Formatted I/O

Formatted I/O

• An union is a user defined data type just like structure except that in union same memory space is used for all members of union.
• While printing or reading data we can specify its width, type , precision …etc.
• To perform formatted I/O operations we can use the printf and scanf family of functions.
• printf family
• printf – to print on standard output device
• fprintf – to print in a file
• sprintf – to print in a string
• scanf family
• scanf – to read data from standard input device
• fscanf – to read data from file
• sscanf – to read data from string

Format specifiers

• We can use different format specifiers such as
• Type specifier
• Width specifier
• Precision specifier
• Sign specifier
• Alignment specifier

Type specifier

• It indicates type of value to print
• %d – decimal int value
• %ld – long int value
• %f – float value
• %lf – double
• %c – char value
• %x – int value in hex format
• %o – int value in oct format
• %u – unsigned int value
• %lu – unsigned long value
• %s – string

Width specifier

• It specifies width of value to be printed.
• It is numeric value before type specifier.
• For eg %10d – will print value of 10 char width.

  #include<stdio.h>
  main()
  {
    int a=4123;
    float b=2.3;
    char c[]="CCIT";
	
    printf("\n%d",a);
    printf("\n%f",b);
    printf("\n%s",c);
    printf("\n%10d",a);
    printf("\n%10f",b);
    printf("\n%10s",c);
  }

4123
2.300000
CCIT
      4123
  2.300000
      CCIT 
  

Precision Specifier

• It indicates the no. of digits to be printed after a decimal point for float values.
• It indicates the no chars to be printed from a string.
• For int value it is ignored.
• It can be specified by using number after decimal point in format specifier.

  #include<stdio.h>
  main()
  {
    int a=4123;  
    float b=2.3123;
    char c[]="CCIT";
	
    printf("\n%d",a);
    printf("\n%f",b);  
    printf("\n%s",c);
    printf("\n%.2d",a);
    printf("\n%.2f",b);
    printf("\n%.2s",c);
  }

4123
2.312300
CCIT
4123
2.31
CC
  

Alignment Specifier

• By default values are printed as right aligned in width field.
• If we want left aligned values then - sign can be used.

  #include<stdio.h>
  main()
  {
    int a=4123;
    float b=2.3123;
    char c[]="CCIT";
	
    printf("\n%10d only",a);
    printf("\n%10f only",b);
    printf("\n%10s only",c);
	
    printf("\n%-10d only",a);
    printf("\n%-10f only",b);
    printf("\n%-10s only",c);
  }

4123 only
  2.312300 only
      CCIT only
4123       only
2.312300   only
CCIT       only
  

Sign Specifier

• It indicates to always print a sign i.e. – sign before a negative no and + sign before a positive no.
• This can be achived by using a +sign in format specifier.

  #include<stdio.h>
  main()
  {
    int a=4123,b=-322;
	
    printf("\n%d",a);
    printf("\n%d",b);
	
    printf("\n%+d",a);
    printf("\n%+d",b);
  }

4123
-322
+4123
-322 
  

Formatted Input

• If width specifier is used in scanf function then it scan data of specified width.

  #include<stdio.h>
  main()
  {
    int a,b,c;
    printf("Enter Data: ");
    scanf("%d %d %d",&a,&b,&c);
    printf("a=%d b=%d c=%d",a,b,c);

    printf(“\nEnter Data: ");  
    scanf("%3d %2d %1d",&a,&b,&c);
    printf("a=%d b=%d c=%d",a,b,c); 	
  }

Enter Data:  123456 8765 887
a=123456 b=8765 c=887
Enter Data:  123456 8765 887
a=123 b=45 c=6