Tokens in C

The C programming, a token is the smallest unit in a program. Tokens are the building blocks of a C program and are recognized by the C compiler. There are several types of tokens in C:

1. Keywords:

• Keywords are reserved words that have a specific meaning in the C language.
• Examples: int, if, while, for, return, char, double, struct, break, continue, etc.

1. Identifiers:

• Identifiers are used to name various program elements such as variables, functions, arrays, and more.
• An identifier is a sequence of letters, digits, and underscores that must begin with a letter or underscore.
• Examples: main, counter, my_function, MAX_SIZE, totalAmount, etc.

1. Constants:

• Constants represent fixed values that do not change during program execution.
• Types of constants include integer constants (e.g., 42), floating-point constants (e.g., 3.14), character constants (e.g., 'A'), and string literals (e.g., "Hello, World!").

1. String Literals:

• String literals are sequences of characters enclosed in double quotes.
• Example: "Hello, World!"

1. Operators:

• Operators perform operations on operands to produce a result.
• Examples: +, -, *, /, %, =, ==, !=, <, >, <=, >=, &&, ||, &, |, !, ++, --, etc.

1. Punctuation Symbols:

• Punctuation symbols include characters like parentheses (), braces {}, square brackets [], commas ,, semicolons ;, periods ., arrow ->, etc.
• These symbols are used for grouping, separating, and terminating statements and expressions.

1. Preprocessor Directives:

• Preprocessor directives are commands to the C preprocessor and start with #.
• Examples: #include, #define, #ifdef, #endif, #ifdef, #pragma, etc.

1. Comments:

• Comments are not considered tokens by the compiler but are essential for code documentation.
• Single-line comments start with //, and multi-line comments are enclosed in /* */.

Here’s an example illustrating various types of tokens in a simple C program:

#include <stdio.h>

// Function prototype
int add(int a, int b);

int main() {
    int num1 = 10; // Identifier: num1, Constants: 10
    int num2 = 20; // Identifier: num2, Constants: 20
    int sum = add(num1, num2); // Identifier: sum, Function: add
    printf("The sum is %d\n", sum); // Identifiers: printf, "The sum is %d\n"

    return 0;
}

// Function definition
int add(int a, int b) {
    return a + b;
}

In this example, you can see various types of tokens, including keywords (int, return), identifiers (main, num1, add), constants (10, 20), operators (=, +), punctuation symbols (;, {, }), preprocessor directives (#include, #define), and comments (// Function prototype, /* Function definition */). These tokens collectively make up the C program’s syntax and semantics.