7. Format Specifier, Escape Sequences and Constants in C

 

Format Specifier

Format specifier is a way to tell the compiler what type of data is in a variable during taking input and displaying output to the user. Ex: %c, %d, %f etc.

printf("My phone's battery is %x.yf", var); will print var with y decimal points in x character space.
If the value of x is positive and greater than the character value in var, then extra value of x will be expressed as space before the floating number. If the value of x is negative, then x space bars will be expressed after the floating number.

Escape Sequences in C

An escape sequence in C language is a sequence of characters that doesn't represent itself when used inside string literal or character.
It is composed of two or more characters starting with backslash \. For example : \n represents a new line.

List of Escape Sequences in C

Escape Sequences	Meaning
\a	Alarm or Beep
\b	Backspace
\f	Form Feed
\n	New Line
\r	Carriage Return
\t	Tab(Horizontal)
\v	Vertical Tab
\\	Backslash
\'	Single Quote
\"	Double Quote
\?	Question Mark
\nnn	Octal Number
\xhh	Hexadecimal Number
\0	Null

#include <stdio.h>

int main()
{
   printf("You\nare\nlearning\n\'C\' language\n\"Do you know C language\"");
   return 0;
}

Output :

You
are
learning
'C' language
"Do you know C language"

Constants in C

A constant is a value or variable that can't be changed in the program.
There are different types of constants in C programming.

List of Constants in C

Constant	Example
Decimal Constant	10, 20, 450 etc.
Real or Floating- point Constant	10.3, 20.2, 450.6 etc.
Octal Constant	021, 033, 046 etc.
Hexadecimal Constant	0x2a, 0x7b, 0xaa etc.
Character Constant	'a', 'b', 'x' etc.
String Constant	"c", "c program" etc.

How to define a Constant in C

There are two ways to define constant in C programming.

1. const Keyword

The const keyword is used to define constant in C programming.

#include <stdio.h>

int main()
{
const float PI = 3.14;

printf("The value of PI is : %f\n", PI);
return 0;
}

Output :

The value of PI is : 3.140000

If we try to change the value of PI, it will render compile time error.

2. #define preprocessor

The #define preprocessor is also used to define constant.

#include <stdio.h>
#define PI 3.14

int main()
{
 printf("The value of PI is : %f\n", PI);
 return 0;
}

Output :

The value of PI1 is : 3.140000