Where are constant variables stored in C?

In C, constants can be divided into several types, primarily literal constants (Literal Constants) and symbolic constants (Symbolic Constants). The storage location of these constants depends on their type and purpose.

1. Literal Constants: For example, numbers like 123, characters like 'a', and strings like "hello" are typically stored in the program's read-only data segment. This is because the values of literal constants are determined at compile time and remain unchanged during program execution.

2. Symbolic Constants: Constants defined using the #define preprocessor directive or the const keyword. Their storage location may vary slightly:

   • Constants defined with #define: The preprocessor replaces all symbolic constants with their values during preprocessing. Consequently, they do not occupy storage space; instead, they are directly substituted with their values at each usage point.

   • Constants defined with const: These constants are typically stored in the program's data segment, specifically in the read-only data segment or other segments depending on the compiler's implementation. Although variables defined with const are logically not modifiable, the compiler typically allocates storage space to enable access via pointers or similar mechanisms.

For example, consider the following constants defined in a C program:

c
#define PI 3.14159
const int maxScore = 100;

• PI is replaced with 3.14159 at every usage point, consuming no additional memory.

• maxScore may be stored in the read-only data segment, with the exact location depending on how the compiler handles global variables declared with const.

Understanding the storage location of constants aids in better comprehension of memory management and program performance optimization.