What Is the Difference between Pass by Value and Pass by Reference?

Computer programming is a process where professionals write codes to instruct a computer or an application to perform specific tasks. Each programming language offers functions that are a set of commands or statements that execute the task when call.

These sets of commands take inputs or some arguments to give return outputs. These arguments can either be passed by value or reference. Understanding the distinction between pass-by value and reference is crucial element in programming.

So, what is the difference between pass by value and pass by reference? Pass by value is when the parameter value copies to another variable. On the other hand, pass by reference is where the actual parameter passes to the function.

These programming statements allow professionals to manage and maintain applications or software programs. The table below displays the difference between pass by value and pass by reference in C#.

Difference between Pass by Value and Pass by Reference with Table

Parameters Pass By Value Pass By Reference
Definition It is the process of copying the function parameter value to another. It is the process of passing the actual parameter to the function.
Changes Effect Any tweaks made inside the function are not reflected in the original value. Changes made inside the function are reflected in the original value.
Actual Parameter Makes a copy of the actual parameter. The address of the actual parameter passes to the function.
Association with Function Function gets a copy of the actual content. Function access the original variable content.
Memory Requirement Requires more memory Requires less memory
Time Requirement Needs more time since it involves copying values. Requires less time since there is no copying values.
Application Building a multi-threaded application. Passing objects of large structs or classes.

What Is Pass by Value?

Pass by value is a mechanism of copying function parameter value to another memory location. If you are tweaking a variable within the function, it accesses only the copy.

These changes or modifications will not have any effect on the original value. The value copied to a new memory location is called newValue. The changes are said to be made on the newValue and not the original value.

Below is an illustration of pass by value:

let a = 100;let b = a;a = 90;

console.log(a); // prints 90

console.log(b); // prints 100

Changing the value of “a” does not affect the value of “b”, since different memory is allocated to it on assignment.

What Is Pass by Reference?

Pass by reference is a mechanism where the memory address is passed to the function. The function will get access to the original variable.

When the memory address passes to the function, it alters with the actual variable. The process requires less memory and time since there is no copying issue.

Below is an illustration of pass by reference:

let a = {‘name’ : ‘Rohan’, ‘age’ : 30};

let b = a;

a.name = ‘Sam’;

console.log(a); // prints {‘name’ : ‘Sam’, ‘age’ : 30}

console.log(b); // prints {‘name’ : ‘Sam’, ‘age’ : 30}

Both “a” and “b” variables point to the same object, hence any changes in the value of “a” will update “b” value and vice versa.

Main Difference between Pass by Value and Reference

  1. Pass by value involves copying the function parameter value to another variable. On the other hand, pass by reference involves passing the actual parameters to the function.
  2. Pass by value changes made inside the function are not reflected in the original value. Changes made inside the function of pass by reference are reflected in the original value.
  3. Pass by value makes a copy of the actual parameter, whereas pass by reference passes the address of actual parameter to the function.
  4. Pass by value function gets a copy of the actual content, while pass by reference function access the original variable content.
  5. Pass by value requires more memory since it involves copying values. On the other hand, pass by reference requires less memory since there is no copying.
  6. Pass by value needs more time due to copying of values, whereas pass by reference requires less time.

Similarities between Pass by Value and Reference

  1. Both are involved in programming languages.
  2. Both are ideal in writing efficient and effective programs.
  3. Both make the programs more manageable and easy to maintain.
  4. Both are two methods of calling a function.

Conclusion

So, what is the difference between pass by value and pass by reference in C? The former is a coping mechanism of the function parameter value to another variable, while the latter is the mechanism of passing the actual parameter to the function.

Pass by value changes inside the function are not reflected in the actual value. This happens since the mechanism will make an original parameter copy and require more memory and time.

Pass by reference changes inside the function are reflected in the original value. This happens since the address of the actual parameter passes to the function and will require less memory and time.

Understanding the difference between pass by value and pass by reference with example is crucial.  It will help you overcome challenges associated with pass by value and pass by reference in python.

References

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