#include <stdio.h>
#include <string.h>

int main()
{
	char array [] = "Hello"; // array has 6 characters

	printf("Length: %lu\n", strlen(array)); // 5
	printf("String: %s\n", array); // Hello

	for(int i = 0; i < 6; i++)
		printf("|%c|\n", array[i]);

	return 0;
}
		

#include <stdio.h>

int main()
{
	char str[100];

	printf("Enter a string: \n");

	scanf("%s", str); // read the first token

	printf("%s\n", str);

	return 0;
}

//Hello World
//Hello
		

#include <stdio.h>

int main()
{
	char str[100];

	printf("Enter a string:\n");

	fgets(str, sizeof(str), stdin); // read the whole line
	printf("%s\n", str);

	return 0;
}

//Hello World
//Hello World
//
		

#include <stdio.h>
#include <string.h>

char *getString()
{
	char *str = "Hello World";

	return str;
}

int main()
{
	char *str = getString();

	printf("Length: %lu\n", strlen(str)); // 5
	printf("String: %s\n", str);

	return 0;
}
		

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

char *getString()
{
	char *str = (char *) malloc(100*sizeof(char));
	scanf("%s", str); // read the first token

	return str;
}

int main()
{
	char *str = getString();

	printf("Length: %lu\n", strlen(str)); // 5
	printf("String: %s\n", str);

	free(str);

	return 0;
}

//Hello World
//Hello
		

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

char *getString()
{
	char *str = (char *) malloc(100*sizeof(char));
	fgets(str, 100, stdin);

	return str;
}

int main()
{
	char *str = getString();

	printf("Length: %lu\n", strlen(str)); // 5
	printf("String: %s\n", str);

	free(str);

	return 0;
}

//Hello World
//Hello World
//
		

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

int main()
{
	char *str1 = "Hello";
	char *str2 = "Hello";
	char *str3 = "World";

	// strlen
	printf("Length: %lu\n", strlen(str1)); // 5

	// strcmp
	// equal, 0; less than, negative integer; greater than, positive integer
	printf("Compare: %d\n", strcmp(str1, str2)); // 0
	printf("Compare: %d\n", strcmp(str1, str3)); // -15
	//printf("String: %s\n", str);
	
	// memcpy
	char *str4 = (char *)malloc(strlen(str1)+1);
	memcpy(str4, str1, strlen(str1)+1);
	printf("Copy: %s\n", str4);

	// strcat
	char *str5 = (char *)malloc(strlen(str1)+strlen(str3)+1);
	memcpy(str5, str1, strlen(str1));
	strcat(str5, str3); // append str2 to str1
	printf("Concatnate: %s\n", str5); // HelloWorld

	// sub string
	char *str6 = (char *) malloc(3);
	memcpy(str6, &str5[5], 2);
	str6[2] = '\0';
	printf("Substring: %s\n", str6); // Wo

	return 0;
}
		

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

int getInteger()
{
	printf("Enter an integer number:\n");
	char str[100];
	scanf("%s", str); // read the first token

	return atoi(str);
}

double getDouble()
{
	printf("Enter a double number:\n");
	char *str = (char *) malloc(100*sizeof(char));
	scanf("%s", str); // read the first token

	double num = atof(str);

	free(str);

	return num;
}

int main()
{
	int age = getInteger();

	double pi = getDouble();

	printf("%d\n", age);
	printf("%f\n", pi);

	return 0;
}
		

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

int main()
{
	// pointer
	char * str = "Hello"; // constant char data, do not free

	//str[0] = 'W'; // bus error
	str = "World";
	printf("%s\n", str); //World

	// array
	char str2 [] = "Hello";
	str2[0] = 'W';
	//str2 = "World"; // not allowed
	printf("%s\n", str2); //Wello

	return 0;
}