diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ce94c57
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,61 @@
+# Created by https://www.toptal.com/developers/gitignore/api/c
+# Edit at https://www.toptal.com/developers/gitignore?templates=c
+
+### C ###
+# Prerequisites
+*.d
+
+# Object files
+*.o
+*.ko
+*.obj
+*.elf
+
+# Linker output
+*.ilk
+*.map
+*.exp
+
+# Precompiled Headers
+*.gch
+*.pch
+
+# Libraries
+*.lib
+*.a
+*.la
+*.lo
+
+# Shared objects (inc. Windows DLLs)
+*.dll
+*.so
+*.so.*
+*.dylib
+
+# Executables
+*.exe
+*.out
+*.app
+*.i*86
+*.x86_64
+*.hex
+
+# Debug files
+*.dSYM/
+*.su
+*.idb
+*.pdb
+
+# Kernel Module Compile Results
+*.mod*
+*.cmd
+.tmp_versions/
+modules.order
+Module.symvers
+Mkfile.old
+dkms.conf
+
+# User specific
+/kernel-sign
+
+# End of https://www.toptal.com/developers/gitignore/api/c
diff --git a/bitmap.c b/bitmap.c
new file mode 100644
index 0000000..c738724
--- /dev/null
+++ b/bitmap.c
@@ -0,0 +1,85 @@
+#include "bitmap.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+#ifdef bitmap_64
+#define bitmap_type unsigned long long int
+#define bitmap_shift 6
+#define bitmap_mask 63
+#define bitmap_wordlength 64
+#define bitmap_fmt "%016llx"
+#else // assumed to be 32 bits
+#define bitmap_type unsigned int
+#define bitmap_shift 5
+#define bitmap_mask 31
+#define bitmap_wordlength 32
+#define bitmap_fmt "%08x"
+#endif
+
+// get the types right
+#define bitmap_one (bitmap_type)1
+
+// we expect 0 <= n and n < b->bits, but it is not verified
+
+// arch a 8 bit
+// bitmap shift 3
+// wordlength 8
+
+// n = 10 -> 00001010
+// 00000001 -> word = 1
+//
+// n = 12 ->   00001100
+// mask = 7 -> 00000111
+//             00000100 = 4
+// 00000001 -> word = 1
+//
+// n = 32 ->    00100000
+// mask = 7 ->  00000111
+// 00000000
+// 00000100 -> word = 4
+//
+// n = 127 ->      01111111
+// mask = 7 ->     00000111
+// position = 7 -> 00000111
+//
+
+void bitmap_set(bitmap *b, int n) {
+  int word = n >> bitmap_shift;   // n / bitmap_wordlength
+  int position = n & bitmap_mask; // n % bitmap_wordlength
+  b->array[word] |= bitmap_one << position;
+}
+
+void bitmap_clear(bitmap *b, int n) {
+  int word = n >> bitmap_shift;   // n / bitmap_wordlength
+  int position = n & bitmap_mask; // n % bitmap_wordlength
+  b->array[word] &= ~(bitmap_one << position);
+}
+
+int bitmap_read(bitmap *b, int n) {
+  int word = n >> bitmap_shift;   // n / bitmap_wordlength
+  int position = n & bitmap_mask; // n % bitmap_wordlength
+  return (b->array[word] >> position) & 1;
+}
+
+bitmap *bitmap_allocate(int bits) {
+  // error-checking should be better :-)
+  bitmap *b = malloc(sizeof(bitmap));
+  b->bits = bits;
+  b->words = (bits + bitmap_wordlength - 1) / bitmap_wordlength;
+  // divide, but round up for the ceiling
+  b->array = calloc(b->words, sizeof(bitmap_type));
+  return b;
+}
+
+void bitmap_deallocate(bitmap *b) {
+  // error-checking should be better :-)
+  free(b->array);
+  free(b);
+}
+
+void bitmap_print(bitmap *b) {
+  for (int i = 0; i < b->words; i++) {
+    printf(" " bitmap_fmt, b->array[i]);
+  }
+  printf("\n");
+}
diff --git a/bitmap.h b/bitmap.h
new file mode 100644
index 0000000..7b4d45d
--- /dev/null
+++ b/bitmap.h
@@ -0,0 +1,22 @@
+// use dynamic allocation with these functions
+// compile with -Dbitmap_64 to force 64-bit words
+// compile with -O [dash capital o] for more efficient machine code
+
+#ifdef bitmap_64
+#define bitmap_type unsigned long long int
+#else // assumed to be 32 bits
+#define bitmap_type unsigned int
+#endif
+
+typedef struct {
+  int bits;  // number of bits in the array
+  int words; // number of words in the array
+  bitmap_type *array;
+} bitmap;
+
+void bitmap_set(bitmap *b, int n); // n is a bit index
+void bitmap_clear(bitmap *b, int n);
+int bitmap_read(bitmap *b, int n);
+bitmap *bitmap_allocate(int bits);
+void bitmap_deallocate(bitmap *b);
+void bitmap_print(bitmap *b);
diff --git a/collatz.c b/collatz.c
new file mode 100644
index 0000000..d04276b
--- /dev/null
+++ b/collatz.c
@@ -0,0 +1,54 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+int collatz(int, int[], int);
+void print_buffer(int buff[]);
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    perror("Usage: collatz NUMBER\n");
+    return EXIT_FAILURE;
+  }
+
+  int n = atoi(argv[1]);
+  if (n <= 1) {
+    perror("The number MUST be greater than 1\n");
+    return EXIT_FAILURE;
+  }
+
+  printf("Collatz of %d\n", n);
+
+  pid_t pid = fork();
+  if (pid == 0) {
+    int buff[1024] = {0};
+    collatz(n, buff, 0);
+    print_buffer(buff);
+  } else if (pid > 0) {
+    wait(NULL);
+  }
+
+  return EXIT_SUCCESS;
+}
+
+int collatz(int n, int buff[], int steps) {
+  buff[steps] = n;
+  if (n == 1) {
+    return n;
+  } else if (n % 2 == 0) {
+    return collatz(n / 2, buff, steps + 1);
+  } else {
+    return collatz(3 * n + 1, buff, steps + 1);
+  }
+}
+
+void print_buffer(int buff[]) {
+  int i = 0;
+  while (buff[i] != 0) {
+    printf("%d ", buff[i]);
+    i++;
+  }
+  printf("\n");
+}
diff --git a/collatz_shm.c b/collatz_shm.c
new file mode 100644
index 0000000..0528c72
--- /dev/null
+++ b/collatz_shm.c
@@ -0,0 +1,64 @@
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#define SIZE 4096
+#define SHM_NAME "collatz"
+
+int collatz(int, void *);
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    perror("Usage: collatz NUMBER\n");
+    return EXIT_FAILURE;
+  }
+
+  int n = atoi(argv[1]);
+  if (n <= 1) {
+    perror("The number MUST be greater than 1\n");
+    return EXIT_FAILURE;
+  }
+
+  printf("Collatz of %d\n", n);
+
+  // Create memory shared object
+  int fd = shm_open(SHM_NAME, O_CREAT | O_RDWR, 0600);
+  ftruncate(fd, SIZE);
+  void *ptr = (int *)mmap(0, SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+
+  pid_t pid = fork();
+  if (pid == 0) {
+    collatz(n, ptr);
+  } else if (pid > 0) {
+    wait(NULL);
+
+    printf("%s\n", (char *)ptr);
+    shm_unlink(SHM_NAME);
+  }
+
+  return EXIT_SUCCESS;
+}
+
+int collatz(int n, void *shm) {
+  char buff[50];
+  sprintf(buff, "%d", n);
+  sprintf(shm, "%s", buff);
+  shm += strlen(buff);
+
+  sprintf(shm, "%s", " ");
+  shm += 1;
+
+  if (n == 1) {
+    return n;
+  } else if (n % 2 == 0) {
+    return collatz(n / 2, shm);
+  } else {
+    return collatz(3 * n + 1, shm);
+  }
+}
diff --git a/collatz_shm2.c b/collatz_shm2.c
new file mode 100644
index 0000000..dfef3ef
--- /dev/null
+++ b/collatz_shm2.c
@@ -0,0 +1,60 @@
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+int collatz(int, int *, int);
+void print_buffer(int buff[]);
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    perror("Usage: collatz NUMBER\n");
+    return EXIT_FAILURE;
+  }
+
+  int n = atoi(argv[1]);
+  if (n <= 1) {
+    perror("The number MUST be greater than 1\n");
+    return EXIT_FAILURE;
+  }
+
+  printf("Collatz of %d\n", n);
+
+  int *buff = mmap(NULL, sizeof(int *) * 1024, PROT_READ | PROT_WRITE,
+                   MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+
+  pid_t pid = fork();
+  if (pid == 0) {
+    collatz(n, buff, 0);
+  } else if (pid > 0) {
+    wait(NULL);
+    print_buffer(buff);
+  }
+
+  return EXIT_SUCCESS;
+}
+
+int collatz(int n, int *shm, int steps) {
+  *(shm + steps) = n;
+  if (n == 1) {
+    return n;
+  } else if (n % 2 == 0) {
+    return collatz(n / 2, shm, steps + 1);
+  } else {
+    return collatz(3 * n + 1, shm, steps + 1);
+  }
+}
+
+void print_buffer(int buff[]) {
+  int i = 0;
+  while (buff[i] != 0) {
+    printf("%d ", buff[i]);
+    i++;
+  }
+  printf("\n");
+}
diff --git a/cons.c b/cons.c
new file mode 100644
index 0000000..409b1b8
--- /dev/null
+++ b/cons.c
@@ -0,0 +1,21 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/shm.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+
+int main()
+{
+  const int SIZE = 4096;
+  const char *name = "OS";
+
+  int shm_fd;
+  void *ptr;
+
+  shm_fd = shm_open(name, O_RDONLY, 0666);
+  ptr = mmap(0, SIZE, PROT_READ, MAP_SHARED, shm_fd, 0);
+  printf("%s", (char *)ptr);
+  shm_unlink(name);
+}
diff --git a/ex1.c b/ex1.c
new file mode 100644
index 0000000..9015b9c
--- /dev/null
+++ b/ex1.c
@@ -0,0 +1,46 @@
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+
+struct MyStruct {
+  int value;
+};
+
+int value = 5;
+
+int main(void)
+{
+  struct MyStruct *str;
+  str->value = 5;
+
+  int *p = malloc(sizeof(int));
+  *p = 100;
+
+  printf("PARENT: %p\n", &value);
+  printf("PARENT: %p\n", str);
+  printf("PARENT: %p\n", p);
+
+  pid_t pid;
+  pid = fork();
+
+  if (pid == 0) {
+    value += 15;
+    str->value += 15;
+    *p += 10;
+    printf("CHILD: %p, %d\n", &value, value);
+    printf("CHILD: %p, %d\n", &str->value, str->value);
+    printf("CHILD: %p, %d\n", p, *p);
+    return 0;
+  } else if (pid > 0) {
+    wait(NULL);
+    printf("PARENT: value = %d\n", value);
+    printf("PARENT: value = %d\n", str->value);
+    printf("PARENT: value = %d\n", *p);
+
+    free(p);
+
+    return 0;
+  }
+}
diff --git a/ex12.c b/ex12.c
new file mode 100644
index 0000000..96a6ea3
--- /dev/null
+++ b/ex12.c
@@ -0,0 +1,39 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+void add_children(pid_t children[], pid_t pid);
+
+int main(void) 
+{
+  pid_t parent_pid = getpid();
+  pid_t children[1024] = {-1};
+  for (int i = 0; i < 4; i++) {
+    pid_t pid = fork();
+    add_children(children, pid);
+  }
+
+  if (parent_pid = getpid()) {
+    wait(NULL);
+    printf("pids: ");
+    for (int i = 0; i < 1024; i++) {
+      if (children[i] == -1) {
+        printf("\n");
+        break;
+      }
+      printf("%d ", children[i]);
+    }
+  }
+
+  return 0;
+}
+
+void add_children(pid_t children[], pid_t pid)
+{
+  for (int i = 0; i < 1024; i++) {
+    if (children[i] < 0) {
+      children[i] = pid;
+      break;
+    }
+  }
+}
diff --git a/ex13.c b/ex13.c
new file mode 100644
index 0000000..25d804a
--- /dev/null
+++ b/ex13.c
@@ -0,0 +1,23 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+int main(void)
+{
+  pid_t pid;
+  pid = fork();
+
+  if (pid < 0) {
+    fprintf(stderr, "Fork failed\n");
+    return 1;
+  } else if (pid == 0) {
+    execlp("/bin/ls", "ls", NULL);
+    printf("LINEA J\n");
+  } else {
+    wait(NULL);
+    printf("Child complete\n");
+  }
+
+  return 0;
+}
diff --git a/ex14.c b/ex14.c
new file mode 100644
index 0000000..2e10389
--- /dev/null
+++ b/ex14.c
@@ -0,0 +1,27 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+int main(void) {
+  pid_t pid, pid1;
+
+  pid = fork();
+
+  if (pid < 0) {
+    fprintf(stderr, "Fork failed");
+    return EXIT_FAILURE;
+  } else if (pid == 0) {
+    pid1 = getpid();
+    printf("child: pid = %d\n", pid);   // A
+    printf("child: pid1 = %d\n", pid1); // B
+  } else {
+    pid1 = getpid();
+    printf("parent: pid = %d\n", pid);   // C
+    printf("parent: pid1 = %d\n", pid1); // D
+    wait(NULL);
+  }
+
+  return EXIT_SUCCESS;
+}
diff --git a/ex17.c b/ex17.c
new file mode 100644
index 0000000..4e0d87d
--- /dev/null
+++ b/ex17.c
@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#define SIZE 5
+
+int nums[SIZE] = {0, 1, 2, 3, 4};
+
+int main(void) {
+  int i;
+  pid_t pid;
+
+  pid = fork();
+
+  if (pid == 0) {
+    for (i = 0; i < SIZE; i++) {
+      nums[i] *= -i;
+      printf("CHILD : %d\n", nums[i]); // Linea X
+    }
+  } else if (pid > 0) {
+    wait(NULL);
+    for (i = 0; i < SIZE; i++) {
+      printf("PARENT: %d\n", nums[i]); // Linea Y
+    }
+  }
+
+  return EXIT_SUCCESS;
+}
diff --git a/ex19.c b/ex19.c
new file mode 100644
index 0000000..6def429
--- /dev/null
+++ b/ex19.c
@@ -0,0 +1,18 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+int main(void) {
+  pid_t parent_pid = getpid();
+  pid_t pid = fork();
+
+  if (pid > 0) {
+    printf("PARENT PID = %d, CHILD PID = %d\n", parent_pid, pid);
+    sleep(10);
+    wait(NULL);
+  }
+
+  return EXIT_SUCCESS;
+}
diff --git a/pid_manager.c b/pid_manager.c
new file mode 100644
index 0000000..bd21294
--- /dev/null
+++ b/pid_manager.c
@@ -0,0 +1,63 @@
+#include "pid_manager.h"
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define MIN_PID 300
+#define MAX_PID 5000
+#define SIZE (MAX_PID - MIN_PID + 1)
+
+bool pids[SIZE];
+
+int allocate_map(void) {
+  for (int i = 0; i < SIZE; i++) {
+    pids[i] = false;
+  }
+  return 1;
+}
+
+int allocate_pid(void) {
+  for (int i = 0; i < SIZE; i++) {
+    if (!pids[i]) {
+      pids[i] = true;
+      return i + MIN_PID;
+    }
+  }
+  return -1;
+}
+
+void release_pid(int pid) {
+  if (pid >= MIN_PID && pid <= MAX_PID) {
+    pids[pid - MIN_PID] = false;
+  }
+}
+
+int main(void) {
+  if (allocate_map() != 1) {
+    perror("Failed to initialiaze PID Manager\n");
+    exit(1);
+  }
+
+  for (int i = 0; i < SIZE; i++) {
+    printf("Allocate PID = %d\n", allocate_pid());
+  }
+
+  int last = allocate_pid();
+  printf("Attempt to allocate another PID, result %d\n", last);
+
+  if (last == -1) {
+    printf("Release a PID 4000\n");
+    release_pid(4000);
+  }
+
+  printf("Allocate another PID: %d\n", allocate_pid());
+
+  printf("Release PIDs 300 and 5000\n");
+  release_pid(300);
+  release_pid(5000);
+
+  printf("Allocate another PID: %d\n", allocate_pid());
+  printf("Allocate another PID: %d\n", allocate_pid());
+
+  return 0;
+}
diff --git a/pid_manager.h b/pid_manager.h
new file mode 100644
index 0000000..a8011f8
--- /dev/null
+++ b/pid_manager.h
@@ -0,0 +1,15 @@
+#if !defined(__PID_MANGER_H__)
+#define __PID_MANGER_H__
+
+// Crea e inizializza una struttura per rappresentare i pid;
+// restituisce -1 in caso di insuccesso e 1 in caso di successo.
+int allocate_map(void);
+
+// Alloca e restituisce un pid, restituisce -1 se non è possibile
+// assegnare un PID (tutti i pid sono in uso).
+int allocate_pid(void);
+
+// Rilascia un pid
+void release_pid(int pid);
+
+#endif
diff --git a/prod.c b/prod.c
new file mode 100644
index 0000000..181a349
--- /dev/null
+++ b/prod.c
@@ -0,0 +1,31 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/shm.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+
+int main()
+{
+  const int SIZE = 4096;
+  const char *name = "OS";
+  const char *message_0 = "Hello";
+  const char *message_1 = "World!";
+
+  int shm_fd;
+  void *ptr;
+
+  shm_fd = shm_open(name, O_CREAT | O_RDWR, 0666);
+  ftruncate(shm_fd, SIZE);
+  ptr = mmap(0, SIZE, PROT_WRITE, MAP_SHARED, shm_fd, 0);
+  sprintf(ptr, "%s", message_0);
+  ptr += strlen(message_0);
+  sprintf(ptr, "%s", " ");
+  ptr += 1;
+  sprintf(ptr, "%s", message_1);
+  ptr += strlen(message_1);
+
+  return 0;
+}
diff --git a/test.c b/test.c
new file mode 100644
index 0000000..8ec4683
--- /dev/null
+++ b/test.c
@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+int main(void) {
+  int n;
+  printf("%d\n", n);
+  return 0;
+}