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Lesson 5: Managing Input and Output Functions.

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    We have oftenly used two functions printf and scanf for writing of data and reading of data from terminal. Each program that uses a standard input/output function must contain the statement

    #include<stdio.h>

    However, this is not necessary for printf and scanf, stdio.h stands for standard input-output header file.

Reading a Character:

        Reading a single character from terminal can be done by using the function getchar().

        ex. char name;

              name=getchar();

        When this statement is encountered, the computer waits until a key is pressed and then assigns this character as a value to getchar function. In the above example if key H on the keyboard is pressed while execution of progra,, it will be stored in the variable name.

    Program:-

    #include<stdio.h>

    main()

    {

        char answer;

        printf("Would U like to know mu name?\n");

        printf("Type Y for yes and N for no");

        answer=getchar();

        if(answer=='y' || answer=='Y')

        printf("\nMy name is Computer");

        else

        printf("U are good for nothing");

    }

   Program:- For testing whether entered character is numeric/alphanumeric or alphabetic using                       character type function.

    #include<stdio.h>

    #include<ctype.h>

    main()

    {

        char character;

        printf("Press any key\n");

        character=getchar();

        if(isalpha(character)>0)

        printf("The character is a letter");

        else if(isdigit(character)>0)

        printf("The character is a digit");

        else

        printf("The character is alphanumeric");

    }

   Writing Character:

                    Like getchar(), there is a function putchar() for writing characters one at a time.

                     ex. answer='Y';

                           putchar(answer);

                            this will display Y on the screen.

    Program:- getchar() example.

    #include<stdio.h>

   #include<ctype.h>

   main()

   {

      char alphabet;

      printf("\nEnter an alphabet");

      putchar("\n);

      alphabet=getchar();

      if(islower(alphabet))

      putchar(toupper(alphabet));   

       else

        putchar(tolower(alphabet);

    }

   Formatted Input:

                        Formatted input refers to an input data that has been arranged in a particular format.

   Consider the following data:

                                             15.57 123 Radha

                                                                        These are three types of data. First should read into a variable float, the second into int and the third into char. This is possible in C using scanf function.

    scanf("control string",arg1,arg2,...argn);

    Control string: It must contain a format specification consisiting a conversion character % and a type specifier and an optional number specifing fieldwidth.

    %wd -- Field Specification for reading an integer number.

    Consider following examples:

    1) scanf("%2d%5d",&num1,&num2)   

                    Here you can assign maximum 2 digit integer number to variable num1 and 5 digit to                                                                                                                                   variable num2.

    2) scanf("%2f",&amt);

                    Here you can read a number with maximum two decimal places and assign it to variable                                                                                                                                                  amt.

   Formatted Output:

                printf function can be effectively used to print formatted output on the screen.

                 printf("control string",arg1,arg2,...argn);

                 Control string consists of three types of items

                  1) Characters that will be printed on screen as they appear

                      ex. printf("Hello! How R U?");

                  2) Format specifications that define the output format for display of each item.

                      ex. printf("%5d",x);

                  3) Escape sequence characters.

                      ex. printf("\n");          

                     Output of real numbers:-

                        ex:-y=98.7654

Format Output
printf("%7.4f",y); 98.7654
printf("%7.2f",y); 98.77
printf("%-7.2f",y); 98.77
printf("%f",y); 98.7654

 

   Printing of Strings:

                                        The effect of a variety of specifications in printing a string "NEW DELHI - 111001" containing 16 characters is as below

Specification Output
%s NEW DELHI _ 111001
%20.10s NEW DELHI
%.5s NEW D
%-20.10s NEW DELHI

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