Introduction to C Programming

Introduction to C Programming

• C is a broadly used programming language, providing a wide range of functions for various purposes.
• The C standard library offers 15 header files, containing a comprehensive set of functions.
• C has three types of identifiers:
  • Reserved words: predefined words used for specific purposes in the language.
  • Standard identifiers: predefined words in C, often function names from the standard library.
  • Programmer-created identifiers: names chosen by programmers for variables and functions, subject to C's naming rules.
• C is a case-sensitive language, so TOTAL and total are distinct identifiers.

Identifier Rules

• Programmer-created identifiers can be any combination of letters, digits, and underscores (_).
• First character must be a letter or underscore.
• Identifiers cannot be reserved words.
• Blank spaces are not allowed.
• All uppercase letters are used to indicate a constant.
• Function names should be followed by parentheses.
• Descriptive identifiers should be used, like degToRadians(), rather than vague names like easy, duh, or justDoIt.

The main() Function

• The main() function is essential to a C program, often referred to as the driver function.
• The program execution begins at the start of the main() function.
• The end of the main() function marks the end of the program.

Simple Input/Output Operations

• Input refers to any data entered into a program.
• The scanf() function reads formatted input from the standard input, such as keyboards.
• scanf() has the format scanf("%d", &variable);.
• The printf() function is used to format and send data to the standard system display, such as a monitor.
• Passing data to a function is known as passing arguments.
• Messages within printf() are called strings, which are enclosed within double quotes, like "Hello, world!".
• The printf() function has the format printf("Hello there world!");.
• Comments are denoted by / and * symbols and do not affect program execution.

Programming Style: Indentation

• C ignores white space, except for strings, reserved words, and function names.
  • This refers to any combination of spaces, tabs, or new lines.
• Indentation is crucial for readability and organization.
  • Function names are placed on their own lines, with opening and closing braces aligned on their own lines as well.
  • Program statements are indented two spaces within a function.
  • Consistent indentation makes code easier to read and understand.

Programming Style: Comments

• Comments are important for explaining a program's functionality and clarification.
  • They do not impact program execution.
  • Comments can appear anywhere in a program.
  • Comments cannot be nested, so /* invalid */ is not valid.

Common Programming Errors

• Common errors include:
  • Omitting the parentheses after main.
  • Forgetting the opening and closing braces for functions.
  • Misspelling function names, such as print() instead of printf().
  • Neglecting to close strings passed to printf() with double quotes.
  • Omitting semicolons at the end of executable statements.
  • Missing \n to indicate a new line.

Summary

• A C program is composed of one or more functions.
• A function is a C language representation of an algorithm.
• The standard library provides a collection of functions.
  • Programs can utilize functions through the #include directive.