In C, a token is the smallest element of a program that is meaningful to the compiler.
C programs are made up of tokens combined to form statements and expressions.

The types of tokens in C are:

1. Keywords

2. Identifiers

3. Constants

4. Strings

5. Operators

6. Punctuation (Special Symbols)

1. Keywords

Keywords are reserved words that have a predefined meaning in C.
They cannot be used as identifiers (names of variables, functions, etc.).

Examples of C Keywords

int, float, char, return, if, else, for, while, do, switch, case, break, continue, void, const, static

Example in code

int main() {
    int age = 20;   // 'int' is a keyword
    return 0;       // 'return' is a keyword
}

2. Identifiers

Identifiers are names given to variables, functions, or user-defined items.
They must follow rules:

• Start with a letter or underscore (_)

• Can contain letters, digits, and underscores

• Case-sensitive (age and Age are different)

• Cannot be a keyword

Examples

int studentAge;
float _salary;
char grade;

3. Constants

Constants are fixed values that do not change during program execution.

Types of Constants in C

1. Integer constants → 10, -5, 100

2. Floating-point constants → 3.14, -0.75

3. Character constants → 'A', 'z', '1'

4. String constants → "Hello", "C Programming"

Example

#include <stdio.h>
int main() {
    const int DAYS_IN_WEEK = 7;  // constant integer
    printf("Days in a week = %d", DAYS_IN_WEEK);
    return 0;
}

4. Strings

Strings are sequences of characters enclosed in double quotes " ".

Example

#include <stdio.h>
int main() {
    char name[] = "Denis";    // string literal
    printf("Name: %s", name);
    return 0;
}

• Strings are stored as arrays of characters ending with a null character \0.

5. Operators

Operators are symbols that perform operations on variables and values.

Types of Operators

Example

#include <stdio.h>
int main() {
    int a = 10, b = 5;
    int sum = a + b;      // Arithmetic operator +
    int isEqual = (a == b); // Relational operator ==
    int result = (a > b) ? a : b;  // Conditional operator ?
    printf("Sum = %d, Is Equal = %d, Result = %d", sum, isEqual, result);
    return 0;
}

6. Punctuation (Special Symbols)

Punctuation symbols are used to separate statements or group code in C.

Common Punctuation Symbols in C

Example

#include <stdio.h>
int main() {
    int numbers[5] = {1, 2, 3, 4, 5};  // { } used for block/array, ; ends statements
    printf("First number = %d", numbers[0]); // [ ] used to access array
    return 0;  // ; ends statement
}

✅ Summary

Tokens are the building blocks of a C program.
They include:

• Keywords: Reserved words

• Identifiers: Names of variables, functions

• Constants: Fixed values

• Strings: Sequences of characters

• Operators: Perform operations

• Punctuation: Special symbols to structure code

All C programs are built using these fundamental elements.