Unwrapping the mystery of * in C programming

Most of the beginners to the C programming language struggle with the symbol *. We are here to learn about this notation in a very simple way.

The symbol * is used mainly in three places:

1. In an arithmetics expression

2. During the declaration of a pointer variable

3. In the expressions involving pointer variables.

Hence, there are three names for this symbol in C:

1. Multiplication Operator

If the symbol * is used in arithmetic expressions (between two normal variables ), we call it a Multiplication Operator.

Here is a simple code example:

int main() {
    int a,b,c;
    a = 10;
    b = 5;
    c = a*b;  // Here * is a Multiplication operator
    printf("value of c = %d",c);
    return 0;
}

Output:

value of c = 50

2. Indirection Operator

If the symbol * is used during the declaration of a pointer variable then we call it an Indirection Operator. The symbol * directs the compiler during lexical analysis phase that the variable name after this is for a pointer variable, not for a normal variable.

int main() {
    int a,b,c;
    int *p;  // Here * is an Indirection operator
    p = &c;
    a = 10;
    b = 5;
    c = a*b;  // Here * is a Multiplication operator
    printf("value of c = %d",c);
    return 0;
}

Output:

value of c = 50

3. Value at Operator

If the symbol * is used in the expressions before pointer variables then we call it a Value at Operator.

int main() {
    int a,b,c;
    int *p;  // Here * is an Indirection operator
    p = &c;
    a = 10;
    b = 5;
    c = a*b;  // Here * is a Multiplication operator
    printf("value of c = %d",*p); // Here * is a Value at operator
    return 0;
}

Output:

value of c = 50

Explanation of the above code:

p is a pointer variable which is holding the address of an integer variable c. Let's say the address of c is "1001". Hence the meaning of the expression *p will be Value at p = Value at 1001 = 50 (i.e, the value of variable c)

Here is another simple code example:

int main() {
    int a,b,c,d;
    int *p;  // Here * is an Indirection operator
    p = &c;
    a = 10;
    b = 5;
    c = 2;
    d = *p+a*b  // Here first * is Value at operator and second * is a Multiplication operator
    printf("value of d = %d", d);
    return 0;
}

Output:

value of d = 52

In the above code, p is a pointer variable which is holding the address of an integer variable c. Let's say the address of c is "1001". Hence the meaning of the expression *p+a*b will be as below:

d = *p+a*b

d = value at p + a multiplication b

d = value at 1001 + 10 multiplication 5

d = 2 + 50

d = 52

How about putting more than one * together?

Well, here is the final and a little complex example to understand this.

int main() {
    int a,b,c,d;
    int *p,*q;  // Here * is an Indirection operator
    int **r;  // Here ** is the indrection operator for declaration of a double pointer (pointer to pointer)
    p = &c;
    q = &a;
    r = &p;
    a = 10;
    b = 5;
    c = 2;
    d = **r + *q * b;
    printf("value of d = %d", d);
    return 0;
}

Output:

value of d = 52

Explanation of the above code:

Let's assume addresses of variables a and c are 1001 and 2002 respectively and the address of pointer variable p is 3003. We can solve the below expression as:

d = **r + *q * b

d = value at (value at r)) + value at (q) multiplication (b)

d = value at (value at 3003) + value at (1001) multiplication b

d = value at (2002) + 10 multiplication 5

d = 2 + 50

d = 52

Thanks for reading. Hope you understood everything about the mystery!