Modem

Modem

•Do modulation

•D2A and A2D converter

•Mode+demod=modem

Different Types

Different Types

The many different types of information systems can be divided into categories based on where they are used in the hierarchy of an organization.

What is an Information System?

What is an Information System?

Many organizations work with large amounts of data. Data are basic values or facts and are organized in a database. Many people think of data as synonymous with information; however, information actually consists of data that has been organized to help answers questions and to solve problems. An information system is defined as the software that helps organize and analyze data. So, the purpose of an information system is to turn raw data into useful information that can be used for decision making in an organization.

Typical Components of Information Systems

While information systems may differ in how they are used within an organization, they typically contain the following components:

1. Hardware: Computer-based information systems use computer hardware, such as processors, monitors, keyboard and printers.
2. Software: These are the programs used to organize, process and analyze data.
3. Databases: Information systems work with data, organized into tables and files.
4. Network: Different elements need to be connected to each other, especially if many different people in an organization use the same information system.
5. Procedures: These describe how specific data are processed and analyzed in order to get the answers for which the information system is designed.

The first four components are part of the general information technology (IT) of an organization. Procedures, the fifth component, are very specific to the information needed to answer a specific question.

Structure of C program and Why we put braces () with main

Structure of C program

•A C program consist of following parts.

•1- preprocessor Directive (#include<iostream.h>)

•2-main function                                                 void main ()

•{   

•  program body

• }

Why we put braces () with main

•Braces tells the compiler that the word “main” is name for a function. Otherwise compiler will consider it is name of some variable or identifier.

•If braces are empty it means function do not take input from some other function

•Like void main()

•If braces are not empty then it means function may take input arguments.

•Like void main(int a , char b ) means this funciton can take two input arguments.

Example program and Rules for writing a program

Example program

•#include<stdio.h>

•#include<conio.h>

•void main()

•{

•  printf”Hellow world";

•getch();

•}

•

Rules for writing a program

•All the names of the variables and other words should be in lower case

•The first function of the program should be main.

•All the program should be in medium braces {}

•After each instruction of the program we should put semicolon but no semi colon after main, preprocessor directive and braces because they are a part of program but not executed like other instructions.

Comments in a program and Data types

Comments in a program

•Comments are the lines of the program which are ignored during the program execution.

•When a programmer write a program he adds some comments with it to make the program easy to understand.

•Comments may be single line or multiple line.

•Single line comments are proceeded by //

•Multiple line comments should be within this symbol.

•/*       coments     */

Data types

 •Any type of data that is used in c/c++ program has its type with the help of which compiler can recognize it and can reserve space for it in memory.

•Basically two types of data is used in c/c++

•Variable and constant

Data types used in c program and int

Data types used in c program

1- integer variable Int

2- character variable

Char

3- floating point variables

Float

4- Enumerator

Enum

5- class

Class

6- string

Char []

int

•This data type is used to save integer values

•E.g. 2, 25 ,567 etc.

•C++ compiler use 4 bytes to save int

•In old compilers int was of 2 bytes so its range was -32767 – 32768

•It comes in three values, int, short int, long int

•Length of data depends on compiler, but short int is at least 2 bytes and long int is at least 4 bytes