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Structures
Description: A structure is a user-defined data type that groups related variables of different data types into a single unit. Structures are used to represent a record or a complex data type, allowing the combination of various data types under one name.
Key Components:
- Structure Declaration: The definition of the structure that specifies its name and the types of its members (fields).
- Members: Variables of different types contained within the structure. Each member can be accessed using the structure variable.
- Structure Variable: An instance of a structure that holds the actual data.
Features:
- Heterogeneous Data Types: Structures can contain members of different data types (e.g., integers, floats, characters).
- Data Encapsulation: Structures encapsulate related data, providing a way to represent a complex entity.
- Memory Allocation: Memory for the entire structure is allocated as a single block, which is contiguous in memory. The total size is the sum of the sizes of its members (with possible padding).
- Accessing Members: Members of a structure can be accessed using the dot operator (
.) for structure variables or the arrow operator (->) for pointers to structures. - Pass by Value/Reference: Structures can be passed to functions either by value (copying the entire structure) or by reference (passing a pointer to the structure), allowing for different memory management strategies.
Unions
Description: A union is a user-defined data type that allows storing different data types in the same memory location. Unlike structures, all members of a union share the same memory space, meaning only one member can hold a value at any given time.
Key Components:
- Union Declaration: The definition of the union that specifies its name and the types of its members.
- Members: Variables of different types contained within the union. All members share the same memory location.
- Union Variable: An instance of a union that holds the actual data.
Features:
- Memory Efficiency: Unions save memory since all members share the same memory space. The size of the union is determined by the size of its largest member.
- Homogeneous Access: While unions can store different data types, only one member can contain a valid value at a time. Care must be taken to manage which member is currently valid.
- Accessing Members: Members of a union can be accessed using the dot operator (
.) for union variables or the arrow operator (->) for pointers to unions. - Type Safety: Unions can introduce complexity and risk of data corruption if not managed correctly. Users must ensure they access the correct member that has been assigned a value.
- Use Cases: Unions are commonly used in applications where different data types might be needed, such as implementing variant types, handling different formats in the same data structure, or working with low-level data management.