C

Function

Pass by value

#include <stdio.h>

void doubleNum(int n)
{
	printf("In fuction: %d, %p\n", n, &n);
	n *= 2;
	printf("In fuction: %d, %p\n", n, &n);
}

int main()
{
	int a = 10;

	printf("Value: %d, Address: %p\n", a, &a);

	doubleNum(a);

	printf("After calling function: %d, %p\n", a, &a);
}

Pass by reference

#include <stdio.h>

void doubleNum(int *n)
{
	printf("In fuction: %d, %p\n", *n, n);
	*n *= 2;
	printf("In fuction: %d, %p\n", *n, n);
}

int main()
{
	int a = 10;

	printf("Value: %d, Address: %p\n", a, &a);

	doubleNum(&a);

	printf("After calling function: %d, %p\n", a, &a);
}

Layout in single file

#include <stdio.h>
#include <time.h>
#include <stdlib.h>

int doubleNum(int n)
{
	int num;
	num = 2*n;

	return num;
}

int main()
{
	srand(time(NULL)); // take a random seed
	int r = rand()%100; // generate a random number within [0, 100)

	printf("Value: %d\n", doubleNum(r));
}

#include <stdio.h>
#include <time.h>
#include <stdlib.h>

int doubleNum(int);

int main()
{
	srand(time(NULL)); // take a random seed
	int r = rand()%100; // generate a random number within [0, 100)

	printf("Value: %d\n", doubleNum(r));
}

int doubleNum(int n)
{
	int num;
	num = 2*n;

	return num;
}

Layout in multiple files

// f3.c
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include "util.h"

int main()
{
	srand(time(NULL)); // take a random seed
	int r = rand()%100; // generate a random number within [0, 100)

	printf("Value: %d\n", doubleNum(r));
}

// util.c
#include "util.h"

int doubleNum(int n)
{
	int num;
	num = 2*n;

	return num;
}

// util.h
#ifndef UTIL_H
#define UTIL_H
int doubleNum(int);
#endif