified,the cycle time defaults to two time units.
There are two different ways to change the characteristics of a PWM  waveform:
with a synchronous update and with an asynchronous update.

BACKWARD WAVE OSCILLATOR

Backward wave oscillator (BWO) is a microwave continuous wave (CW) oscillator with excellent tuning capability and frequency coverage range. BWO is similar in construction and operates on the same principle of electron beam-RF field interconnection,generally employing a helical slow wave structure.It can be thought of as a short,thick TWT.
Operation:
The electron beam from the electron-gun cathode is focused by an axial magnetic field.If transients have resulted in starting RF oscillation,these travel through the helix and interact with electron beam.Bunching takes place increasing in completeness from the cathode to the collector and interchange of energy between the electron beam and the RF wave occurs exactly in the same way as in TWT. since BWO does not have an attenuator,there will be oscillation  due to reflection from an imperfectly terminated collector end of the helix.The reflected wave results in a backward wave.