function prototypes and parameters

 pass by value

 you'll dive deeper into the mechanics of functions

 exploring how to declare them properly

 pass information to them 

and understand how C handles function arguments

function prototypes 

declarations

what is a function prototype

a function prototype is essentially a declaration of a function

 it tells the compiler about the function's existence

 its name

 return type

 and the types of parameters it expects

why are prototypes important

type checking

the compiler uses the prototype to check if your function calls are correct 

eg that you're passing the right number and types of arguments

early declaration

 prototypes allow you to define the main logic of your program first main function

 place function definitions later in the code

 this makes your code more readable and organized

syntax

c

<return type> functionName(parameter type1, parameter type2, ...);

example

c

int addNumbers(int num1, int num2); // Function prototype for a function that adds two integers

 function parameters

what are parameters

parameters are variables declared in the function prototype and definition that receive values from the function call

they act as placeholders for the actual values you want the function to work with

pass by value

in c function parameters are passed by value by default

this means a copy of the arguments value is made 

and passed into the function

any modifications made to the parameter inside the function do not affect the original variable in the calling code

this is important for preserving the integrity of your data outside the function

example

c

#include <stdio.h>

void modifyValue(int num) {

    num = num * 2;  // Modify the local copy of 'num'

    printf("Inside function: num = %d\n", num); 

}

int main() {

    int x = 5;

    printf("Before calling function: x = %d\n", x);

    modifyValue(x); // Pass a copy of 'x'

    printf("After calling function: x = %d\n", x); // 'x' remains unchanged

    return 0;

}

output

before calling function x = 5

inside function num = 10

after calling function x = 5

key points

function prototype

 declare functions before they are used to ensure proper type checking

pass by value

 c passes arguments by value by default

 meaning modifications inside the function do not affect the original variables

hands on exercise

create a function calculateCircleArea 

that takes the radius of a circle as a parameter and returns the area

in the main function

 prompt the user to enter a radius

call calculateCircleArea to calculate the area and display the result to the user.

course syllabus