If the argument within the parentheses of a function call is a variable, constant (or some other expression) it means that it is first evaluated and a COPY is then passed to the function as its input.
The function uses the copy of the passed in argument, and executes any statements upon that copy locally within the function.
Once the execution within the function is complete, control returns to the point of which the call was made, and any locally changed data within the called function is lost.
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#include <stdio.h> void function(int myInt); //declare the function prototype int main() { int myVar = 42; //define a local variable printf("1st value of myVar in main: %dn", myVar); //print value of myVar function(myVar); //call and pass myVar to globalFunction printf("2nd value of myVar in main: %dn", myVar); //print value of myVar return 0; } void function(int myVar) { //void function since nothing being returned printf("1st value of myVar in function: %dn", myVar); //print value of myVar myVar = 17; //variable is now being assigned a new value printf("2nd value of myVar in function: %dn", myVar); //print value of myVar } |
Compile & run:
| 1st value of myVar in main: 42 1st value of myVar in function: 42 2nd value of myVar in function: 17 2nd value of myVar in main: 42 |