assignment operator pointer in c

Example of Augmented Arithmetic and Assignment Operators

There can be five combinations of bitwise operators with the assignment operator, "=". Let's look at them one by one.

Example of Augmented Bitwise and Assignment Operators

Practice problems on assignment operators in c, 1. what will the value of "x" be after the execution of the following code.

The correct answer is 52. x starts at 50, increases by 5 to 55, then decreases by 3 to 52.

2. After executing the following code, what is the value of the number variable?

The correct answer is 144. After right-shifting 73 (binary 1001001) by one and then left-shifting the result by two, the value becomes 144 (binary 10010000).

Benefits of Using Assignment Operators

• Simplifies Code: For example, x += 1 is shorter and clearer than x = x + 1.
• Reduces Errors: They break complex expressions into simpler, more manageable parts thus reducing errors.
• Improves Readability: They make the code easier to read and understand by succinctly expressing common operations.
• Enhances Performance: They often operate in place, potentially reducing the need for additional memory or temporary variables.

Best Practices and Tips for Using the Assignment Operator

While performing arithmetic operations with the same variable, use compound assignment operators

• Initialize Variables When Declaring int count = 0 ; // Initialization
• Avoid Complex Expressions in Assignments a = (b + c) * (d - e); // Consider breaking it down: int temp = b + c; a = temp * (d - e);
• Avoid Multiple Assignments in a Single Statement // Instead of this a = b = c = 0 ; // Do this a = 0 ; b = 0 ; c = 0 ;
• Consistent Formatting int result = 0 ; result += 10 ;

When mixing assignments with other operations, use parentheses to ensure the correct order of evaluation.

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Assignment and shorthand assignment operator in C

Quick links.

• Shorthand assignment

Assignment operator is used to assign value to a variable (memory location). There is a single assignment operator = in C. It evaluates expression on right side of = symbol and assigns evaluated value to left side the variable.

For example consider the below assignment table.

The RHS of assignment operator must be a constant, expression or variable. Whereas LHS must be a variable (valid memory location).

Shorthand assignment operator

C supports a short variant of assignment operator called compound assignment or shorthand assignment. Shorthand assignment operator combines one of the arithmetic or bitwise operators with assignment operator.

For example, consider following C statements.

The above expression a = a + 2 is equivalent to a += 2 .

Similarly, there are many shorthand assignment operators. Below is a list of shorthand assignment operators in C.

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Assignment Operators in C

In C language, the assignment operator stores a certain value in an already declared variable. A variable in C can be assigned the value in the form of a literal, another variable, or an expression.

The value to be assigned forms the right-hand operand, whereas the variable to be assigned should be the operand to the left of the " = " symbol, which is defined as a simple assignment operator in C.

In addition, C has several augmented assignment operators.

The following table lists the assignment operators supported by the C language −

Simple Assignment Operator (=)

The = operator is one of the most frequently used operators in C. As per the ANSI C standard, all the variables must be declared in the beginning. Variable declaration after the first processing statement is not allowed.

You can declare a variable to be assigned a value later in the code, or you can initialize it at the time of declaration.

You can use a literal, another variable, or an expression in the assignment statement.

Once a variable of a certain type is declared, it cannot be assigned a value of any other type. In such a case the C compiler reports a type mismatch error.

In C, the expressions that refer to a memory location are called "lvalue" expressions. A lvalue may appear as either the left-hand or right-hand side of an assignment.

On the other hand, the term rvalue refers to a data value that is stored at some address in memory. A rvalue is an expression that cannot have a value assigned to it which means an rvalue may appear on the right-hand side but not on the left-hand side of an assignment.

Variables are lvalues and so they may appear on the left-hand side of an assignment. Numeric literals are rvalues and so they may not be assigned and cannot appear on the left-hand side. Take a look at the following valid and invalid statements −

Augmented Assignment Operators

In addition to the = operator, C allows you to combine arithmetic and bitwise operators with the = symbol to form augmented or compound assignment operator. The augmented operators offer a convenient shortcut for combining arithmetic or bitwise operation with assignment.

For example, the expression "a += b" has the same effect of performing "a + b" first and then assigning the result back to the variable "a".

Run the code and check its output −

Similarly, the expression "a <<= b" has the same effect of performing "a << b" first and then assigning the result back to the variable "a".

Here is a C program that demonstrates the use of assignment operators in C −

When you compile and execute the above program, it will produce the following result −

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Pointer Arithmetics in C with Examples

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• C - Pointer to Pointer (Double Pointer)
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• How to declare a pointer to a function?
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• Pointer vs Array in C
• NULL Pointer in C
• Dangling, Void , Null and Wild Pointers in C
• Near, Far and Huge Pointers in C
• restrict keyword in C

Pointer Arithmetic is the set of valid arithmetic operations that can be performed on pointers. The pointer variables store the memory address of another variable. It doesn’t store any value. 

Hence, there are only a few operations that are allowed to perform on Pointers in C language. The C pointer arithmetic operations are slightly different from the ones that we generally use for mathematical calculations. These operations are:

• Increment/Decrement of a Pointer
• Addition of integer to a pointer
• Subtraction of integer to a pointer
• Subtracting two pointers of the same type
• Comparison of pointers

1. Increment/Decrement of a Pointer

Increment: It is a condition that also comes under addition. When a pointer is incremented, it actually increments by the number equal to the size of the data type for which it is a pointer. 

For Example: If an integer pointer that stores address 1000 is incremented, then it will increment by 4( size of an int ), and the new address will point to 1004 . While if a float type pointer is incremented then it will increment by 4( size of a float ) and the new address will be 1004 .

Decrement: It is a condition that also comes under subtraction. When a pointer is decremented, it actually decrements by the number equal to the size of the data type for which it is a pointer. 

For Example: If an integer pointer that stores address 1000 is decremented, then it will decrement by 4( size of an int ), and the new address will point to 996 . While if a float type pointer is decremented then it will decrement by 4( size of a float ) and the new address will be 996 .

Note: It is assumed here that the architecture is 64-bit and all the data types are sized accordingly. For example, integer is of 4 bytes.

Example of Pointer Increment and Decrement

Below is the program to illustrate pointer increment/decrement:

Note: Pointers can be outputted using %p, since, most of the computers store the address value in hexadecimal form using %p gives the value in that form. But for simplicity and understanding we can also use %u to get the value in Unsigned int form.

2. Addition of Integer to Pointer

When a pointer is added with an integer value, the value is first multiplied by the size of the data type and then added to the pointer.

For Example: Consider the same example as above where the ptr is an integer pointer that stores 1000 as an address. If we add integer 5 to it using the expression, ptr = ptr + 5, then, the final address stored in the ptr will be ptr = 1000 + sizeof(int) * 5 = 1020.

Example of Addition of Integer to Pointer

3. Subtraction  of Integer to Pointer

When a pointer is subtracted with an integer value, the value is first multiplied by the size of the data type and then subtracted from the pointer similar to addition.

For Example: Consider the same example as above where the ptr is an integer pointer that stores 1000 as an address. If we subtract integer 5 from it using the expression, ptr = ptr – 5, then, the final address stored in the ptr will be ptr = 1000 – sizeof(int) * 5 = 980.

Example of Subtraction of Integer from Pointer

Below is the program to illustrate pointer Subtraction:

4. Subtraction of Two Pointers

The subtraction of two pointers is possible only when they have the same data type. The result is generated by calculating the difference between the addresses of the two pointers and calculating how many bits of data it is according to the pointer data type. The subtraction of two pointers gives the increments between the two pointers. 

For Example:   Two integer pointers say ptr1(address:1000) and ptr2(address:1004) are subtracted. The difference between addresses is 4 bytes. Since the size of int is 4 bytes, therefore the increment between ptr1 and ptr2 is given by (4/4) = 1 .

Example of Subtraction of Two Pointer

Below is the implementation to illustrate the Subtraction of Two Pointers:

5. Comparison of Pointers

We can compare the two pointers by using the comparison operators in C. We can implement this by using all operators in C >, >=, <, <=, ==, !=.   It returns true for the valid condition and returns false for the unsatisfied condition. 

• Step 1: Initialize the integer values and point these integer values to the pointer.
• Step 2: Now, check the condition by using comparison or relational operators on pointer variables.
• Step 3: Display the output.

Example of Pointer Comparision

Comparison to null.

A pointer can be compared or assigned a NULL value irrespective of what is the pointer type. Such pointers are called NULL pointers and are used in various pointer-related error-handling methods.

Comparison operators on Pointers using an array

In the below approach, it results in the count of odd numbers and even numbers in an array. We are going to implement this by using a pointer.

• Step 1: First, declare the length of an array and array elements.
• Step 2: Declare the pointer variable and point it to the first element of an array.
• Step 3: Initialize the count_even and count_odd. Iterate the for loop and check the conditions for the number of odd elements and even elements in an array
• Step 4: Increment the pointer location ptr++ to the next element in an array for further iteration.
• Step 5: Print the result.

Example of Pointer Comparison in Array

Pointer Arithmetic on Arrays

Pointers contain addresses. Adding two addresses makes no sense because there is no idea what it would point to. Subtracting two addresses lets you compute the offset between the two addresses. An array name acts like a pointer constant. The value of this pointer constant is the address of the first element.

For Example: if an array is named arr then arr and &arr[0] can be used to reference the array as a pointer.

Below is the program to illustrate the Pointer Arithmetic on arrays:

Program 1:  

Program 2:  

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