Pointer Quiz: Master Dynamic Memory Allocation Fundamentals

5 Questions

What is the purpose of the `sizeof` operator in C?

The sizeof operator is used to determine the size (in bytes) of a data type or a variable in C.

Explain the difference between `malloc()` and `calloc()` functions in C.

malloc() allocates a block of memory of the specified size, but the memory is not initialized. calloc() allocates a block of memory and initializes all bits to zero.

How do you access elements within a structure in C?

Elements within a structure are accessed using the dot (.) operator. For example, if person is a structure variable with members name and age, you can access them as person.name and person.age.

What is the purpose of the `fseek()` function in C file handling?

The fseek() function is used to move the file position indicator (cursor) to a specific position within a file.

Explain the concept of an array of pointers in C.

An array of pointers is an array that stores addresses (pointers) instead of values. Each element of the array holds the memory address of a variable or a data structure.

Study Notes

Pointers

Pointer fundamentals: a pointer is a variable that stores the memory address of another variable
Declaring pointer variables: uses an asterisk (*) symbol, e.g. int *ptr
Referencing and de-referencing: & operator gets the memory address of a variable, * operator gets the value stored at a memory address
Pointer arithmetic: allows performing operations on the memory address stored in a pointer

Pointers with Arrays and Strings

Using pointers with arrays: an array name is a pointer to the first element of the array
Using pointers with strings: a string is a character array, and a string literal is a pointer to the first character of the string

Array of Pointers and Pointers as Function Arguments

Array of pointers: an array that stores memory addresses of other variables
Pointers as function arguments: allows functions to modify the original variables passed as arguments
Functions returning pointers: a function can return a memory address, which can be used to access the returned value

Dynamic Memory Allocation

malloc() function: allocates memory of a specified size and returns a pointer to the starting address
calloc() function: allocates memory for an array and initializes it to zero
realloc() function: resizes the memory block allocated by malloc() or calloc()
free() function: releases the memory allocated by malloc(), calloc(), or realloc()
sizeof operator: returns the size of a variable or data type

Structures

Declaring a structure: defines a new data type that can store multiple values of different data types
Reading and assigning structure variables: uses dot notation, e.g. struct_name.member_name
Array of structures: an array that stores multiple structures
Arrays within structures: a structure can have an array as a member
Structures within structures: a structure can have another structure as a member

Comparison with Python

C structures are similar to Python tuples, but C structures can have members of different data types

Unions

Defining and working with unions: similar to structures, but all members share the same memory space

File Handling

Types of files: text files and binary files
File operations: fopen(), fclose(), fgetc(), fputc(), fgets(), fputs(), fscanf(), fprintf(), getw(), putw(), fread(), fwrite(), fseek()
fopen() function: opens a file and returns a file pointer
fclose() function: closes a file
fgetc() and fputc() functions: read and write a single character from/to a file
fgets() and fputs() functions: read and write a string from/to a file
fscanf() and fprintf() functions: read and write formatted data from/to a file
getw() and putw() functions: read and write a word (integer) from/to a file
fread() and fwrite() functions: read and write a block of data from/to a file
fseek() function: moves the file pointer to a specified position in the file