Unit IV: Structures and Unions
Course: Programming with C (SEC)
Code: CASEC101
Basics of Structures and Processing
A structure is a user-defined data type that allows grouping of different data types under a single name. This is essential for representing complex entities like a "student" or "employee".
- Basics of Structures: Defined using the
struct keyword, followed by members of various types.
- Processing: Accessing individual members is done using the dot (.) operator for direct variables.
User Defined Data Types (typedef)
The typedef keyword creates an alias for existing data types, making structure declarations cleaner and easier to read.
Example: typedef struct { int x; int y; } Point; allows using Point p; instead of struct Point p;.
Structures, Pointers, and Functions
Structures can be manipulated using pointers and passed between functions for modular programming.
- Structures and Pointers: When accessing structure members via a pointer, the arrow (->) operator is used.
- Structures and Functions: Structures can be passed to functions by value or by reference (pointer).
- Efficiency: Passing a pointer to a structure is generally more efficient than passing the whole structure by value.
Arrays and Self-referential Structures
- Arrays of Structures: Used to handle multiple records of the same type, such as a list of employee data.
- Pointers to Structures: Pointers can navigate through arrays of structures effectively.
- Self-referential Structures: A structure that contains a pointer to an instance of itself. This is the basis for data structures like Linked Lists.
UNIONS and Table Lookup
Unions provide a way to store different data types in the same memory location.
- UNIONS: Unlike structures, only one member of a union can be stored at any given time. The size of the union is the size of its largest member.
- Table Lookup: Structures and unions are often used to implement lookup tables for efficient data retrieval.
Programming and Problem Solving
Problem-solving in this unit involves using structures and unions to manage real-world data.
- Record Management: Designing programs to handle arrays of records for workers and managers.
- File Export: Printing data from structures into separate files for organized storage.
Exam Focus & Tips
- Exam Tip: Be ready to explain the difference between
struct and union regarding memory.
- Common Mistake: Forgetting the semicolon after the closing brace of a structure definition.
- Mnemonics: "P-A-S-S" - Pointers, Arrays, Structures, Self-referential.
Frequently Asked Questions
Q: What is the primary use of a self-referential structure?
A: They are used to create dynamic data structures such as linked lists and trees.
Q: How do you access a member if you have a pointer to the structure?
A: Use the -> (arrow) operator.