diff --git a/c_primer_plus/chapter04/03.c b/c_primer_plus/chapter04/03.c
new file mode 100644
index 0000000..72c388c
--- /dev/null
+++ b/c_primer_plus/chapter04/03.c
@@ -0,0 +1,17 @@
+#include <stdio.h>
+#include <string.h>
+
+
+
+int main (void) {
+
+  float number;
+
+  printf("Give a float number: ");
+  scanf("%g", &number);
+  printf("The input is %.1f or %.1e\n", number, number);
+  printf("The input is %+.3f or %.3e\n", number, number);
+
+  return 0;
+
+}
diff --git a/c_primer_plus/chapter04/04.c b/c_primer_plus/chapter04/04.c
new file mode 100644
index 0000000..7e085c9
--- /dev/null
+++ b/c_primer_plus/chapter04/04.c
@@ -0,0 +1,19 @@
+#include <stdio.h>
+#include <string.h>
+
+
+
+int main (void) {
+
+  float height;
+  char  name[21];
+
+  printf("Give your heigth in cm: ");
+  scanf("%f", &height);
+  printf("Give your name: ");
+  scanf("%20s", name);
+  printf("%s, you are %.3f m tall\n", name, height/100);
+
+  return 0;
+
+}
diff --git a/c_primer_plus/chapter04/05.c b/c_primer_plus/chapter04/05.c
new file mode 100644
index 0000000..94f4e16
--- /dev/null
+++ b/c_primer_plus/chapter04/05.c
@@ -0,0 +1,20 @@
+#include <stdio.h>
+#include <string.h>
+
+
+
+int main (void) {
+
+  float speed;
+  float size;
+
+  printf("Give download speed in Mbit/s: ");
+  scanf("%f", &speed);
+  printf("Give file size in Mbytes: ");
+  scanf("%f", &size);
+  printf("At %.2f megaits per second, a file of %.2f megabytes\n", speed, size);
+  printf("downloads in %.2f seconds\n", size*8/speed);
+
+  return 0;
+
+}
diff --git a/c_primer_plus/chapter04/06.c b/c_primer_plus/chapter04/06.c
new file mode 100644
index 0000000..59e2c6b
--- /dev/null
+++ b/c_primer_plus/chapter04/06.c
@@ -0,0 +1,22 @@
+#include <stdio.h>
+#include <string.h>
+
+
+
+int main (void) {
+
+  char first_name[21];
+  char last_name[21];
+
+  printf("Give your first name: ");
+  scanf("%20s", first_name);
+  printf("Give your last name: ");
+  scanf("%20s", last_name);
+  printf("%s %s\n", first_name, last_name);
+  printf("%*lu %*lu\n", (int)strlen(first_name), strlen(first_name), (int)strlen(last_name), strlen(last_name));
+  printf("%s %s\n", first_name, last_name);
+  printf("%-*lu %-*lu\n", (int)strlen(first_name), strlen(first_name), (int)strlen(last_name), strlen(last_name));
+
+  return 0;
+
+}