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Join the session on Boolean Algebra & Logic Gates for Digital Circuits & Systems

Direct Link : http://tinyurl.com/yewbw3t

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Real Time or Reactive Systems are systems subject to time constraints. These are bounds which act as operational deadlines for processes.

While driving a vehicle, if we apply the breaks for a particular time(bound), the car stops. Similarly, if a bound is met the process stops.

A system may be classified as soft real time(deadlines met generally) or hard real time(deadlines met deterministically).

A soft real time may only lead to decrease in service quality while a heard real time may lead to complete failure of the system on meeting a bound.

Real time systems are used to guarantee that deadlines are met, are where throughput is not the major aim.  These are used largely in medical equipment, missile systems, etc.

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Distributed Computing Systems consist of multiple computers which together form & communicate through a computer network.

A program is divided(distributed) into many individual jobs, each of which is then solved by the computers in the network. One job, per computer.

This is in contrast to parallel systems, where the job is divided but solved by the same computer.

Hence, in case of parallel systems, we have the same memory but different processes, while in case of distributed systems, there are different processes on different memory units.

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(A4) Parallel Computing Systems:

In parallel systems, large jobs are divided into smaller ones which are then processed simultaneously(hence, the name parallel). Since, the task is broken down, the efficiency largely increases.

Parallel computing has a number of advantages over other paradigms:

-It leads to a large increase in efficiency.

-It helps in power consumption.

It is the hence, the most dominant paradigm in computer architecture.

The disadvantages regarding parallel computing are:

-The processes difficult to write.

-Gives more scope for bugs to crawl in.

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(A3) Time Sharing Systems

The main idea of time sharing systems is to allow a large number of users to interact with a single computer(system) concurrently.

Hence, it extended the idea of multiprogramming to allow multiple terminals with each-in-use terminal to be associated with one or more jobs.

Hence, the there are spaces for more than one user, each associated with a program or more.

The main objective of these systems is to minimize the response time to user commands.

(and lead to interactive work)

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In Multiprogramming Batch systems, when one job waits for the completion of an I/O operation, another is executed.

A multiprogramming system is responsible for:

-starting jobs
-taking I/P for jobs
-switching between jobs
(& ensuring protection while doing so)

Classified jobs as foreground and background jobs.

When a foreground jobs encounters an operation requiring input or giving output to the user, a background job is executed.

Hence, more than one program could be executed, but, by the same user.

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(A) Computer Architecture Paradigms

(A1) Simple Batch Systems

Simple Batch systems or just Batch systems process jobs bundled together, leading to an increase in efficiency.

When a job is processed, the system transfers the entire control over to it. Once it is done, the control shifts to the next job, and so on.

This hence, has the following ADVANTAGES:

-maximum processor utilization
-the setup time for jobs is saved
-performance increases, since, the job are sequenced together

It also, however, has a few DISADVANTAGES:

-difficult to debug
-one job affects all the pending jobs.
- job could enter an infinite loop, and others will never be processed.

Hence, we would need some protection scheme for the pending jobs, in case a job is affected/corrupt.

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Operating Systems – INTRODUCTION TO OS

We’ve heard of applications that run on Windows or Mac and so on. Thus Windows or Mac act as hosts for our computer applications.
Hence, The Operating System is an interface between the user and the hardware, and the host for the applications & software.

Thus, the applications need to access the services of the OS. This is done through what are called APIs(Application Programming Interfaces) or system calls.

The central component of the OS is the kernel. The kernel is the bridge between the applications & the hardware. Hence, It allows applications to process data at the hardware level. It can also control a process’ access to the computer memory.

Sometimes, the kernel is used to limit a certain process’ access to memory, a phenomenon called memory allocation/protection. This can be achieved by Segmentation & Paging.

The kernel & kernel extentions are alloted certain memory space, which, together with the user space alloted for all user apps, form the Virtual Memory. Virtual Memory is the key to multitasking kernels.

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The example below explains inheritance, an important property of OOP languages.

We have three classes: living, animal & dog. The dog inherits all the characteristics of living & animal base classes however, the plant does not(being an instance of just the living class).

#include<iostream>
using namespace std;
class living
{
      int energy;
      public:
                void getenergy()
                {
                     cout<<"Gets energy"<<endl;
                     }
};
class animal:public living
{
      int feet;
      public:
                void move()
                {
                     cout<<"It moves"<<endl;
                     }
};
class dog:public animal
{ 

      int tail;
      public:
                void bark()
                {
                     cout<<"It barks"<<endl;
                     }
};
int main()
{
    living plant;
    plant.getenergy(); 

    dog phoenix;
    phoenix.getenergy();
    phoenix.move();
    phoenix.bark(); 

    system("pause");
    return 0;
}

The dog inherits the properties of animal which inherits the properties of living. Hence, this inheritance is an example of “Multi-level” inheritance.

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The diode’s we’ve been talking about all this time do have some really cool applications in signal processing, power supply & a lot of other places.

And yes, the AOD stands for “Applications of Diodes” & we’re gonna use that for the rest of the apps as well.

Diodes are used in rectifiers which are devices that convert an AC to a DC signal, not a pure dc signal though… And as a matter of fact, the only source of pure DC is a battery.

And this process of converting AC to DC is called rectification. Consider a simply sine wave as the input from an AC source. Then the following summarizes the overall process of rectification…

So, there is no output for the negative half as the diode is in the reverse bias condition(considered OFF). Also, the circuit we use here is just what the half wave rectifier really is.

Now, considering the two halves collectively, we get an output signal like so…

Notice here that the peaks of the positive cycle appear at equal distances, and this distance is same for the input & the output signal. Hence, the frequency of the signal does not change.

(f_in=f_out)

Getting into the mathematical view of things, we can now calculate the RMS & Average values of the voltage for our new output signal.

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