Function Parameters and Pointers in C Language

In C language, function parameters can be passed in two ways: by value and by reference. When a parameter is passed by value, a copy of the value is passed to the function. Any changes made to the parameter inside the function do not affect the original variable. When a parameter is passed by reference, a pointer to the memory location of the variable is passed to the function. Any changes made to the parameter inside the function affect the original variable.

Passing a parameter by reference can be achieved by using a pointer. A pointer variable is declared by placing an asterisk (*) before the variable name, followed by the type of the variable it points to. For example, the following declares a pointer variable p that points to an integer variable:

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int* p;

When a pointer variable is passed as an argument to a function, the function receives the memory address of the variable, not a copy of its value.

Here is an example of passing an integer variable by reference using a pointer:

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#include <stdio.h> void increment(int* p) {    (*p)++; } int main() {    int x = 10;    increment(&x);    printf("x = %d\n", x);    return 0; }

In this example, the increment() function takes a pointer to an integer as an argument, which allows it to directly modify the value of the integer variable x in the main function.

It's also important to mention that arrays and strings are passed to functions as pointers by default in C, so when we pass an array or a string to a function, it receives a pointer to the first element of the array or string, and it can directly access the memory location of the array or string elements and make changes to it.