Add some theory for pointers

c_modern_approach/Pointers/combining_operatnds.c

@@ -0,0 +1,38 @@
+#include <stdio.h>
+#define ARRAY_SIZE 10
+void print_array(int a[], int array_size) {
+  printf("[");
+  int *p;
+  for (p = a; p < a + array_size; p++) {
+    if (p == &a[array_size - 1]) {
+      printf("%d", *p);
+    } else {
+      printf("%d, ", *p);
+    }
+  }
+  printf("]\n");
+}
+
+int main() {
+  int a[ARRAY_SIZE] = {1, 2, 3, 4, 5, 6, 7, 80, 90, 100};
+  print_array(a, ARRAY_SIZE);
+  printf("*a:\t%d\n", *a);
+  int *ap1 = &a[1];
+  *ap1++ = 99;
+  printf("Executing *ap1++:\n");
+  print_array(a, ARRAY_SIZE);
+  printf("*ap1 after execution:\n");
+  printf("%d\n", *ap1);
+  int *ap2 = &a[2];
+  *(ap2)++ = 88;
+  printf("Executing *(ap2)++:\n");
+  print_array(a, ARRAY_SIZE);
+  printf("*ap2 after execution:\n");
+  printf("%d\n", *ap2);
+  int *ap3 = &a[3];
+  *++ap3 = 77;
+  printf("Executing *++ap3:\n");
+  print_array(a, ARRAY_SIZE);
+  printf("*ap3 after execution:\n");
+  printf("%d\n", *ap3);
+}

c_modern_approach/Pointers/pointers_operands_usage.c

@@ -0,0 +1,18 @@
+#include <stdio.h>
+int main() {
+  int a, *ap;
+  a = 123;
+  ap = &a;
+  int b = 10;
+  printf("a:\t%d\n", a);
+  printf("&a:\t%p\n", &a);
+  printf("ap:\t%p\n", ap);
+  printf("*ap:\t%d\n", *ap);
+  printf("&ap:\t%p\n", &ap);
+  printf("*&ap:\t%p\n", *&ap);
+  printf("**&ap:\t%d\n", **&ap);
+  printf("------\n");
+  printf("b:\t%d\n", b);
+  printf("&b:\t%p\n", &b);
+  printf("*&b:\t%d\n", *&b);
+}

c_modern_approach/Pointers/reverse.c

@@ -0,0 +1,16 @@
+#include <stdio.h>
+#define N 10
+
+int main() {
+  int a[N], *p;
+  printf("Enter %d numbers: ", N);
+  for (p = a; p < a + N; p++) {
+    scanf("%d", p);
+  }
+  printf("In reverse order:");
+  for (p = a + N - 1; p >= a; p--) {
+    printf(" %d", *p);
+  }
+  printf("\n");
+  return 0;
+}