Updated C Pointer Examples.

Senthil Kumaran · Senthil Kumaran · commit a5969dac9206 · 2024-12-01T16:58:50.000Z
diff --git a/source/cprogramming/concepts/cprogs/p10_pointer_to_structures.c b/source/cprogramming/concepts/cprogs/p10_pointer_to_structures.c
@@ -0,0 +1,30 @@
+#include <stdio.h>
+#include <string.h>
+
+struct tag {                     /* the structure type */
+    char lname[20];             /* last name */
+    char fname[20];             /* first name */
+    int age;                    /* age */
+    float rate;                 /* e.g. 12.75 per hour */
+};
+
+struct tag my_struct;           /* define the structure */
+void show_name(struct tag *p);  /* function prototype */
+
+int main(void) {
+    struct tag *st_ptr;         /* a pointer to a structure */
+    st_ptr = &my_struct;        /* point the pointer to my_struct */
+    strcpy(my_struct.lname, "Jensen");
+    strcpy(my_struct.fname, "Ted");
+    printf("\n%s ", my_struct.fname);
+    printf("%s\n", my_struct.lname);
+    my_struct.age = 63;
+    show_name(st_ptr);          /* pass the pointer */
+    return 0;
+}
+
+void show_name(struct tag *p) {
+    printf("\n%s ", p->fname);  /* p points to a structure */
+    printf("%s ", p->lname);
+    printf("%d\n", p->age);
+}
diff --git a/source/cprogramming/concepts/cprogs/p4_pointer.c b/source/cprogramming/concepts/cprogs/p4_pointer.c
@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+int main() {
+    printf("size of a short is %d\\n", sizeof(short));
+    printf("size of a int is %d\\n", sizeof(int));
+    printf("size of a long is %d\\n", sizeof(long));
+}
diff --git a/source/cprogramming/concepts/cprogs/p5_pointer.c b/source/cprogramming/concepts/cprogs/p5_pointer.c
@@ -0,0 +1,17 @@
+#include <stdio.h>
+
+int main(void) {
+
+    int j, k;
+    int *ptr;
+    j = 1;
+    k = 2;
+    ptr = &k;
+    printf("\n");
+    printf("j has the value %d and is stored at %p\n", j, (void *) &j);
+    printf("k has the value %d and is stored at %p\n", k, (void *) &k);
+    printf("ptr has the value %p and is stored at %p\n", ptr, (void *) &ptr);
+    printf("The value of the integer pointed to by ptr is %d\n", *ptr);
+
+    return 0;
+}
diff --git a/source/cprogramming/concepts/cprogs/p6_pointer.c b/source/cprogramming/concepts/cprogs/p6_pointer.c
@@ -0,0 +1,16 @@
+#include <stdio.h>
+
+
+int main(void) {
+
+    int my_array[] = {1, 23, 17, 4, -5, 100};
+    int *ptr;
+    int i;
+    ptr = &my_array[0];
+    printf("\n\n");
+    for (i = 0; i < 6; i++) {
+        printf("my_array[%d] = %d   ", i, my_array[i]);
+        printf("ptr + %d = %d\n", i, *(ptr + i));
+    }
+    return 0;
+}
diff --git a/source/cprogramming/concepts/cprogs/p7_pointer.c b/source/cprogramming/concepts/cprogs/p7_pointer.c
@@ -0,0 +1,22 @@
+#include <stdio.h>
+
+int main(void) {
+
+    char strA[80] = "A string to be used for demonstration purposes";
+    char strB[80];
+
+    char *pA;     /* a pointer to type character */
+    char *pB;     /* another pointer to type character */
+    puts(strA);   /* show string A */
+    pA = strA;    /* point pA at string A */
+    puts(pA);     /* show what pA is pointing to */
+    pB = strB;    /* point pB at string B */
+    putchar('\n');       /* move down one line on the screen */
+    while (*pA != '\0')   /* line A (see text) */
+    {
+        *pB++ = *pA++;   /* line B (see text) */
+    }
+    *pB = '\0';          /* line C (see text) */
+    puts(strB);          /* show strB on screen */
+    return 0;
+}
diff --git a/source/cprogramming/concepts/cprogs/p8_pointer.c b/source/cprogramming/concepts/cprogs/p8_pointer.c
@@ -0,0 +1,24 @@
+#include <stdio.h>
+
+#define ROWS 5
+#define COLS 10
+
+int multi[ROWS][COLS];
+
+int main(void) {
+    int row, col;
+    for (row = 0; row < ROWS; row++) {
+        for (col = 0; col < COLS; col++) {
+            multi[row][col] = row * col;
+        }
+    }
+
+    for (row = 0; row < ROWS; row++) {
+        for (col = 0; col < COLS; col++) {
+            printf("\n%d  ", multi[row][col]);
+            printf("%d ", *(*(multi + row) + col));
+        }
+    }
+
+    return 0;
+}
