Formatted console i/o functions

Formatted console i/o functions

Functions printf() and scanf() are come under the formatted console i/o functions. These functions allow us to input read from the keyboard or the output display on the screen in a formatted way as per our requirements

We can control how many floating points are there in output, how many spaces would be present between the two values, even we can decide where the space should be on the left side or right side and the number of places after the decimal points using formatted functions.

Let us discuss these functions one by one first of all we have gone to talk about the printf() function, we have habituated to use of it. but without the introduction of it formally.

The general form of printf() looks like

printf("control string", list of variables);

The control string can contain three things.

Characters that printed (on-screen) without any change.

Escape sequences which start from character backslash \ sign

Conversion or format specifications that begin with % sign followed by format specifier.

For example

#include<stdio.h>

int main() {

int num1, num2, total;

num1=12;

num2=10;

total=num1 + num2;

printf("This program does total of two numbers \n");

printf("number are %d and %d \n",num1,num2);

printf("Total is %d", total);

return 0;

}

Output

This program does a total of two numbers

number are 12 and 10

Total is 22

Now in the above program when the first printf is executed it printed all characters on screen without any change. When it met escape sequence it takes appropriate action in our case it is '\n' when it met it the cursor is beginning of the new line

In second print executed it prints the characters when the format specifier met it picked up the value from variables by their order that we specified on the right side of the string as arguments.

Now in c the functions calling convention is from right to left as we know the printf() is the function so the value of format specifies are comes from the right to left, in our example first num2's value is placed on the string then the value of num1. we use %d as format specifies in the string because the variable type is integer.

Now you can understand the third printf in your program.

Escape sequences

In c programming language, there are 256 numbers of character in character set they mainly divided into 2 parts

ASCII characters set

Extended ASCII characters set.

Apart from that, some other characters are also there which are not part of any character set, they known as Escape characters

We saw that the newline character \n in formatting string takes the cursor to the beginning of the next line. Here "\" symbol is considered as escape character so-called them Escape sequences

Examples of escape sequences

\n	Newline
\t	Tab (Horizontal)
\b	Backspace
\a	alert (Beep)
\v	vertical tab
\'	Single quote
\"	Double quote
\\	backslash
\f	Form feed,

\t moves the cursor to the next tab stop.

\r moves the cursor to the beginning of the line in which it is currently placed.

\a alerts the user by sounding the speakers.

\b moves the cursor one position to the left of its current position.

\f (form feed) advances the computer stationery attached to the printer to the top of the next page

Example

#include<stdio.h>

int main()

{

print("here we go! 3\a 2\a 1\a");

printf("\n This is escape sequences");

printf("\n \" back\bspace\" ");

return 0;

}

Output:

here we go! 3 2 1

This is escape sequences

"backspace"

Format specifications

the %d we used earlier to print total and num1 and num2 here %d is called as format specifiers, Followings are format specifiers that can be used with the printf() function.

	Datatype	Format specifies
Char	charsigned char unsigned char	%c%c %c
Integer	short intunsigned short int unsigned int int long int long long int unsigned long int unsigned long long int	%hd%hu %u %d %ld %lld %lu %llu
Real	floatdouble long double	%f%lf %Lf
String		%s

Specifiers in format specifications

Printing integer number:

As we know %d is used as format specifier for print integer number

Now to print integer in formatted way we use %wd

Where w denotes the with of the field in number of character for example %4d is print the variable as a decimal integer in a field of 4 columns. if the value to be printed is not fill up all entire field then the value is align to right and the best blanks fields are padded on the left side.

Now if we assign a minus (-) sign to the format specifier then if the value to be printed is not fill up all entire field then the value align to left and rest blank space align to right.

Example:

#include<stdio.h>

int main()

{

int n=1234;