Difference Between Actual and Formal Parameters | Actual vs Formal

By Mohit Uniyal|Updated : April 21st, 2022

Difference Between Actual and Formal Parameters: The parameters are used to either pass or send out the information in a program. They are an important part of a program. It is always important to define the purpose of the parameter in a program. The major difference between actual and formal parameters is that the actual parameter is used to invoke or pass the information while executing the program whereas formal parameters are declared while calling the function. 

It is an essential part of any programming language to use the function. They are used to perform a specific task. Let us know more about the difference between actual and formal parameters in the coming sections. 

Table of Content

What are the Actual Parameters?

Before learning about the difference between Actual and Formal parameters, let us learn about them in brief. An actual parameter is the value of a function that is passed when the function is being invoked. The caller will assign the actual value. It is a parameter that is determined while inviting a subroutine.  

Example:

#include <stdio.h>

void multiplication (int x, int y) {

int multiplication;

addition = x*y;

printf(“%d”,multiplication);

}

void main () {

multiplication (2,3);

multiplication (4,5);

}

What are the Formal Parameters?

Let us learn about the formal parameters before finally discussing the difference between Actual and Formal parameters. A formal parameter is defined while determining the subroutine. Formal parameters are also used in the header of the function. 

The syntax of the formal parameters is:

<return type> <method name> (formal parameters) {

//set of statements to be executed

}

Difference Between Actual and Formal Parameters

The major difference between actual and formal parameters is that formal parameters are defined when the function is called whereas actual parameters are defined when the function is invoked. Let us see other differences between actual and formal parameters in the table provided below:

Difference Between Actual and Formal Parameters
Actual ParametersFormal Parameters
Defined when it is invoked.Defined when the function is called.
Passed on calling a functionThey will be in the called function. 
Data types will not be mentioned.The data type must be included.
They are written in the function call.They are written in the function definition. 
They may be constant values.Can be local variables.

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FAQs

  • The major difference between actual and formal parameters is that formal parameters are declared on calling the function and the actual parameter is declared on invoking. The actual parameters can carry constant values whereas formal parameters carry variables.

  • An actual parameter is the variable that will be transferred on calling by the function. They do not require defining of the data types.

  • The formal parameters are defined when the function is being declared. The values are only accepted on and during declaring. They are with data types. The parameters addressed in it are known as formal parameters.

  • In the formal parameters data types are required to be assigned and defined necessarily while in actual parameters, it is not mandatory to define the data types.

  • The similarity between formal and actual parameters that both of them are defined for functions, always included within parenthesis. They are specifically assigned per program.

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