C Programming Tutorial for Beginners

// Declare for use the standard IO library stdio.h.
#include<stdio.h>

int main() {

	// printf is a function of the library stdio.h
	// This is a function to print out a text to console.
	// \n is the newline character.
	printf("Hello!, This is your first C example.\n");

	// Print out the message, the application will end.
	printf("Exit!");

	// This Function returns 0.
	return 0;

}

// Declare for use the standard IO library stdio.h.
#include <stdio.h>

// Declare for use float.h library.
#include <float.h>


int main() {

	// The sizeof(type) function
	// returns the number of bytes to store data types
	printf("Storage size for float : %d \n", sizeof(float));

	// FLT_MIN is constant, the minimum value of float data type.
	// This constant is defined in the library float.h
	printf("Minimum float positive value: %E\n", FLT_MIN);

	// FLT_MAX is constant, the maximum value of float data type.
	// This constant is defined in the library float.h
	printf("Maximum float positive value: %E\n", FLT_MAX);

	// FLT_DIG is constant, the maximum number of decimal fraction.
	// This constant is defined in the library float.h
	printf("Precision value: %d\n", FLT_DIG);

	return 0;

}

// Syntax
if ( condition ) {

	// Do something here
}

// Example 1:
if ( 5 < 10 ) {
	printf( "Five is now less than ten");
}

// Example 2:
if ( true ) {
	printf( "Do something here");
}

// Note that there will be only at most one block can be run.
// Program tests conditions from top to bottom.
// When meeting a condition in which the correct block will be run,
// and the program does not check to the remaining conditions.
...

// If condition 1 is true then ...
if ( condition1) {

	// Do something when condition 1 is true.
}
// Else if condition 2 is true, then ...
else if( condition2 ) {

	// Do something when condition 2 is true
	// (Condition 1 is false).
}
// Else if condition N is true, then ...
else if( conditionN ) {
	// Do something when condition 2 is true
	// (The above conditions are false).
}
// The remaining cases.
else {
	// Do something here.
}

// Declare to use standard IO Library.
#include <stdio.h>

int main_IfElseExample() {

	// Declare a number representing your age.
	int age;

	printf("Please enter your age: \n");

	// Sometimes printf does not print out your message to Console immediately.
	// Using  fflush(stdout) to print out message to Console immediately.
	// Note: stdout is a variable of stream which is printed out the screen.
	// (It is defined in the stdio.h library)
	fflush (stdout);

	// scanf function will wait you type into a text from the keyboard
	// (And press Enter to complete).
	// It will scan to take a number (Specify by %d parameter)
	// and assign to the age variable.
	scanf("%d", &age);

	// Check if age is less than 80 then ...
	if (age < 80) {
		printf("You are pretty young");
	}

	// Else if the age is between 80 and 100 then
	else if (age >= 80 && age <= 100) {
		printf("You are old");
	}
	// Else (The remaining cases)
	else {
		printf("You are verry old");
	}

	return 0;
}

// Use the switch to check the value of a variable.
switch ( a_variable ) {
	case value1:
		// Do something here, if a_variable == value1
		break;
	case value2:
		// Do something here, if a_variable == value2
		break;

	default:
		// Do something here
		// if the value of the variable is different from the values listed above.
		break;
}

#include <stdio.h>

int main() {

	// Asks the user to choose one option.
	printf("Please select one option:\n");

	printf("1 - Play a game \n");
	printf("2 - Play music \n");
	printf("3 - Shutdown computer \n");

	fflush (stdout);

	// Declare an variable.
	int option;

	// scanf function will wait for user to enter text from the keyboard
	// (And press enter to complete).
	// It will scan to get a number (Specify by parameter %d)
	// And convert to int and asign to 'option' variable.
	scanf("%d", &option);

	// Check the value of 'option'.
	switch (option) {

	case 1:
		printf("You choose to play the game \n");
		break;
	case 2:
		printf("You choose to play the music \n");
		break;
	case 3:
		printf("You choose to shutdown the computer \n");
		break;
	default:
		printf("Nothing to do...\n");
		break;
	}

	fflush(stdout);

	return 0;

}

#include <stdio.h>

int main() {

	// Declare variable 'option' and assigns the value of 3.
	int option = 3;

	printf("Option = %d \n", option);

	// Check the value of 'option'
	switch (option) {

	case 1:
		printf("Case 1 \n");
		break;
	case 2:
		printf("Case 2 \n");
		// No break
	case 3:
		printf("Case 3 \n");
		// No break
	case 4:
		printf("Case 4 \n");
		// No break
	case 5:
		printf("Case 5!!! \n");
		break;
	default:
		printf("Nothing to do...\n");
		break;
	}

	fflush (stdout);

	return 0;

}

for ( variable_initialization; condition; variable_update ) {
	// Code to execute while the condition is true.
}

// Example 1:
// Create variable x and assign value of 0 to it.
// Check condition is x < 5.
// If x < 5 is true then execute this block.
// Increase x by 1 after each iteration.
for (int x = 0; x < 5; x = x + 1) {
	// Do something here when x < 5 is true.
}

// Example 2:
// Create variable x and assign value of 2 to it.
// Check condition is x < 15
// If x < 15 is true then execute this block.
// Increase x by 3 after each loop.
for (int x = 2; x < 15; x = x + 3) {
	// Do something here when x < 15 is true.
}

#include <stdio.h>

int main() {

	printf("For loop example\n");

	// Sometimes printf does not print out your message to Console immediately.
	// Using  fflush(stdout) to print out message to Console immediately.
	// Note: stdout is a variable of stream which is printed out the Console.
	// (It is defined in the stdio.h library).
	fflush (stdout);

	// Declare variable x and assign value of 2.
	// Check condition is x <15
	// If x < 15 is true, then run this block.
	// Increase the value of x by 3 after each iteration.
	for (int x = 2; x < 15; x = x + 3) {
		printf("\n");
		printf("Value of x = %d \n", x);
		fflush(stdout);
	}
	return 0;

}

while ( condition ) {

	// When condition is true then execute the block.
}

// Example 1:
// Declare a variable x.
int x = 2;

while ( x < 10) {
	// Do something here when x < 10 is true.
	// ....
	// Update new value to x.
	x = x + 3;
}

#include <stdio.h>

int main() {

	printf("While loop example\n");

	fflush (stdout);

	// Declare variable x and assign value of 2.
	int x = 2;

	// Check condition is x < 10.
	// If x < 10 then run the block.
	while (x < 10) {
		printf("Value of x = %d \n", x);

		x = x + 3;
		fflush(stdout);
	}
	return 0;

}

// The characteristics of 'do-while' loop is that it execute block at least 1 time.
// After each iteration it checks the conditions for the next iteration.
do {

	// Do something here.
}while ( condition );  // Note: Need ';'.

#include <stdio.h>

int main() {

	printf("Do-While loop example\n");

	fflush (stdout);

	// Create variable x and assign value of 2.
	int x = 2;

	// The characteristics of 'do-while' loop is that it execute block at least 1 time.
	// Then check conditions whether continuing to run this block or not.
	do {
		printf("Value of x = %d \n", x);

		x = x + 3;
		fflush(stdout);
	} while (x < 10); // Note: ==> Need ';'

	return 0;

}

#include <stdio.h>

int main() {

	printf("Break example\n");

	fflush (stdout);

	// Create a variable x and assigns the value of 2.
	int x = 2;

	while (x < 15) {

		printf("----------------------\n");
		printf("x = %d \n", x);

		// Check if x = 5, then exit the the loop.
		if (x == 5) {
			break;
		}
		// Increasing x by 1 (Short for x = x + 1).
		x++;
		printf("x after ++ = %d \n", x);

	}
	return 0;

}

#include <stdio.h>

int main() {

	printf("Continue example\n");

	fflush (stdout);

	// Create variable x, and assign value of 2.
	int x = 2;

	while (x < 7) {

		printf("----------------------\n");
		printf("x = %d \n", x);

		// % is operator returns remainder.
		// If x is even, then ignore the below line of the 'continue',
		// to continue the new iteration (if any).
		if (x % 2 == 0) {
			// Increase x by 1 (Short for x = x + 1).
			x++;
			continue;
		} else {
			// Increase x by 1 (Short for x = x + 1).
			x++;
		}
		printf("x after ++ = %d \n", x);

	}
	return 0;

}

// Way 1:
// Declare an array of int numbers, specifying the elements.
int years[] = { 2001, 2003, 2005, 1980, 2003 };

// Way 2:
// Declare an array of 5 elements,
// specify the value for the first 3 elements.
int age[5] = { 20, 10, 50 };

// Way 3:
// Declare an array of floats, specifying the number of elements.
// (Size of 3)
float salaries[3];

#include <stdio.h>

int main() {

	// Way 1:
	// Declare an array with elements.
	int years[] = { 2001, 2003, 2005, 1980, 2003 };

	// Print out size in bytes of int type.
	printf("Sizeof(int) = %d \n", sizeof(int));

	// Size in bytes of array
	printf("Sizeof(years) = %d \n", sizeof(years));

	int arrayLength = sizeof(years) / sizeof(int);

	printf("Element count of array years = %d \n\n", arrayLength);

	// Use a for loop to print out the elements of the array.
	for (int i = 0; i < arrayLength; i++) {
		printf("Element at %d = %d \n", i, years[i]);
	}

	fflush (stdout);

	// Way 2:
	// Declare an array of size 3.
	float salaries[3];

	// Assign values to the elements.
	salaries[0] = 1000;
	salaries[1] = 1200;
	salaries[2] = 1100;

	return 0;

}

// Declare a two-dimensional array.
// (3 rows and 5 columns)
int a[3][5] = { { 1, 2, 3, 4, 5 },
		        { 0, 3, 4, 5, 7 },
				{ 0, 3, 4, 0, 0 } };

// Declare an array,
// specify the number of rows, number of columns
int a[3][5];

#include <stdio.h>

int main() {

	// Declare a two-dimensional array (3 rows and 5 columns)
	int a[3][5] = { { 1, 2, 3, 4, 5 }, { 0, 3, 4, 5, 7 }, { 0, 3, 4, 0, 0 } };

	// Use a for loop to print out the elements of the array.
	for (int row = 0; row < 3; row++) {
		for (int col = 0; col < 5; col++) {
			printf("Element at [%d,%d] = %d \n", row, col, a[row][col]);
		}
	}

	fflush (stdout);

	return 0;
}

type *variable-name;

// Declare a variable type of int.
int var = 120;

// Declare a pointer (point to address of type int).
int *ip;

// Assign value for ip (Point to address of 'var')
ip = &var;

// Using * to access the value of variable that pointer point to.
int var2 = *ip;

#include <stdio.h>

int main() {

	// Declare a variable
	int var = 120;

	// Declare a pointer.
	int *ip;

	// Assign the address of 'var' to pointer.
	ip = &var;

	// Print out the address of 'var' variable.
	printf("Address of var variable: %x \n", &var);

	// Print out address stored in 'ip' variable.
	printf("Address stored in ip variable: %x \n", ip);

	// Access the value of the variable that the pointer is pointing to.
	printf("Value of *ip variable: %d\n", *ip);

	fflush (stdout);

	int var2 = *ip;

	return 0;

}

#include <stdio.h>

int main() {

	// Declare a pointer.
	// Do not assign any value for this pointer.
	// It randomly pointed to certain memory region.
	int *pointer1;

	// Print out the address of pointer1.
	printf("Address of pointer1 is %x \n", pointer1);

	// Check if pointer1 is not NULL.
	if (pointer1) {
		// Print out the value, that the pointer1 point to.
		printf("Value of *pointer1 is %d \n", *pointer1);
	}

	// Declare a pointer.
	// Point to nothing (NULL).
	int *pointer2 = NULL;

	// Print out address of pointer2.
	printf("Address of pointer2 is %x \n", pointer2);

	// If pointer2 is NULL then print out message.
	if (!pointer2) {
		printf("pointer2 is NULL");
	} else {
		// NOTE:
		// If pointer2 is NULL, access to the value of *pointer2
		// will receive an error and stop the program.
		printf("Value of *pointer2 is %d \n", *pointer2);
	}

	fflush (stdout);

	return 0;
}