Basic Constants & Literals in C Programming

Basic Constants & Literals in C Programming - GATE Computer Science Engineering(CSE) 2023 Mock Test Series - Computer Science Engineering (CSE)

Constants refer to fixed values that the program may not alter during its execution. These fixed values are also called literals.

Constants can be of any of the basic data types like an integer constant, a floating constant, a character constant, or a string literal. There are enumeration constants as well.

Constants are treated just like regular variables except that their values cannot be modified after their definition.

Integer Literals

An integer literal can be a decimal, octal, or hexadecimal constant. A prefix specifies the base or radix: 0x or 0X for hexadecimal, 0 for octal, and nothing for decimal.

An integer literal can also have a suffix that is a combination of U and L, for unsigned and long, respectively. The suffix can be uppercase or lowercase and can be in any order.

Here are some examples of integer literals −

`212         /* Legal */215u        /* Legal */0xFeeL      /* Legal */078         /* Illegal: 8 is not an octal digit */032UU       /* Illegal: cannot repeat a suffix */`

Following are other examples of various types of integer literals −

`85         /* decimal */0213       /* octal */0x4b       /* hexadecimal */30         /* int */30u        /* unsigned int */30l        /* long */30ul       /* unsigned long */`

Floating-point Literals

A floating-point literal has an integer part, a decimal point, a fractional part, and an exponent part. You can represent floating point literals either in decimal form or exponential form.

While representing decimal form, you must include the decimal point, the exponent, or both; and while representing exponential form, you must include the integer part, the fractional part, or both. The signed exponent is introduced by e or E.

Here are some examples of floating-point literals −

`3.14159       /* Legal */314159E-5L    /* Legal */510E          /* Illegal: incomplete exponent */210f          /* Illegal: no decimal or exponent */.e55          /* Illegal: missing integer or fraction */`

Character Constants

Character literals are enclosed in single quotes, e.g., 'x' can be stored in a simple variable of char type.

A character literal can be a plain character (e.g., 'x'), an escape sequence (e.g., ''), or a universal character (e.g., 'u02C0').

There are certain characters in C that represent special meaning when preceded by a backslash for example, newline ( ) or tab ().

Following is the example to show a few escape sequence characters −

`#include <stdio.h>int main() {   printf("Hello	World");   return 0;}`

When the above code is compiled and executed, it produces the following result −

`Hello World`

String Literals

String literals or constants are enclosed in double quotes "". A string contains characters that are similar to character literals: plain characters, escape sequences, and universal characters.

You can break a long line into multiple lines using string literals and separating them using white spaces.

Here are some examples of string literals. All the three forms are identical strings.

`"hello, dear""hello, dear""hello, " "d" "ear"`

Defining Constants

There are two simple ways in C to define constants −

• Using #define preprocessor.

• Using const keyword.

The #define Preprocessor

Given below is the form to use #define preprocessor to define a constant −

`#define identifier value`

The following example explains it in detail −

`#include <stdio.h>#define LENGTH 10   #define WIDTH  5#define NEWLINE ''int main() {   int area;       area = LENGTH * WIDTH;   printf("value of area : %d", area);   printf("%c", NEWLINE);   return 0;}`

When the above code is compiled and executed, it produces the following result −

`value of area : 50`

The const Keyword

You can use const prefix to declare constants with a specific type as follows −

`const type variable = value;`

The following example explains it in detail −

`#include <stdio.h>int main() {   const int  LENGTH = 10;   const int  WIDTH = 5;   const char NEWLINE = '';   int area;        area = LENGTH * WIDTH;   printf("value of area : %d", area);   printf("%c", NEWLINE);   return 0;}`

When the above code is compiled and executed, it produces the following result −

`value of area : 50`

Note that it is a good programming practice to define constants in CAPITALS.

The document Basic Constants & Literals in C Programming | GATE Computer Science Engineering(CSE) 2023 Mock Test Series - Computer Science Engineering (CSE) is a part of the Computer Science Engineering (CSE) Course GATE Computer Science Engineering(CSE) 2023 Mock Test Series.
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FAQs on Basic Constants & Literals in C Programming - GATE Computer Science Engineering(CSE) 2023 Mock Test Series - Computer Science Engineering (CSE)

 1. What are constants and literals in C programming?
Ans. Constants in C programming are fixed values that cannot be changed during the execution of a program. They are also known as literals. Constants can be of different types such as integers, floating-point numbers, characters, and strings. They are used to store values that do not change, such as mathematical constants or fixed values used in calculations.
 2. How are constants represented in C programming?
Ans. Constants in C programming can be represented in different ways. Integer constants can be written as a sequence of digits without any decimal point, while floating-point constants include a decimal point. Character constants are enclosed in single quotes, and string constants are enclosed in double quotes. For example, an integer constant can be written as 10, a floating-point constant as 3.14, a character constant as 'A', and a string constant as "Hello".
 3. What is the difference between a constant and a variable in C programming?
Ans. The main difference between a constant and a variable in C programming is that a constant holds a fixed value that cannot be changed, while a variable can hold different values during the execution of a program. Constants are used to represent fixed values, such as mathematical constants or fixed values used in calculations, while variables are used to store values that can change based on different conditions or inputs.
 4. How are constants defined in C programming?
Ans. Constants in C programming can be defined using the `const` keyword followed by the data type and the constant name. For example, to define an integer constant "PI" with a value of 3.14, we can write `const int PI = 3.14;`. This declaration ensures that the value of "PI" remains constant throughout the program and cannot be modified.
 5. Can constants be modified in C programming?
Ans. No, constants cannot be modified in C programming. Once a constant is defined and assigned a value, its value cannot be changed during the execution of the program. Any attempt to modify the value of a constant will result in a compilation error. Constants are used to represent fixed values that need to remain constant throughout the program.

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