C Programming Functions and Pointers

Functions

• Definition: A block of code that performs a specific task, can be reused.
• Syntax:

  return_type function_name(parameter_list) {
      // function body
  }
  

• Types:
  • Standard Library Functions: pre-defined functions like printf(), scanf().
  • User-defined Functions: functions created by the user for specific tasks.
• Return Statement: Ends the function and can return a value to the caller.

Pointers

• Definition: A variable that stores the address of another variable.
• Syntax:
  • Declaration: data_type *pointer_name;
  • Dereferencing: *pointer_name accesses the value at the address.
• Applications:
  • Dynamic memory allocation
  • Array manipulation
  • Function arguments (passing by reference)

Memory Management

• Dynamic Memory Allocation:
  • Functions: malloc(), calloc(), realloc(), free().
• Heap vs. Stack:
  • Heap: Memory allocated during runtime, managed via pointers.
  • Stack: Memory allocated for function calls, automatically managed.
• Best Practices:
  • Always free allocated memory to prevent leaks.
  • Initialize pointers to NULL to avoid dangling pointers.

File I/O

• File Operations:
  • Opening: fopen()
  • Closing: fclose()
  • Reading: fscanf(), fgets(), fread()
  • Writing: fprintf(), fputs(), fwrite()
• File Modes:
  • r: Read
  • w: Write (overwrites existing file)
  • a: Append (adds to the end of file)
  • rb, wb, ab: Binary modes

Data Types

• Basic Data Types:
  • int: Integer type
  • float: Single-precision floating point
  • double: Double-precision floating point
  • char: Character type
• Derived Data Types:
  • Arrays: Collection of elements of the same type.
  • Structures: Custom data types combining different types.
  • Unions: Similar to structures but memory shared among members.

Basic Programs

• Hello World Program:

  #include <stdio.h>
  int main() {
      printf("Hello, World!");
      return 0;
  }
  

• Sum of Two Numbers:

  #include <stdio.h>
  int main() {
      int a, b;
      printf("Enter two numbers: ");
      scanf("%d %d", &a, &b);
      printf("Sum: %d", a + b);
      return 0;
  }
  

IT Companies with Logos

• Microsoft:
  • Logo: Four colored squares (red, green, blue, yellow)
• Apple:
  • Logo: A stylized apple with a bite taken out.
• Google:
  • Logo: Multi-colored (blue, red, yellow, green) lettering.
• IBM:
  • Logo: Blue, striped letters "IBM".
• Amazon:
  • Logo: Text "Amazon" with an arrow from A to Z indicating variety.

Functions

• A function is a reusable block of code designed to perform a specific task.
• Syntax for defining a function includes specifying the return type, function name, and parameter list.
• Standard library functions are pre-defined, such as printf() and scanf().
• User-defined functions are customized to meet specific application needs.
• The return statement concludes the function, optionally returning a value to the caller.

Pointers

• A pointer is a variable that holds the address of another variable.
• Declaration syntax for a pointer includes the data type followed by an asterisk, e.g., data_type *pointer_name;.
• Dereferencing a pointer involves using the asterisk to access the value at the stored address.
• Pointers enable dynamic memory allocation, facilitate array manipulation, and allow function arguments to be passed by reference.

Memory Management

• Dynamic memory allocation functions include malloc() for allocation, calloc() for zero-initialization, realloc() for resizing, and free() for deallocation.
• Memory management distinguishes between heap memory (allocated at runtime and managed manually) and stack memory (allocated automatically for function calls).
• Best practices advocate for freeing allocated memory to prevent memory leaks and initializing pointers to NULL to avoid dangling pointers.

File I/O

• File operations encompass opening files with fopen(), closing them with fclose(), reading contents using fscanf(), fgets(), fread(), and writing with fprintf(), fputs(), fwrite().
• File modes include:
  • r: Opens a file for reading.
  • w: Opens a file for writing, overwriting existing contents.
  • a: Opens a file for appending data to the end.
  • Binary modes are represented as rb, wb, and ab for reading, writing, and appending in binary format, respectively.

Data Types

• Basic data types consist of:
  • int: Represents integer values.
  • float: Represents single-precision floating-point numbers.
  • double: Represents double-precision floating-point numbers.
  • char: Represents a single character.
• Derived data types include:
  • Arrays: Collections of elements of the same data type.
  • Structures: Custom data types that combine different types.
  • Unions: Share memory among different data members, unlike structures.

Basic Programs

• A "Hello World" program demonstrates the simplest usage of printf() for output:

  #include 
  int main() {
      printf("Hello, World!");
      return 0;
  }
  

• A program to calculate the sum of two numbers uses scanf() for input and printf() for output:

  #include 
  int main() {
      int a, b;
      printf("Enter two numbers: ");
      scanf("%d %d", &a, &b);
      printf("Sum: %d", a + b);
      return 0;
  }
  

IT Companies with Logos

• Microsoft: Logo consists of four colored squares in red, green, blue, and yellow.
• Apple: Features a stylized apple with a bite taken out.
• Google: Displays multi-colored lettering (blue, red, yellow, green).
• IBM: Known for its blue, striped letters forming "IBM".
• Amazon: Logo showcases the text "Amazon" with an arrow indicating the range from A to Z.