Quant Formula Sheet

What is a Structure?

A structure (struct) is a user-defined data type that groups variables of different data types under one name.

Unlike arrays, which store elements of the same type, structures can store heterogeneous data.

struct Student {
    int roll;
    char name[20];
    float marks;
};

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Declaring and Initializing Structures

struct Student s1 = {1, "Amit", 92.5};

printf("%d\n", s1.roll);
printf("%s\n", s1.name);
printf("%.1f\n", s1.marks);

Output

1
Amit
92.5

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Accessing Structure Members

Use the dot (.) operator for structure variables.

struct Student s;

s.roll = 10;
printf("%d", s.roll);

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Structure Pointer

Use the arrow (->) operator with pointers.

struct Student s = {1, "Amit", 90};

struct Student *ptr = &s;

printf("%s", ptr->name);

ptr->name is equivalent to (*ptr).name.

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Array of Structures

Each array element is a complete structure.

struct Student s[2] = {
    {1, "Amit", 90},
    {2, "Rahul", 95}
};

printf("%s", s[1].name);

Output

Rahul

---

Nested Structures

A structure can contain another structure.

struct Date {
    int day;
    int month;
    int year;
};

struct Student {
    char name[20];
    struct Date dob;
};

struct Student s = {"Amit", {10, 5, 2002}};

printf("%d", s.dob.year);

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typedef with Structures

typedef removes the need to write struct every time.

typedef struct {
    int roll;
    char name[20];
} Student;

Student s1;

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Self-Referential Structure

Used in linked lists and trees.

struct Node {
    int data;
    struct Node *next;
};

A structure cannot contain an object of its own type directly, but it can contain a pointer to its own type.

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Passing Structures to Functions

struct Student {
    int roll;
};

void print(struct Student s)
{
    printf("%d", s.roll);
}

Structures are passed by value unless a pointer is used.

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Structure Padding

Compilers may insert unused bytes between members for memory alignment.

struct Demo {
    char c;
    int x;
};

Even though the members occupy 5 bytes, sizeof(struct Demo) is often 8 bytes because of padding.

This is one of the most common CDAC C-CAT questions.

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Structure vs Union

Structure	Union
Each member has separate memory	All members share the same memory
All members can store values simultaneously	Only one member is meaningful at a time
Size is approximately sum of member sizes (plus padding)	Size equals the largest member

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Common CDAC C-CAT MCQs

Q1

Which operator is used to access members using a structure pointer?

A) . B) -> C) & D) ::

Answer: B

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Q2

struct Point {
    int x;
    int y;
};

struct Point p = {10, 20};

printf("%d", p.y);

A) 10

B) 20

C) Garbage

D) Error

Answer: B

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Q3

Which statement is true?

A) Structures can contain different data types.

B) All members share the same memory.

C) Structures cannot be passed to functions.

D) Structures cannot contain arrays.

Answer: A

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Q4

Which operator is equivalent to ptr->roll?

A) *ptr.roll

B) (*ptr).roll

C) ptr.roll

D) &ptr.roll

Answer: B

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Q5

Which structure is valid?

A)
struct Node{
    int data;
    struct Node next;
};

B)
struct Node{
    int data;
    struct Node *next;
};

A) Only A

B) Only B

C) Both

D) Neither

Answer: B

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CDAC C-CAT Tips

• Remember the difference between . and ->.
• Learn how typedef struct simplifies declarations.
• Expect questions on structure padding and sizeof().
• Self-referential structures are heavily used in linked lists and trees.
• Know the difference between structures and unions.

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Key Takeaways

• Structures group heterogeneous data into a single user-defined type.
• Use . with structure variables and -> with structure pointers.
• Arrays of structures store multiple records efficiently.
• Structures can be nested and passed to functions.
• Padding may increase the size returned by sizeof(struct).
• typedef makes structure declarations cleaner.
• Structures allocate separate memory for each member, unlike unions.