return value of assignment in c

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C Function Arguments and Function Return Values

Prerequisite: Functions in C

Call by Value

Call by value in C is where in the arguments we pass value and that value can be used in function for performing the operation. Values passed in the function are stored in temporary memory so the changes performed in the function don’t affect the actual value of the variable passed. To explore how functions interact with data structures, the C Programming Course Online with Data Structures covers the practical use of functions in various programming scenarios.

Call by Reference

Call by reference is the method in C where we call the function with the passing address as arguments. We pass the address of the memory blocks which can be further stored in a pointer variable that can be used in the function. Now, changes performed in the values inside the function can be directly reflected in the main memory.

Types of Function According to Arguments and Return Value

Functions can be differentiated into 4 types according to the arguments passed and value returns these are:

• Function with arguments and return value
• Function with arguments and no return value
• Function with no arguments and with return value
• Function with no arguments and no return value

1. Function with arguments and return value 

2. function with arguments but no return value.

When a function has arguments, it receives any data from the calling function but it returns no values. These are void functions with no return values.

3. Function with no argument and no return value

When a function has no arguments, it does not receive any data from the calling function. Similarly, when it does not return a value, the calling function does not receive any data from the called function. 

4. Function with no arguments but returns a value

There could be occasions where we may need to design functions that may not take any arguments but returns a value to the calling function. An example of this is getchar function which has no parameters but it returns an integer and integer-type data that represents a character. 

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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 −

C Functions

C structures, c reference, c operators.

Operators are used to perform operations on variables and values.

In the example below, we use the + operator to add together two values:

Although the + operator is often used to add together two values, like in the example above, it can also be used to add together a variable and a value, or a variable and another variable:

C divides the operators into the following groups:

• Arithmetic operators
• Assignment operators
• Comparison operators
• Logical operators
• Bitwise operators

Arithmetic Operators

Arithmetic operators are used to perform common mathematical operations.

Assignment Operators

Assignment operators are used to assign values to variables.

In the example below, we use the assignment operator ( = ) to assign the value 10 to a variable called x :

The addition assignment operator ( += ) adds a value to a variable:

A list of all assignment operators:

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Comparison Operators

Comparison operators are used to compare two values (or variables). This is important in programming, because it helps us to find answers and make decisions.

The return value of a comparison is either 1 or 0 , which means true ( 1 ) or false ( 0 ). These values are known as Boolean values , and you will learn more about them in the Booleans and If..Else chapter.

Comparison operators are used to compare two values.

Note: The return value of a comparison is either true ( 1 ) or false ( 0 ).

In the following example, we use the greater than operator ( > ) to find out if 5 is greater than 3:

A list of all comparison operators:

Logical Operators

You can also test for true or false values with logical operators.

Logical operators are used to determine the logic between variables or values, by combining multiple conditions:

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7 Assignment Expressions

As a general concept in programming, an assignment is a construct that stores a new value into a place where values can be stored—for instance, in a variable. Such places are called lvalues (see Lvalues ) because they are locations that hold a value.

An assignment in C is an expression because it has a value; we call it an assignment expression . A simple assignment looks like

We say it assigns the value of the expression value-to-store to the location lvalue , or that it stores value-to-store there. You can think of the “l” in “lvalue” as standing for “left,” since that’s what you put on the left side of the assignment operator.

However, that’s not the only way to use an lvalue, and not all lvalues can be assigned to. To use the lvalue in the left side of an assignment, it has to be modifiable . In C, that means it was not declared with the type qualifier const (see const ).

The value of the assignment expression is that of lvalue after the new value is stored in it. This means you can use an assignment inside other expressions. Assignment operators are right-associative so that

is equivalent to

This is the only useful way for them to associate; the other way,

would be invalid since an assignment expression such as x = y is not valid as an lvalue.

Warning: Write parentheses around an assignment if you nest it inside another expression, unless that is a conditional expression, or comma-separated series, or another assignment.