Pointers in C Programming

Pointers

• A pointer is a variable that stores the memory address of another variable.
• Declared using the asterisk symbol (*) before the pointer name.
• Can be used to dynamically allocate memory using malloc() and free() functions.
• Pointer arithmetic:
  • Incrementing a pointer (ptr++) moves it to the next memory location.
  • Decrementing a pointer (ptr--) moves it to the previous memory location.
  • Adding an integer to a pointer (ptr + n) moves it to the nth next memory location.
• Pointer types:
  • void* : generic pointer that can point to any data type.
  • char* : pointer to a character.
  • int* : pointer to an integer.

Functions

• A function is a block of code that can be called multiple times from different parts of a program.
• Declared using the return-type function-name(parameters) syntax.
• Function types:
  • void : function that does not return a value.
  • int : function that returns an integer.
  • char* : function that returns a string.
• Function arguments:
  • Passed by value: a copy of the variable is passed to the function.
  • Passed by reference: a pointer to the variable is passed to the function.
• Function recursion: a function that calls itself repeatedly until a base case is reached.

Data Structures

• Arrays:
  • Declared using the type name[size] syntax.
  • Elements are stored in contiguous memory locations.
  • Can be initialized using the type name[] = {values} syntax.
• Structures:
  • Declared using the struct name { members } syntax.
  • Members are variables of different data types.
  • Can be used to create complex data structures.
• Linked Lists:
  • A dynamic collection of nodes, each pointing to the next node.
  • Each node contains a value and a pointer to the next node.
  • Can be used to implement stacks, queues, and other data structures.

Error Handling

• Error types:
  • Compile-time errors: caught by the compiler during compilation.
  • Runtime errors: caught during program execution.
  • Logical errors: incorrect program logic.
• Error handling techniques:
  • Using if statements to check for error conditions.
  • Using assert statements to check for error conditions.
  • Using try-catch blocks to handle exceptions.
• Error handling functions:
  • errno : a global variable that stores the error code.
  • perror : a function that prints the error message.

File Input/Output

• File modes:
  • r : read mode.
  • w : write mode.
  • a : append mode.
  • r+ : read and write mode.
• File functions:
  • fopen : opens a file and returns a file pointer.
  • fclose : closes a file.
  • fread : reads data from a file.
  • fwrite : writes data to a file.
  • fseek : moves the file pointer to a specific location.
  • ftell : returns the current file pointer location.
  • rewind : moves the file pointer to the beginning of the file.

Pointers

• A pointer is a variable that stores the memory address of another variable, declared using the asterisk symbol (*).
• Pointers can be used to dynamically allocate memory using malloc() and free() functions.
• Pointer arithmetic is possible, and it includes incrementing, decrementing, and adding an integer to a pointer.

Functions

• A function is a block of code that can be called multiple times from different parts of a program, declared using the return-type function-name(parameters) syntax.
• Functions can return different data types, such as void, int, and char*.
• Function arguments can be passed by value or by reference.
• Function recursion is a technique where a function calls itself repeatedly until a base case is reached.

Data Structures

• Arrays are declared using the type name[size] syntax and elements are stored in contiguous memory locations.
• Arrays can be initialized using the type name[] = {values} syntax.
• Structures are declared using the struct name { members } syntax and can be used to create complex data structures.
• Linked Lists are a dynamic collection of nodes, each pointing to the next node, and can be used to implement stacks, queues, and other data structures.

Error Handling

• Error types include compile-time errors, runtime errors, and logical errors.
• Error handling techniques include using if statements, assert statements, and try-catch blocks.
• Error handling functions include errno, which stores the error code, and perror, which prints the error message.

File Input/Output

• File modes include r for read mode, w for write mode, a for append mode, and r+ for read and write mode.
• File functions include fopen, which opens a file and returns a file pointer, fclose, which closes a file, fread, which reads data from a file, and fwrite, which writes data to a file.
• Other file functions include fseek, which moves the file pointer to a specific location, ftell, which returns the current file pointer location, and rewind, which moves the file pointer to the beginning of the file.