Javatpoint Logo
Javatpoint Logo

Symbolic Constants in C

Identifiers are used to represent fixed values in programs using symbolic constants in the C programming language. These parameters are frequently used to increase the readability, maintainability, and modifiability of code, which may be numerical or not. The C language's "#define" command is used to declare symbolic constants.


Syntax for defining a symbolic constant in C:

In this example, the symbolic constant "MAX_V" is specified to have a value of 100. It indicates that the number 100 will be substituted for "MAX_V" wherever it appears in the code at compilation time.

We may specify non-numerical values like strings using symbolic constants.

For example:

In this example, the text "INVALID" is declared as the symbolic constant "error". It can be helpful for defining error messages or other strings that are frequently used throughout a program.

Additionally, macros, which are essentially functions that are expanded at compile time, can be defined using symbolic constants.

For example:

In this example, the macro "CUBE" is defined to accept a single input "x" and return the cube of that argument. It can be helpful for defining additional little functions that are regularly utilized throughout a program or for carrying out simple computations.

Some other information about these symbolic constants in C is as follows:

  • Scope: Symbolic constants that are declared with the "#define" directive have global scope, allowing for usage throughout the whole program. It may work to your favor or disadvantage depending on the circumstances. On the one hand, it implies that the symbolic constant must only be defined once before being used across the entire program. On the other hand, it implies that other program elements may unintentionally change or redefine the symbolic constant, which might result in errors and unexpected behavior.
  • Naming Conventions: Typically, underscores are used to separate words in the names of symbolic constants, which are written in all capital letters. It serves to emphasize their constant, unchanging character and makes them simpler to differentiate from other program identifiers.
  • Advantages: The use of symbolic constants in C has several advantages. They may start by making the code easier to read by assigning fixed value names that make sense. It can make the code simpler to comprehend for other programmers and easier to maintain and alter in the future. They can also increase the code's adaptability by enabling simple changes to fixed values in a single location. By doing so, the code can become more modular and assist in preventing errors. Allowing the compiler to optimize the code at compile time rather than during runtime can also increase the code's efficiency.
  • Preprocessor: The C preprocessor contains the "#define" command that is a distinct program that runs before the compiler. The preprocessor oversees carrying out certain tasks, such as file inclusion, conditional compilation, and macro expansion. Before the compiler runs, the preprocessor replaces all instances of a symbolic constant with its defined value in the case of such constants.
  • Type-Safety: Because they lack an inherent data type, symbolic constants in C are not type-safe. When a symbolic constant is used in an expression, the C preprocessor just replaces the identifier with the constant's value. If the value's type is incompatible with the remainder of the expression, it might result in unexpected behavior. It's a good idea to create symbolic constants for values of a certain type and apply them consistently across the program to reduce this danger.
  • Alternatives: C offers Enums and const variables as additional means of defining fixed values in addition to symbolic constants. While const variables are used to define constants with a specific data type, Enums are used to define a collection of related constants. Const variables and Enums are both type-safe, allowing the compiler to detect type issues at build time.
  • Macro vs constant: Symbolic constants in C can be defined using either a "const" declaration or the "#define" directive. There are several significant variations between the two techniques, even though they both specify a fixed number that may be utilized throughout the program. While "const" variables are handled by the compiler and kept in memory, macros defined using "#define" are processed by the preprocessor and replaced with their values at compile time. While macros are not type-safe, "const" variables are. The decision between macros and const variables relies on the particular program needs.
  • Performance: Using symbolic constants in C has the benefit of enhancing performance by enabling the compiler to carry out optimizations at the time of compilation. For instance, the compiler may replace all instances of a symbolic constant with its value at build time rather than having to search up the value at runtime if the constant value is used repeatedly throughout the program.
  • Macros: With the help of C's robust macro functionality, you may construct complex code structures that can be extended at compilation time. One kind of macro is one that creates symbolic constants using the "#define" Macros can be used to define functions, control structures, and other intricate code structures in addition to symbolic constants.
  • In addition to the ability to establish straightforward symbolic constants using the "#define" directive, C also offers sophisticated methods for specifying complicated constant values. For instance, you may construct a group of related constants using the "enum" keyword, or you can define constants with particular data types using "const" Additionally, C offers a number of built-in constants that are frequently used in C programs, including "NULL" and "EOF".
  • Compatibility: The majority of C compilers and programming environments support symbolic constants. However, some older compilers might only partially support the C preprocessor or might have restrictions on the number or size of defined symbolic constants.

Youtube For Videos Join Our Youtube Channel: Join Now


Help Others, Please Share

facebook twitter pinterest

Learn Latest Tutorials


Trending Technologies

B.Tech / MCA