diff --git a/helloworld/.c b/helloworld/.c
new file mode 100644
index 0000000..cb9c3d9
--- /dev/null
+++ b/helloworld/.c
@@ -0,0 +1,8 @@
+1:  /* 02L01.c: This is my first C program */
+2:  #include <stdio.h>
+3:
+4:  main()
+5:  {
+6:     printf ("Howdy, neighbor! This is my first C program.\n");
+7:     return 0;
+8:  }
\ No newline at end of file
diff --git a/helloworld/H2_E2.c b/helloworld/H2_E2.c
new file mode 100644
index 0000000..9129de2
--- /dev/null
+++ b/helloworld/H2_E2.c
@@ -0,0 +1,8 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+void main() {
+	printf("It's fun to write my own program in C.\n");
+	exit(0);
+	
+}
\ No newline at end of file
diff --git a/helloworld/H2_E3.c b/helloworld/H2_E3.c
new file mode 100644
index 0000000..256ecd2
--- /dev/null
+++ b/helloworld/H2_E3.c
@@ -0,0 +1,7 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+void main() {
+	printf("\nHowdy, neighbor!\nThis is my first C program.\n");
+	return 0;
+}
\ No newline at end of file
diff --git a/helloworld/H3_E5.c b/helloworld/H3_E5.c
new file mode 100644
index 0000000..5b97dcf
--- /dev/null
+++ b/helloworld/H3_E5.c
@@ -0,0 +1,10 @@
+#include <stdio.h>
+/* This function multiplicate two integers and returns the result */
+int integer_mult(int x, int y) {
+	return x * y;
+}
+
+int main() {
+	printf("3 times 5 is %d.\n", integer_mult(3, 5));
+	return 0;
+}
\ No newline at end of file
diff --git a/helloworld/H4_E1.c b/helloworld/H4_E1.c
new file mode 100644
index 0000000..ade56cb
--- /dev/null
+++ b/helloworld/H4_E1.c
@@ -0,0 +1,6 @@
+#include <stdio.h>
+
+int main() {
+	printf("The numeric value of Z is: %d, the same of z is: %d.", 'Z', 'z');
+	return 0;
+}
\ No newline at end of file
diff --git a/helloworld/H4_E2.c b/helloworld/H4_E2.c
new file mode 100644
index 0000000..a131fd0
--- /dev/null
+++ b/helloworld/H4_E2.c
@@ -0,0 +1,6 @@
+#include <stdio.h>
+
+int main() {
+	printf("The ASCII value of 72 is character: %c, the 104 is character: %c.", 72, 104);
+	return 0;
+}
\ No newline at end of file
diff --git a/helloworld/H4_E4.c b/helloworld/H4_E4.c
new file mode 100644
index 0000000..8ec0ebb
--- /dev/null
+++ b/helloworld/H4_E4.c
@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+int main() {
+	double dbl_num = 123.456;
+	printf("Floating is: %f, scientific is: %e.", dbl_num, dbl_num);
+	return 0;
+}
\ No newline at end of file
diff --git a/helloworld/H4_E5.c b/helloworld/H4_E5.c
new file mode 100644
index 0000000..7c4986c
--- /dev/null
+++ b/helloworld/H4_E5.c
@@ -0,0 +1,6 @@
+#include <stdio.h>
+
+int main() {
+	printf("The numeric value of '\n' is: %d.", '\n');
+	return 0;
+}
\ No newline at end of file
diff --git a/helloworld/H5_E1.c b/helloworld/H5_E1.c
new file mode 100644
index 0000000..9ee1565
--- /dev/null
+++ b/helloworld/H5_E1.c
@@ -0,0 +1,33 @@
+#include <stdio.h>
+
+int main() {
+	//1. feladat
+	printf("%c%c%c\n", 'B', 'y', 'e');
+	//2. feladat
+	int number1 = 123;
+	float number2 = 123.456;
+	printf("%d\n%f\n", number1, number2);
+	printf("%-8d\n%-8f\n", number1, number2);
+	//3. feladat
+	int number3 = -15;
+	int number4 = 150;
+	int number5 = 1500;
+	printf(
+		"-15 hexadecimális formában: %x,\n 150 hexadecimális alakja: %x,\n1500 hexadecimális alakja: %x\n",
+		number3,
+		number4,
+		number5
+	);
+	//4. feladat
+	int ch;
+	setbuf(stdout, NULL);
+	printf("Please type in one character:\n");
+	ch = getchar();
+	printf("The character you just entered is:\n");
+	putchar (ch);
+	
+	return 0;
+}
+
+//5. feladat
+// the header stdio.h is missing
\ No newline at end of file
diff --git a/helloworld/H6_E1.c b/helloworld/H6_E1.c
new file mode 100644
index 0000000..c4f8679
--- /dev/null
+++ b/helloworld/H6_E1.c
@@ -0,0 +1,51 @@
+#include <stdio.h>
+
+int main() {
+	//1. feladat
+	//Given x = 1 and y = 3, write a program to print 
+	//out the results of these expressions: x += y, 
+	//x += -y, x -= y, x -= -y, x *= y, and x *= -y.
+	int x = 1;
+	int y = 3;
+	printf("x += y értéke:%d\n", x += y);
+	x = 1;
+	printf("x += -y értéke:%d\n", x += (-y));
+	x = 1;
+	printf("x -= y értéke:%d\n", x -= y);
+	x = 1;
+	printf("x -= -y értéke:%d\n", x -= (-y));
+	x = 1;
+	printf("x *= y értéke:%d\n", x *= y);
+	x = 1;
+	printf("x *= -y értéke:%d\n", x *= (-y));
+
+	//2. feladat
+	//Given x = 3 and y = 6, what is the value of z after the expression
+	//z = x * y == 18 is executed?
+	// answer is '1'
+	
+	//3. feladat
+	x = 1;
+	printf("x++ produces:   %d\n", x++);
+	printf("Now x contains: %d\n", x);
+	
+	//4. feladat
+	x = 1;
+	printf("x = x++ produces: %d\n", x = x++);
+	printf("Now x contains:   %d\n", x);
+	// x returns 1, bec x=x++ means: x++ returns 1
+
+	return 0;
+}
+
+/*5. feladat
+#include <stdio.h>
+main()
+{
+   int x, y;
+   x = y = 0;
+   printf("The comparison result is: %d\n",  x = y); [x==y is the proper comparison]
+   return 0;
+}
+*/
+//setbuf(stdout, NULL);
\ No newline at end of file
diff --git a/helloworld/H7_E1.c b/helloworld/H7_E1.c
new file mode 100644
index 0000000..d26437a
--- /dev/null
+++ b/helloworld/H7_E1.c
@@ -0,0 +1,71 @@
+#include <stdio.h>
+
+int main() {
+	//1.-2. feladat
+	//What is the difference between 
+	//the following two pieces of code?
+	// for (i=0, j=1; i<8; i++, j++)
+	// printf("%d  +  %d  =  %d\n", i, j, i+j);
+	//
+	//for (i=0, j=1; i<8; i++, j++);
+	//printf("%d  +  %d  =  %d\n", i, j, i+j);
+	
+	//in the line 11 there is an "empty" loop, it does not anyting 
+	
+	//2. feladat
+	//Write a program that contains the two pieces of 
+	//code shown in exercise 1, and then execute the program. 
+	//What are you going to see on the screen?
+	int i;
+	int j;
+	printf("2. feladat\n");
+	for (i = 0, j = 1; i < 8; i++, j++)
+		printf("%d + %d = %d\n", i, j, i+j);
+	
+	
+	for (i = 0, j = 1; i < 8; i++, j++);
+		printf("%d + %d = %d\n", i, j, i+j);
+	//the 2. loop doesn't do anything
+	
+	//3. feladat
+	//Rewrite the program in Listing 7.4. This time,
+	//you want the for statement to keep looping until
+	//the user enters the character K.
+	int c;
+	setbuf(stdout, NULL);
+	printf("\n3. feladat\n");
+	printf("Enter a character:\n(enter K to exit)\n");
+	c = ' ';
+	while (c = getc(stdin) != 'K') {
+		putchar(c);
+	}
+	printf("\nOut of the for loop. Bye!\n");
+	
+	
+	//4. feladat
+	//Rewrite the program in Listing 7.6 by replacing 
+	//the do-while loop with a for loop.
+	printf("\n4. feladat\n");
+	for (i = 65; i < 72; i++) {
+		printf("The numeric value of %c is %d.\n", i, i);
+	}
+	
+	//5. feladat
+	//Rewrite the program in Listing 7.7. 
+	//This time, use a while loop as the outer loop 
+	//and a do-while loop as the inner loop.
+	i = 1;
+	printf("\n5. feladat\n");
+	while (i <= 3) {   // outer loop 
+		printf("The start of iteration %d of the outer loop.\n", i);
+		j = 1;
+		do {
+			printf("    Iteration %d of the inner loop.\n", j);
+			j++;
+		} while (j <= 4);
+		printf("The end of iteration %d of the outer loop.\n", i);
+		i++;
+	}
+	return 0;
+}
+
diff --git a/helloworld/ascii_bitwise.c b/helloworld/ascii_bitwise.c
new file mode 100644
index 0000000..c9db2a7
--- /dev/null
+++ b/helloworld/ascii_bitwise.c
@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+int main(){
+	//printf("%c%c%c\n",'B'^0b00100000, 'y'^0b00100000, 'e'^0b00100000);
+	puts("%c%c%c\n", 'e');
+	return 0;
+}
\ No newline at end of file
diff --git a/helloworld/xpp.c b/helloworld/xpp.c
new file mode 100644
index 0000000..111d02c
--- /dev/null
+++ b/helloworld/xpp.c
@@ -0,0 +1,27 @@
+#include <stdio.h>
+
+int main()
+{
+	int x = 1;
+	printf("x = x + 1 értéke:%d\n",x = x + 1);
+	printf("Now x contains: %d\n", x);
+
+	x = 1;
+	printf("x++ produces:   %d\n", x++);
+	printf("Now x contains: %d\n", x);
+
+
+	return 0;
+}
+
+/*5. feladat
+#include <stdio.h>
+main()
+{
+   int x, y;
+   x = y = 0;
+   printf("The comparison result is: %d\n",  x = y); [x==y is the proper comparison]
+   return 0;
+}
+*/
+//setbuf(stdout, NULL);
\ No newline at end of file