CS101 Lecture 6: Working with Pointers

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Questions and Answers

What is a pointer in C referred to as?

Locator or indicator (correct)

Value holder

Memory block

Reference variable

What does the expression *p represent when p is a pointer?

The value stored at the address p points to (correct)

The data type of p

The size of p in memory

The address of p

Which operator is used to obtain the address of a variable in C?

| (reference operator)

& (address-of operator) (correct)

# (memory address operator)

* (dereference operator)

What is a result of initializing a pointer with a variable of a different data type?

It results in a type mismatch error Signup and view all the answers

What benefit do pointers provide in handling arrays and structures?

Improves performance and efficiency Signup and view all the answers

Which of the following correctly declares a pointer to an integer?

int *ptr; Signup and view all the answers

In the context of pointers, what is the role of the dereference operator (*)?

To access the value at the address the pointer points to Signup and view all the answers

What is a primary use of pointers related to functions?

They can pass functions as arguments Signup and view all the answers

What does the dereference operator (*) do in C?

It retrieves the value from a variable's address. Signup and view all the answers

What is the correct way to assign a pointer the address of a variable in C?

p = &a; Signup and view all the answers

What will the statement `printf("The address of a is:%p", p);` output if p points to variable a?

The address of variable a. Signup and view all the answers

Which format specifier is used to print an unsigned integer in hexadecimal notation in C?

%x Signup and view all the answers

What does it mean if a pointer is assigned the value NULL?

The pointer is pointing to nothing. Signup and view all the answers

Which of the following statements correctly describes the relationship between a variable and a pointer?

A pointer stores the address of the variable. Signup and view all the answers

What is the output of `printf("The value of a is:%d", *p);` if a is 10?

10, since p dereferences to the value of a. Signup and view all the answers

Which of the following best describes the purpose of the & operator in C?

It gets the address of a variable. Signup and view all the answers

What is the base address of the array arr if it starts at address 1000 and each integer requires two bytes?

1000 Signup and view all the answers

What happens when you attempt to execute p-- after incrementing the pointer p?

It will cause an error. Signup and view all the answers

What is the C language statement that effectively initializes the pointer p to the base address of the array arr?

p = &arr; Signup and view all the answers

Which of the following statements regarding pointer arithmetic with arrays is true?

Incrementing a pointer moves it to the next element in the array. Signup and view all the answers

In the context of pointers, what is the difference between using p = arr; and p = &arr;?

They are equivalent and will have the same effect. Signup and view all the answers

What is the correct way to declare a pointer that points to the integer variable Number?

int *point = &Number; Signup and view all the answers

Which function is used to print the address of the variable Number?

printf('The address is: %p', &Number); Signup and view all the answers

What will be the value of Number after incrementing it by 10 using the pointer point?

52 Signup and view all the answers

What does the pointer 'ptr' refer to after the statement 'ptr = &q;'?

The address of q Signup and view all the answers

Which statement correctly prints the value of Number using the pointer variable point?

printf('Value of number: %d', *point); Signup and view all the answers

In the statement 'printf("%d", ptr);', what does 'ptr' output?

The value of q Signup and view all the answers

What will be the result of dividing two integers where the second integer is zero?

An error occurs Signup and view all the answers

What is the output of 'printf("%p \n", p);' if 'p' is a pointer to 'var'?

Address of var Signup and view all the answers

How can you find the maximum of two numbers using pointers in C?

By dereferencing the pointers and using an if statement. Signup and view all the answers

What is the purpose of the statement 'p = &var;' in the given C program?

To make p point to the address of var Signup and view all the answers

How would the output differ if 'printf("%u", *p);' is executed?

It shows the value of 'var' Signup and view all the answers

What is the expected output if the two input numbers are 10 and 20 during arithmetic operations?

Sum = 30, Difference = -10, Product = 200, Quotient = 0 Signup and view all the answers

Given 'int var = 10;', which statement correctly retrieves the value of 'var' using its pointer?

printf("%d", *p); Signup and view all the answers

What happens to the memory allocated for an array when it is declared in C?

It remains allocated for the duration of the program. Signup and view all the answers

What does the '%u' format specifier in printf expect as an argument?

An unsigned integer Signup and view all the answers

What would happen if 'p' were declared as 'int p;' instead of 'int *p;'?

It would cause a compilation error Signup and view all the answers

What is the expected output when calling 'printf("%p", &p);'?

The address of pointer p Signup and view all the answers

Study Notes

CS101 Introduction to Programming

Course name: CS101 Introduction to Programming
Institution: MedTech, Mediterranean Institute of Technology
Date: 12/02/2024

Lecture 6: Working with Pointers

Topic: Working with pointers
Lecture number: 6

Outlines

Topic: Pointers
Topic: Pointers for Inter-Function Communication

Pointers

Definition: A pointer is a variable that stores/holds the address of another variable of the same data type. It is also known as a locator or indicator that points to an address of a value.
Data type: A pointer is a derived data type in C.
Benefits:
- More efficient in handling arrays and structures.
- Allows references to functions and helps in passing functions as arguments to other functions.
- Reduces program execution time.
- Enables dynamic memory management in C.

Pointers: Declaration Vs Initialization

Declaration: data_type *pointer_variable_name; (e.g., int *p;)
Dereference operator: The * operator is used to access the value stored at the memory address. If a pointer p stores the address of a variable, *p gives the value in that location.

Pointers: Initialization of Pointer Variable

Initialization: Assigning an address of a variable to a pointer variable.
Example: int *ptr = &a, where a is the variable.

Pointers: Example

Addresses and values illustration: The pointer variable stores the address, and the dereference operator accesses the value.

Pointers: Summary

Reference operator (&): Retrieves the address of a variable.
Dereference operator (*): Accesses the value at the specified address.

Pointers: Dereferencing

Accessing a variable's value using a pointer: The dereference operator is used to access data at an address pointed to by a pointer.

Pointers: Practice

Program example for basic pointer operations: A C program is provided to demonstrate basic pointer operations.

Pointers: Solution

Solution to the practice: The solution to the given C program in the practice question is provided. Output is shown.

Pointers: Examples 1 and 2

Programs illustrating pointer concepts: Examples in C programs demonstrate various aspects of pointer usage.

Pointers: Exercises and Answers

Practice problems and solutions: Example problems regarding pointer usage in C. Answers included for the provided exercises.

Pointers for Inter-Function Communication

Arrays and Pointers: An array's name directly refers to the address of the first element.
Pointer to an array: A pointer can be used to point to an array.

Pointers to Arrays

Accessing array elements through pointers: Explain how to traverse and access array elements using pointer arithmetic and the array name.

Relation between Arrays and Pointers

Array name represents the base address: The array name in C acts as a pointer to the first element.

Pointers for Inter-Function Communication: Example 1 and 2

Detailed array-pointer examples: Demonstrates array pointer usage in a C program..

Pointers to Void

Void pointers: Explanation of void pointers; they can hold memory addresses of any type and are generally used for flexibility in function arguments

Pointers to Pointers

Definition: A pointer variable can hold the address of another pointer.
Example programs and concepts: Example programs demonstrating pointer to pointers in C using variables.

Memory Allocation Functions

Dynamic memory allocation: The use of malloc() and calloc() to allocate memory during program execution, emphasizing when each is appropriate.

Difference between static and dynamic memory allocation

Difference between static and dynamic allocation: Discusses the runtime vs compile-time nature of memory allocation.

Difference between malloc() and calloc()

malloc() vs calloc() function: Differences in behavior and use of these memory allocation techniques.

Review

Summary of key programming tasks involving pointers.

Pointers (Extra)

Additional practice problems (examples): Explanation and solution to pointer-based practice problems relevant to the content.

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Description

This quiz covers Lecture 6 of CS101 Introduction to Programming, focusing on pointers in C. Understand the definition, benefits, and the difference between declaration and initialization of pointers. Test your knowledge on how pointers facilitate inter-function communication and memory management.