Difference Between Actual and Formal Parameters

By Mohit Uniyal|Updated : September 27th, 2022

The difference Between Actual and Formal Parameters is that the actual parameter is used to invoke or pass the information while executing the program. In contrast, formal parameters are declared while calling the function. Actual and Formal Parameters are an important part of a program.

It is always important to define the purpose of the parameter in a program. Let us know more about the difference between actual and formal parameters in the coming sections, along with knowing what is actual and formal parameters. 

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.

Key Differences 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.They can be local variables.

Actual and Formal Parameters

The parameters are used to either pass or send out the information in a program. It is an essential part of any programming language to use the function.

Difference between Actual and Formal Parameters PDF

They are used to perform a specific task. There are two types of parameters that are widely used:

  • Actual Parameters
  • Formal Parameters

What are the Actual Parameters?

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 of Actual Parameters

#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. 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

}

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FAQs on Difference Between Actual and Formal Parameters

  • 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 actual and formal parameters is that both are defined for functions, always included within parenthesis. They are specifically assigned per program.

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