10 Differences Between actual parameter and formal parameter

Actual Parameter vs Formal Parameter

What is/are actual parameter?

An actual parameter, also known as an argument, is the value or expression passed to a function or method during its execution. It represents the actual data on which the function operates.

Examples of actual parameters:

  • print("Hello, world!"): Here, “Hello, world!” is the actual parameter passed to the print() function.
  • Math.max(5, 10): In this example, both 5 and 10 are actual parameters passed to the Math.max() function.

Uses of actual parameters:

Actual parameters allow you to provide dynamic or varying inputs to functions. They enable functions to perform operations on different data values without the need for rewriting the function code each time.

What is/are formal parameter?

A formal parameter is a placeholder or variable defined in a function or method signature. It receives the value from the actual parameter passed during function call or method invocation. Formal parameters act as local variables within the function.

Examples of formal parameters:

  • function square(num): Here, num is the formal parameter defined in the square() function.
  • function add(a, b): In this example, both a and b are formal parameters defined in the add() function.

Uses of formal parameters:

Formal parameters define the structure and input requirements of a function. They allow functions to operate on different values without knowing the specific values in advance. Formal parameters also enable code reuse and function parameterization.

Differences between actual parameter and formal parameter:

Difference Area Actual Parameter Formal Parameter
Definition The value or expression passed to a function during its execution The placeholder or variable defined in a function or method signature
Usage Provides the actual data on which a function operates Acts as a local variable within the function
Role Represents the arguments passed when calling a function Receives the values from the actual parameters
Declaration Not explicitly declared; directly passed during function call Declared in the function or method signature
Number Multiple actual parameters can be passed to a function Number of formal parameters must match the number of actual parameters
Value Assignment Assigned when invoking the function or method Assigned when calling the function or method with actual parameters
Visibility Visible and accessible within the function scope Visible and accessible only within the function or method where they are defined
Scope Defined outside the function Local to the function
Value Changes Changes made to actual parameters do not affect the calling environment Changes made to formal parameters do not affect the calling environment
Flexibility Allows passing different values each time the function is called Allows reusing the same function with different values


The main difference between actual parameters and formal parameters lies in their role and visibility. Actual parameters are the values passed to functions, while formal parameters are variables that receive these values. Both are essential in function operations and enable the flexibility and reusability of code.

People Also Ask:

Q: Can a function have more formal parameters than actual parameters?

A: No, the number of formal parameters must match the number of actual parameters passed to a function. Otherwise, a mismatch error may occur.

Q: What happens if we don’t pass all the required actual parameters?

A: If all the required actual parameters are not passed, the function may throw an error. It depends on the specific programming language and its parameter requirements.

Q: Can formal parameters have default values?

A: Yes, some programming languages allow you to define default values for formal parameters. These default values are used if no corresponding actual parameter is provided during the function call.

Q: Can actual parameters be variables?

A: Yes, actual parameters can be both literal values and variables. They can hold any valid expression or data that satisfies the function’s parameter requirements.

Q: Is the order of actual parameters important?

A: In most programming languages, the order of actual parameters must match the order of formal parameters in the function or method signature. Changing the order may lead to incorrect results.

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