Script started on Mon Oct 13 17:19:48 2025
macbook:logs> cd ../programs/C_ch12
macbook:C_ch12> vi pointer_ex1.txt
macbook:C_ch12> cat pointer_ex1.txt 

memory 
address  contents
0000      12
0001      34
...
A120      0     a[0]
A121      1     a[1]   <-- q
A122      2     a[2]
A123      3
A124      4
A125      5            <-- p

p - q = 4

macbook:C_ch12> ls -l | grep "Oct 13"
-rwxr-xr-x  1 mweeks  staff   33560 Oct 13 17:19 a.out
-rw-r--r--  1 mweeks  staff     257 Oct 13 17:15 ch12_4.c
-rw-r--r--  1 mweeks  staff     477 Oct 13 17:19 ch12_starplusplus.c
-rw-r--r--  1 mweeks  staff     193 Oct 13 18:19 pointer_ex1.txt
macbook:C_ch12> cat ch12_starplusplus.c
#include <stdio.h>

int main(){
        int a[8], *p, *q;
        p = &a[0];

        // initialize the array a
        for (int i=0; i<8; i++)
          a[i] = i;
        for (int i=0; i<8; i++) {
          printf("  a[%d] is %d\n", i, a[i]);
        }

        printf("Now change the values \n");
        for (int i=0; i<8; i++) {
          *(p++) *= 3;
        }
        for (int i=0; i<8; i++) {
          printf("  a[%d] is %d\n", i, a[i]);
        }

        return 0;
}
macbook:C_ch12> gcc ch12_starplusplus.c 
macbook:C_ch12> ./a.out
  a[0] is 0
  a[1] is 1
  a[2] is 2
  a[3] is 3
  a[4] is 4
  a[5] is 5
  a[6] is 6
  a[7] is 7
Now change the values 
  a[0] is 0
  a[1] is 3
  a[2] is 6
  a[3] is 9
  a[4] is 12
  a[5] is 15
  a[6] is 18
  a[7] is 21
macbook:C_ch12> cp ch12_starplusplus.c ch12_sum.c
macbook:C_ch12> vi ch12_sum.c 
macbook:C_ch12> gcc ch12_sum.c
ch12_sum.c:11:27: error: expected ';' in 'for' statement specifier
   11 |         for (int i=0; i<N i++) {
      |                           ^
1 error generated.
macbook:C_ch12> ./a.out
  a[0] is 0
  a[1] is 1
  a[2] is 2
  a[3] is 3
  a[4] is 4
  a[5] is 5
  a[6] is 6
  a[7] is 7
Now change the values 
  a[0] is 0
  a[1] is 3
  a[2] is 6
  a[3] is 9
  a[4] is 12
  a[5] is 15
  a[6] is 18
  a[7] is 21
macbook:C_ch12> ./a.out
  a[0] is 0
  a[1] is 1
  a[2] is 2
  a[3] is 3
  a^[[2;2R^[[3;3R[4] is 4
  a[5] is 5
  a[6] is 6
  a[7] is 7
Now change the values 
  a[0] is 0
  a[1] is 3
  a[2] is 6
  a[3] is 9
  a[4] is 12
  a[5] is 15
  a[6] is 18
  a[7] is 21
macbook:C_ch12> ./a.out
  a[0] is 0
  a[1] is 1
  a[2] is 2
  a[3] is 3
  a[4] is 4
  a[5] is 5
  a[6] is 6
  a[7] is 7
Now change the values 
  a[0] is 0
  a[1] is 3
  a[2] is 6
  a[3] is 9
  a[4] is 12
  a[5] is 15
  a[6] is 18
  a[7] is 21
macbook:C_ch12> 
macbook:C_ch12> 
macbook:C_ch12> 
macbook:C_ch12> 
macbook:C_ch12> 
macbook:C_ch12> 
macbook:C_ch12> 
macbook:C_ch12> 
macbook:C_ch12> 
macbook:C_ch12> 
macbook:C_ch12> 
macbook:C_ch12> ./a.out
  a[0] is 0
  a[1] is 1
  a[2] is 2
  a[3] is 3
  a[4] is 4
  a[5] is 5
  a[6] is 6
  a[7] is 7
Now change the values 
  a[0] is 0
  a[1] is 3
  a[2] is 6
  a[3] is 9
  a[4] is 12
  a[5] is 15
  a[6] is 18
  a[7] is 21
macbook:C_ch12> gcc ch12_sum.c
ch12_sum.c:11:27: error: expected ';' in 'for' statement specifier
   11 |         for (int i=0; i<N i++) {
      |                           ^
1 error generated.
macbook:C_ch12> vi ch12_sum.c 
macbook:C_ch12> gcc ch12_sum.c
macbook:C_ch12> ./a.out       
  a[0] is 0
  a[1] is 1
  a[2] is 2
  a[3] is 3
  a[4] is 4
  a[5] is 5
  a[6] is 6
  a[7] is 7
  a[8] is 8
  a[9] is 9
Now sum the values 
  sum is 45
macbook:C_ch12> cat ch12_sum.c 
#include <stdio.h>
#define N 10

int main(){
        int a[10], *p, *q;
        p = &a[0];

        // initialize the array a
        for (int i=0; i<N; i++)
          a[i] = i;
        for (int i=0; i<N; i++) {
          printf("  a[%d] is %d\n", i, a[i]);
        }

        printf("Now sum the values \n");

int sum = 0;
for (p = &a[0]; p < &a[N]; p++)
  sum += *p;

        printf("  sum is %d\n", sum);

        return 0;
}
macbook:C_ch12> exit

Saving session...
...copying shared history...
...saving history...truncating history files...
...completed.

Script done on Mon Oct 13 18:44:41 2025