Accessing structure members - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to access the member 'age' of the struct variable 'person'.

C

int age = person.[1];

Drag options to blanks, or click blank then click option'

Aname

Bheight

Cage

Dweight

Attempts:

3 left

💡 Hint

Common Mistakes

Using the arrow operator (->) instead of the dot operator for a struct variable.

Trying to access a member that does not exist in the struct.

The dot operator (.) is used to access members of a struct variable. Here, 'age' is the correct member to access.

2fill in blank

medium

Complete the code to access the member 'salary' of the struct pointer 'empPtr'.

C

float sal = empPtr[1]salary;

Drag options to blanks, or click blank then click option'

A*

B->

C.

D&

Attempts:

3 left

💡 Hint

Common Mistakes

Using the dot operator with a struct pointer.

Dereferencing the pointer manually and then using dot operator incorrectly.

The arrow operator (->) is used to access members of a struct through a pointer.

3fill in blank

hard

Fix the error in accessing the 'id' member from the struct pointer 'studentPtr'.

C

int studentId = studentPtr[1]id;

Drag options to blanks, or click blank then click option'

A.

B&

C*

D->

Attempts:

3 left

💡 Hint

Common Mistakes

Using the dot operator with a pointer.

Trying to dereference the pointer incorrectly.

To access a member of a struct through a pointer, use the arrow operator (->).

4fill in blank

hard

Fill the blank to correctly access the 'grade' member of the struct pointer 'ptr'.

C

char grade = (*ptr)[1]grade;

Drag options to blanks, or click blank then click option'

A.

B*

C->

D&

Attempts:

3 left

💡 Hint

Common Mistakes

Using arrow operator after dereferencing.

Not dereferencing the pointer before using dot operator.

First, dereference the pointer with (*ptr), then use the dot operator (.) to access the member 'grade'.

5fill in blank

hard

Fill the blanks to create a pointer to struct 'Book' and access its 'title' member.

C

struct Book [1]bookPtr = &book;
char* title = bookPtr->title;

Drag options to blanks, or click blank then click option'

A*

B->

C.

D&

Attempts:

3 left

💡 Hint

Common Mistakes

Using dot operator to access members through a pointer.

Not declaring the pointer correctly.

Declare 'bookPtr' as a pointer to struct Book using '*'. Then use the arrow operator (->) to access members through the pointer.

Practice

1. Which operator is used to access members of a structure variable in C?

easy

A. Colon operator (:)

B. Arrow operator (->)

C. Double colon (::)

D. Dot operator (.)

Solution

1. Step 1: Understand structure member access

   In C, when you have a structure variable, you use the dot operator (.) to access its members.

2. Step 2: Differentiate from pointer access

   The arrow operator (->) is used when you have a pointer to a structure, not the structure variable itself.

3. Final Answer:

   Dot operator (.) -> Option D

4. Quick Check:

   Structure variable member access = dot operator (.) [OK]

Hint: Use dot (.) for struct variables, arrow (->) for pointers [OK]

Common Mistakes:

• Confusing dot (.) with arrow (->) operator
• Using colon (:) which is invalid in C
• Using double colon (::) which is from other languages

2. Given the structure struct Point { int x; int y; } p;, which is the correct way to assign 10 to member x?

easy

A. p->x = 10;

B. p:x = 10;

C. p.x = 10;

D. p[x] = 10;

Solution

1. Step 1: Identify the variable type

   Here, p is a structure variable, not a pointer.

2. Step 2: Use correct member access syntax

   For structure variables, use the dot operator (.) to access members, so p.x = 10; is correct.

3. Final Answer:

   p.x = 10; -> Option C

4. Quick Check:

   Structure variable assignment uses dot (.) [OK]

Hint: Use dot (.) for struct variables, arrow (->) only for pointers [OK]

Common Mistakes:

• Using arrow (->) with non-pointer variable
• Using colon (:) which is invalid syntax
• Using array-like syntax on struct members

3. What is the output of this code?

struct Person {
  char name[10];
  int age;
};

int main() {
  struct Person p = {"Amy", 25};
  printf("%s %d", p.name, p.age);
  return 0;
}

medium

A. Amy 25

B. Amy 0

C. Error: cannot assign string to array

D. Random garbage values

Solution

1. Step 1: Understand structure initialization

   The structure p is initialized with "Amy" for name and 25 for age.

2. Step 2: Print structure members

   The printf prints p.name as a string and p.age as an integer, so output is Amy 25.

3. Final Answer:

   Amy 25 -> Option A

4. Quick Check:

   Struct initialized correctly, prints members [OK]

Hint: Initialize structs with braces; access members with dot [OK]

Common Mistakes:

• Thinking string assignment to array is invalid here
• Confusing pointer and array initialization
• Expecting syntax error for string in struct

4. Identify the error in this code snippet:

struct Data {
  int id;
  float value;
};

int main() {
  struct Data d;
  d->id = 5;
  d.value = 3.14;
  return 0;
}

medium

A. Using arrow operator (->) with structure variable

B. Missing semicolon after struct definition

C. Incorrect float assignment

D. No error, code is correct

Solution

1. Step 1: Check member access operators

   The variable d is a structure variable, not a pointer, so d->id is incorrect.

2. Step 2: Correct operator usage

   Use dot operator (.) for structure variables: d.id = 5; is correct.

3. Final Answer:

   Using arrow operator (->) with structure variable -> Option A

4. Quick Check:

   Arrow (->) only for pointers, dot (.) for variables [OK]

Hint: Use dot (.) for struct variables, arrow (->) only for pointers [OK]

Common Mistakes:

• Using arrow (->) on non-pointer struct variable
• Ignoring dot operator for member access
• Assuming no error when mixing operators

5. Consider this code:

struct Employee {
  char name[20];
  int id;
};

int main() {
  struct Employee emp1 = {"John", 101};
  struct Employee *ptr = &emp1;
  ptr->id = 202;
  printf("%s %d", emp1.name, emp1.id);
  return 0;
}

What will be the output?

hard

A. John 101

B. John 202

C. Error: cannot use arrow operator here

D. John 0

Solution

1. Step 1: Understand pointer to structure

   ptr points to emp1, so ptr->id changes emp1.id.

2. Step 2: Update and print values

   After ptr->id = 202;, emp1.id becomes 202. Printing emp1.name and emp1.id outputs John 202.

3. Final Answer:

   John 202 -> Option B

4. Quick Check:

   Pointer access updates struct member correctly [OK]

Hint: Use arrow (->) with pointers to structs to access members [OK]

Common Mistakes:

• Thinking arrow operator causes error with pointers
• Not realizing pointer changes original struct
• Confusing dot and arrow operators with pointers