C_07 Constants in C | Types of Constants | Programming in C

Summary

This video introduces constants in C programming, detailing their fixed values that remain unchanged during execution. Constants are classified into numeric (including integer and floating-point) and character types. The video explains how to declare constants using the `const` keyword and `#define` directive, highlighting the importance of naming conventions and syntax rules. Viewers will learn about valid and invalid constant examples, as well as the differences between character constants and string constants. The session sets the foundation for further programming concepts, particularly focusing on constants as a precursor to variables in C.

Takeaways

• 😀 Constants in C are fixed values that cannot change during program execution.
• 😀 There are two main types of constants: numeric constants and character constants.
• 😀 Numeric constants can be further divided into integer constants and real (floating-point) constants.
• 😀 Integer constants can be expressed in decimal, octal, or hexadecimal formats.
• 😀 Real constants contain a decimal point and can also be represented in exponential form.
• 😀 Character constants are single characters enclosed in single quotes, while string constants are enclosed in double quotes.
• 😀 To declare symbolic constants, use the `#define` directive, and for constant variables, use the `const` keyword.
• 😀 Rules for integer constants include no spaces or special characters between digits.
• 😀 The value of a constant defined with `const` cannot be changed after initialization.
• 😀 Understanding constants is crucial for writing effective and error-free C programs.

Q & A

What are constants in C language?

Constants in C are fixed values that do not change during the execution of a program. They are specified by the programmer and known to the compiler at compile time.

What is the difference between symbolic constants and numeric constants?

Symbolic constants are defined using the `#define` preprocessor directive, allowing for fixed values to be given a name (e.g., `#define PI 3.14`). Numeric constants, on the other hand, are actual fixed values used in the code, such as `10` or `3.14`.

How are integer constants categorized in C?

Integer constants are categorized into three types: decimal constants (base 10), octal constants (base 8, starting with 0), and hexadecimal constants (base 16, starting with 0x).

What is a real constant in C?

Real constants, also known as floating-point constants, include decimal values that contain a fractional part, such as `12.56` or can be expressed in exponential form like `1.23e4`.

What are character constants in C?

Character constants are single characters enclosed within single quotation marks, such as 'a' or '1'. They can also include escape sequences, like '\n' for a newline.

What distinguishes a string constant from a character constant?

A string constant is a sequence of characters enclosed in double quotation marks, while a character constant is a single character in single quotation marks. For example, 'a' is a character constant, while "abc" is a string constant.

How do you declare a constant in C?

You can declare a constant using the `const` keyword, such as `const int a = 10;`, or by using `#define`, like `#define MAX 100`. The former creates a read-only variable, while the latter defines a symbolic constant.

What rules must be followed when using `#define` for constants?

When using `#define`, there should be no space between `#` and `define`, and there should be a space between `define` and the name of the constant. Also, avoid using semicolons and equal signs in the definition.

What happens if you attempt to change the value of a constant declared with `const`?

If you try to change the value of a constant declared with `const`, the compiler will produce an error, indicating that the value is read-only and cannot be modified.

Can arithmetic operations be performed on character constants?

Yes, arithmetic operations can be performed on character constants because each character has an associated ASCII value. For instance, if you print the integer value of 'A', it will output 65.