C Tutorial

Tokens in C

In C programming, a token is the smallest unit of a program. Tokens are the building blocks of a C program. A C program is made up of various types of tokens. These include:

🔑 Keywords

Keywords are predefined, reserved words in C that have special meaning. These words cannot be used as identifiers (names of variables, functions, etc.). Examples of keywords include:

int, float, double, char, if, else, while, return, for, break, continue, switch
  

🖊️ Identifiers

Identifiers are the names used to identify variables, functions, arrays, or any other user-defined item. The rules for naming identifiers are:

• 1. An identifier can contain letters (A-Z, a-z), digits (0-9), and underscores (_).
• 2. The first character must be a letter or an underscore.
• 3. Identifiers are case-sensitive (e.g., age and Age are different).

💬 Constants

Constants are fixed values that do not change during the execution of the program. In C, constants can be of various types:

• Integer Constants: Whole numbers, e.g., 10, 100.
• Floating-Point Constants: Numbers with decimal points, e.g., 3.14, 2.718.
• Character Constants: A single character enclosed in single quotes, e.g., 'A', 'b'.

💻 String Literals

String literals are a sequence of characters enclosed in double quotes. For example:

"Hello, World!"
"Welcome to C programming!"
  

➕ Operators

Operators in C are symbols that perform operations on variables and values. There are different types of operators in C, including:

• Arithmetic Operators: +, -, *, /, %
• Relational Operators: ==, !=, >, <, >=, <=
• Logical Operators: &&, ||, !
• Assignment Operator: =

🔍 Separators

Separators are symbols that separate statements and parts of the program. The common separators are:

• Comma (,): Used to separate items in a list.
• Semicolon (;): Used to terminate a statement.
• Parentheses ( () ): Used for grouping or to define a function's parameters.
• Braces ( {} ): Used to define a block of code.

📈 Example: Tokens in a C Program

Here’s an example program with various tokens:

#include    // Header File

int main() {  // Function Start
    int num = 5;   // Keyword, Identifier, Constant
    printf("Value: %d", num);   // Keyword, Identifier, String Literal, Operator
    return 0;   // Keyword, Operator
}
  

📝 Try It Yourself

❌ Common Mistakes

• 🚫 Using a keyword as an identifier (e.g., using int as a variable name).
• 🚫 Forgetting to terminate statements with a semicolon.