What is the difference between passing data by value and by reference

The value of a reference type is a pointer to the data elsewhere in memory. This means that when you pass a reference type by value, the procedure code has a pointer to the underlying element's data, even though it cannot access the underlying element itself.

For example, if the element is an array variable, the procedure code does not have access to the variable itself, but it can access the array members. When you pass a nonmodifiable element as an argument, the procedure can never modify it in the calling code, whether it is passed ByVal or ByRef.

For a modifiable element, the following table summarizes the interaction between the element type and the passing mechanism. Feedback will be sent to Microsoft: By pressing the submit button, your feedback will be used to improve Microsoft products and services. Privacy policy. In other words, the function gets access to the actual variable. An example is as follows. Figure 2: C program with pass by reference. The variable value stores integer 5.

Thus, the function gets this value. The newValue is a pointer. It points to the original memory location called value. The function adds 5 to the original value pointed by newValue. Then, the calculated value is returned and stored into the newValue variable.

In this method, the memory location passes to the function. Therefore, the changes are made to the original value. Hence, this method is called Pass by Reference. Call by Value, variables are passed using a straightforward method whereas Call by Reference, pointers are required to store the address of variables.

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The parameter that we will pass in is the num variable. As we saw with pass-by-reference, when we tried to mutate the object in newJohn , we were essentially referencing the object stored in the variable john and changing the object. This is because when we pass num into the function, it creates a copy and it is given its own space in memory. When we console. The value const num is not changed! Understanding PBV vs PBR is helpful because if you are writing code and you want to set one variable equal to another variable, or in the example above, pass a variable into a function as an argument, you need to know whether the value will be pass-by-value or pass-by-reference.

This will help you avoid errors when working with your data. Coding tutorials and news. The developer homepage gitconnected. Sign in.

Pass-By Value vs.