C Programming: Functions

Functions

• A function is a block of code that can be called multiple times from different parts of a program
• Functions can take arguments and return values
• Functions can be classified into:
  • Library functions (e.g. printf, scanf) provided by the C standard library
  • User-defined functions created by the programmer
• Function declaration syntax:

  eturn_type function_name(data_type arg1, data_type arg2, ...);
  

• Function call syntax:

  unction_name(arg1, arg2, ...);
  

Data Structures

• Arrays:
  • A collection of elements of the same data type stored in contiguous memory locations
  • Elements can be accessed using an index (subscript)
  • Array declaration syntax:

    ata_type array_name[size];
    

• Structures:
  • A collection of elements of different data types stored in a single unit
  • Elements can be accessed using the dot (.) operator
  • Structure declaration syntax:

    truct struct_name {
    data_type element1;
    data_type element2;
    ...
    ;
    

Error Handling

• Error handling is the process of detecting and responding to errors or exceptions in a program
• C provides several error handling mechanisms, including:
  • Error codes: returned by functions to indicate errors
  • Error messages: printed to the console to indicate errors
  • Exception handling: using setjmp and longjmp functions to handle exceptions
• Common error handling functions:
  • perror(): prints an error message to the console
  • strerror(): returns a string describing an error code

File Input/Output

• File input/output (I/O) is the process of reading and writing data to files
• C provides several file I/O functions, including:
  • fopen(): opens a file for reading or writing
  • fclose(): closes a file
  • fread(): reads data from a file
  • fwrite(): writes data to a file
  • fscanf(): reads formatted data from a file
  • fprintf(): writes formatted data to a file
• File modes:
  • "r" : read mode
  • "w" : write mode
  • "a" : append mode
  • "r+" : read and write mode
  • "w+" : read and write mode (truncates file if it exists)
  • "a+" : read and append mode

Pointers

• A pointer is a variable that stores the memory address of another variable
• Pointer declaration syntax:

  ata_type *pointer_name;
  

• Pointer operations:
  • Dereferencing: accessing the value stored at the memory address pointed to by a pointer

    pointer_name;
    

  • Address of: obtaining the memory address of a variable

    amp;variable_name;
    

• Pointer arithmetic:
  • Incrementing a pointer: moves the pointer to the next memory location

    ointer_name++;
    

  • Decrementing a pointer: moves the pointer to the previous memory location

    ointer_name--;
    

  • Adding an integer to a pointer: moves the pointer by a certain number of memory locations

    ointer_name += integer;
    

Functions

• A function is a block of code that can be called multiple times from different parts of a program
• Functions can take arguments and return values
• There are two types of functions: library functions (e.g. printf, scanf) and user-defined functions
• The function declaration syntax is: return_type function_name(data_type arg1, data_type arg2,...);
• The function call syntax is: function_name(arg1, arg2,...);

Data Structures

Arrays

• An array is a collection of elements of the same data type stored in contiguous memory locations
• Elements can be accessed using an index (subscript)
• Array declaration syntax is: data_type array_name[size];

Structures

• A structure is a collection of elements of different data types stored in a single unit
• Elements can be accessed using the dot (.) operator
• Structure declaration syntax is: struct struct_name { data_type element1; data_type element2;...};

Error Handling

• Error handling is the process of detecting and responding to errors or exceptions in a program
• C provides several error handling mechanisms, including error codes, error messages, and exception handling
• Error handling functions include perror() and strerror()
• perror() prints an error message to the console
• strerror() returns a string describing an error code

File Input/Output

• File input/output (I/O) is the process of reading and writing data to files
• C provides several file I/O functions, including fopen(), fclose(), fread(), fwrite(), fscanf(), and fprintf()
• File modes include "r" for read mode, "w" for write mode, "a" for append mode, "r+" for read and write mode, "w+" for read and write mode (truncates file if it exists), and "a+" for read and append mode

Pointers

• A pointer is a variable that stores the memory address of another variable
• Pointer declaration syntax is: data_type *pointer_name;
• Pointer operations include dereferencing and obtaining the memory address of a variable
• Dereferencing is done using the asterisk symbol: *pointer_name;
• Obtaining the memory address of a variable is done using the ampersand symbol: &variable_name;
• Pointer arithmetic includes incrementing, decrementing, and adding an integer to a pointer