diff --git a/20211004/calc-1.c b/20211004/calc-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..cf2a21d8fccc2150610486374efa0d8c0606240d
--- /dev/null
+++ b/20211004/calc-1.c
@@ -0,0 +1,11 @@
+#include <stdio.h>
+
+int main (void)
+{
+  double a;
+  printf ("Bitte eine Zahl eingeben: ");
+  scanf ("%lf", &a);
+  a = 2 * a;
+  printf ("Das Doppelte ist: %lf\n", a);
+  return 0;
+}
diff --git a/20211004/if-1.c b/20211004/if-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..46b7ae90c99a56eec699546056c4ffdc68f2cb96
--- /dev/null
+++ b/20211004/if-1.c
@@ -0,0 +1,10 @@
+#include <stdio.h>
+
+int main (void)
+{
+  int a, b;
+  printf ("Bitte zwei Zahlen eingeben: ");
+  scanf ("%d,%d", &a, &b);
+  printf ("%d / %d = %d\n", a, b, a / b);
+  return 0;
+}
diff --git a/20211004/if-2.c b/20211004/if-2.c
new file mode 100644
index 0000000000000000000000000000000000000000..7682105612bc0dbf9b7bb9eca1e1d4df5b0c4245
--- /dev/null
+++ b/20211004/if-2.c
@@ -0,0 +1,11 @@
+#include <stdio.h>
+
+int main (void)
+{
+  int a, b;
+  printf ("Bitte zwei Zahlen eingeben: ");
+  scanf ("%d,%d", &a, &b);
+  if (b != 0)
+    printf ("%d / %d = %d\n", a, b, a / b);
+  return 0;
+}
diff --git a/20211004/if-3.c b/20211004/if-3.c
new file mode 100644
index 0000000000000000000000000000000000000000..0009807adb825f737650a83a15e605dece1ac0b8
--- /dev/null
+++ b/20211004/if-3.c
@@ -0,0 +1,13 @@
+#include <stdio.h>
+
+int main (void)
+{
+  int a, b;
+  printf ("Bitte zwei Zahlen eingeben: ");
+  scanf ("%d,%d", &a, &b);
+  if (b != 0)
+    printf ("%d / %d = %d\n", a, b, a / b);
+  else
+    printf ("Bitte nicht durch 0 dividieren.\n");
+  return 0;
+}
diff --git a/20211004/if-4.c b/20211004/if-4.c
new file mode 100644
index 0000000000000000000000000000000000000000..7d66b3f2572c2c3fde9740dfb7bf573cb6fde482
--- /dev/null
+++ b/20211004/if-4.c
@@ -0,0 +1,14 @@
+#include <stdio.h>
+
+int main (void)
+{
+  int a, b;
+  printf ("Bitte zwei Zahlen eingeben: ");
+  scanf ("%d,%d", &a, &b);
+  if (b != 0)
+    printf ("%d / %d = %d\n", a, b, a / b);
+  else
+    printf ("Bitte nicht durch 0 dividieren.\n");
+    printf ("Das tut man nicht.\n");
+  return 0;
+}
diff --git a/20211004/if-5.c b/20211004/if-5.c
new file mode 100644
index 0000000000000000000000000000000000000000..af2281a56b7c6c8f0a37c5b96bc13d885d3eb8fc
--- /dev/null
+++ b/20211004/if-5.c
@@ -0,0 +1,16 @@
+#include <stdio.h>
+
+int main (void)
+{
+  int a, b;
+  printf ("Bitte zwei Zahlen eingeben: ");
+  scanf ("%d,%d", &a, &b);
+  if (b != 0)
+    printf ("%d / %d = %d\n", a, b, a / b);
+  else
+    {
+      printf ("Bitte nicht durch 0 dividieren.\n");
+      printf ("Das tut man nicht.\n");
+    }
+  return 0;
+}
diff --git a/20211004/if-6.c b/20211004/if-6.c
new file mode 100644
index 0000000000000000000000000000000000000000..b06e1a52fff0766dc930e19f7ff2ebc4818849de
--- /dev/null
+++ b/20211004/if-6.c
@@ -0,0 +1,14 @@
+#include <stdio.h>
+
+int main (void) {
+    int a, b;
+    printf ("Bitte zwei Zahlen eingeben: ");
+    scanf ("%d,%d", &a, &b);
+    if (b != 0) {
+        printf ("%d / %d = %d\n", a, b, a / b);
+    } else {
+        printf ("Bitte nicht durch 0 dividieren.\n");
+        printf ("Das tut man nicht.\n");
+    }
+    return 0;
+}
diff --git a/20211004/if-7.c b/20211004/if-7.c
new file mode 100644
index 0000000000000000000000000000000000000000..a355cd19a1a302b95a89a48f18d4369e2a7d5fe5
--- /dev/null
+++ b/20211004/if-7.c
@@ -0,0 +1,5 @@
+#include <stdio.h>
+int main (void) { int a, b; printf ("Bitte zwei Zahlen eingeben: "); scanf
+("%d,%d", &a, &b); if (b != 0) { printf ("%d / %d = %d\n", a, b, a / b); } else
+{ printf ("Bitte nicht durch 0 dividieren.\n"); printf ("Das tut man
+nicht.\n"); } return 0; }
diff --git a/20211004/if-8.c b/20211004/if-8.c
new file mode 100644
index 0000000000000000000000000000000000000000..14c135cd0f431ed1c667a844cc9ae27510e9e653
--- /dev/null
+++ b/20211004/if-8.c
@@ -0,0 +1,5 @@
+#include <stdio.h>
+int main (void) { int a, b; printf ("Bitte zwei Zahlen eingeben: "); scanf
+("%d,%d", &a, &b); if (b != 0) { printf ("%d / %d = %d\n", a, b, a / b); } else
+{ printf ("Bitte nicht durch 0 dividieren.\n"); printf (
+"Das tut man nicht.\n"); } return 0; }
diff --git a/20211004/if-9.c b/20211004/if-9.c
new file mode 100644
index 0000000000000000000000000000000000000000..7fcbc6a4003ed963bfd862956bb1105a39b632fa
--- /dev/null
+++ b/20211004/if-9.c
@@ -0,0 +1,16 @@
+#include <stdio.h>
+
+int main (void)
+{
+  int a, b;
+  printf ("Bitte zwei Zahlen eingeben: ");
+  scanf ("%d,%d", &a, &b);
+  if (b)
+    printf ("%d / %d = %d\n", a, b, a / b);
+  else
+    {
+      printf ("Bitte nicht durch 0 dividieren.\n");
+      printf ("Das tut man nicht.\n");
+    }
+  return 0;
+}
diff --git a/20211004/init-1.c b/20211004/init-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..8aa071ef255eb900d4184747f6ed04c42458ee6e
--- /dev/null
+++ b/20211004/init-1.c
@@ -0,0 +1,10 @@
+#include <stdio.h>
+
+int main (void)
+{
+  int a = 42;
+  printf ("a = ", a, "\n");
+  a = 137;
+  printf ("a = ", a, "\n");
+  return 0;
+}
diff --git a/20211004/init-2.c b/20211004/init-2.c
new file mode 100644
index 0000000000000000000000000000000000000000..40f5513ecab3921b61c70034fcd06b27e14548dd
--- /dev/null
+++ b/20211004/init-2.c
@@ -0,0 +1,10 @@
+#include <stdio.h>
+
+int main (void)
+{
+  int a = 42;
+  printf ("a = %d\n", a);
+  a = 137;
+  printf ("a = %d\n", a);
+  return 0;
+}
diff --git a/20211004/loops-1.c b/20211004/loops-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..68495de22f28c376a7080bcbcb943feece6f6bf2
--- /dev/null
+++ b/20211004/loops-1.c
@@ -0,0 +1,13 @@
+#include <stdio.h>
+
+int main (void)
+{
+  int a;
+  a = 1;
+  while (a <= 10)
+    {
+      printf ("%dn", a);
+      a = a + 1;
+    }
+  return 0;
+}
diff --git a/20211004/loops-2.c b/20211004/loops-2.c
new file mode 100644
index 0000000000000000000000000000000000000000..84912102488878cd3ad2ee11cf84551de8403fc1
--- /dev/null
+++ b/20211004/loops-2.c
@@ -0,0 +1,13 @@
+#include <stdio.h>
+
+int main (void)
+{
+  int a;
+  a = 1;
+  while (a <= 10)
+    {
+      printf ("%d\n", a);
+      a = a + 1;
+    }
+  return 0;
+}
diff --git a/20211004/loops-3.c b/20211004/loops-3.c
new file mode 100644
index 0000000000000000000000000000000000000000..ebaed116f8fba5efaca85765f5baf8393aff6109
--- /dev/null
+++ b/20211004/loops-3.c
@@ -0,0 +1,12 @@
+#include <stdio.h>
+
+int main (void)
+{
+  int a = 1;
+  while (a <= 10)
+    {
+      printf ("%d\n", a);
+      a++;
+    }
+  return 0;
+}
diff --git a/20211004/loops-4.c b/20211004/loops-4.c
new file mode 100644
index 0000000000000000000000000000000000000000..ab32889936d61b2fdaec641cf8ea453c4ca27711
--- /dev/null
+++ b/20211004/loops-4.c
@@ -0,0 +1,9 @@
+#include <stdio.h>
+
+int main (void)
+{
+  int a = 1;
+  while (a <= 10)
+    printf ("%d\n", a++);
+  return 0;
+}
diff --git a/20211004/loops-5.c b/20211004/loops-5.c
new file mode 100644
index 0000000000000000000000000000000000000000..2c95b8c2bad694e41be5b6bb2b6606395c34af60
--- /dev/null
+++ b/20211004/loops-5.c
@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+int main (void)
+{
+  for (int a = 1; a <= 10; a++)
+    printf ("%d\n", a);
+  return 0;
+}
diff --git a/20211004/loops-6.c b/20211004/loops-6.c
new file mode 100644
index 0000000000000000000000000000000000000000..eb77790700657077a683f33d339f42f26982a1b2
--- /dev/null
+++ b/20211004/loops-6.c
@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+int main (void)
+{
+  for (int a = 1; a <= 10; printf ("%d\n", a++));
+  return 0;
+}
diff --git a/20211004/loops-7.c b/20211004/loops-7.c
new file mode 100644
index 0000000000000000000000000000000000000000..ca6f03726df50540e22eeacdbedd466efaf0e5c6
--- /dev/null
+++ b/20211004/loops-7.c
@@ -0,0 +1,13 @@
+#include <stdio.h>
+
+int main (void)
+{
+  int a = 1;
+  do
+    {
+      printf ("%d\n", a);
+      a++;
+    }
+  while (a <= 10);
+  return 0;
+}