MULTIPLE CALLS TO A FUNCTION WITH INPUT/OUTPUT PARAMETERS

Input/Output (I/O) Parameters in C

These are function parameters implemented using pointers that allow a function to receive an initial value, modify it, and have that change persist in the caller's scope.

Passing variables as I/O parameters

To pass a variable for modification, use the address-of operator && during the function call (e.g., modifyValue(&x);) to provide the memory address of the variable.

Dereferencing in I/O parameters

Inside the function, the dereference operator ∗∗ is used to access and update the actual value stored at the address provided by the pointer (e.g., ∗ptr=100;).

State changes with multiple calls

When a function with I/O parameters is called multiple times on the same variable, each call updates the current state of that variable. For example, if addFive(&n) is called twice, the value of n increases by a total of 1010.

Example of multiple calls to a pointer-based function

Function: void applyStep(int *val) { *val += 1; }

• Execution:

  1. int count = 0;

  2. applyStep(&count); (count becomes 11)

  3. applyStep(&count); (count becomes 22)