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Pass by Pointers

1. Pass By Value

Other Methods of Parameter Passing

This technique uses a pointer. In function we pass memory address (pointer) of a variable rather than passing the actual value of variable. This passing technique allows the function to access and modify the content at that particular memory location.

Example of Pass by Pointers

C




// C program to demonstrate the pass by pointer in Function
 
#include <stdio.h>
 
// Function to modify the value passed as pointer to an int
void modifyVal(int* myptr)
{
    // Access and modifying the value pointed by myptr
    *myptr = *myptr + 5;
}
 
int main()
{
 
    int x = 5;
    int* myptr = &x;
 
    // Passing the pointer ptr to the function
    modifyVal(myptr);
 
    // printitng the modified value of x
    printf("Modified value of x is: %d\n", x);
    return 0;
}
 






                        









													
													
												

												
												

													
													
Output


Modified value of x is: 10



													
													
												

												
												

													
													
Shortcomings of Pass by Pointers

													
													
												

												
												

													
													
    

  • Pointers can be null so null pointer Issues arises if properly not checked.
    • 

  • If more than one pointers point to the same memory location then changes made by one pointer affect other the other pointers which points to same memory location.
    • 

  • memory management should be done effectively using function like malloc and free.
    • 


													
													
												

												
											

											
											

												
Parameter Passing Techniques in C

												
												

													
													
In C, there are different ways in which parameter data can be passed into and out of methods and functions. Let us assume that a function B() is called from another function A(). In this case, A is called the “caller function” and B is called the “called function or callee function”. Also, the arguments which A sends to B are called actual arguments and the parameters of B are called formal arguments.

													
													
												

												
												

													
													
Terminology

													
													
												

												
												

													
													
    

  • Formal Parameter: A variable and its type as it appears in the prototype of the function or method.
    • 

  • Actual Parameter: The variable or expression corresponding to a formal parameter that appears in the function or method call in the calling environment.
    • 

  • Modes:

      

    • IN: Passes info from caller to the callee.
      • 

    • OUT: Callee writes values in the caller.
      • 

    • IN/OUT: The caller tells the callee the value of the variable, which the callee may update.
      • 

    

    • 


													
													
												

												
											

										


										
										

											
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														1. Pass By Value

													

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												1. Pass By Value
											
											
										

										

											
											
												Other Methods of Parameter Passing