The document is a series of slides from a lecture on C programming pointers by Professor Joongheon Kim. It contains examples of using pointers with basic data types like integers and characters, as well as more complex examples involving pointers to arrays and functions. The examples are presented step-by-step with diagrams and explanations to illustrate how pointers store memory addresses and can be used to indirectly access and modify values in memory.

1. Professor Joongheon Kim
https://joongheon.github.io
C Programming
C Programming
Pointer (Examples)
Directed by Prof. Joongheon Kim
Korea University, School of Electrical Engineering
Artificial Intelligence and Mobility Laboratory
https://joongheon.github.io
joongheon@korea.ac.kr

2. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Outline
• Pointers
• Pointers and Arrays
• Pointers and Functions
2

3. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.1)
3
• Introduction Example
Int: x
0xf1

4. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.1)
4
• Introduction Example
Int: x
0xf1
Pointer (Int): ptr_x

5. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.1)
5
• Introduction Example
100
Int: x
0xf1
Pointer (Int): ptr_x

6. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.1)
6
• Introduction Example
100
0xf1
0xf1
Int: x
Pointer (Int): ptr_x

7. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.1)
7
• Introduction Example
100
0xf1
0xf1
x: 100, &x: 0xf1
Int: x
Pointer (Int): ptr_x

8. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.1)
8
• Introduction Example
100
0xf1
0xf1
x: 100, &x: 0xf1
*ptr_x: 100, ptr_x: 0xf1
Int: x
Pointer (Int): ptr_x

9. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.1)
9
• Introduction Example
200
0xf1
0xf1
x: 100, &x: 0xf1
*ptr_x: 100, ptr_x: 0xf1
Int: x
Pointer (Int): ptr_x

10. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.1)
10
• Introduction Example
200
0xf1
0xf1
x: 100, &x: 0xf1
*ptr_x: 100, ptr_x: 0xf1
x: 200, *ptr_x: 200
Int: x
Pointer (Int): ptr_x

11. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.2)
11
• Address of Arrays 1
Int: x
0xf1
2
Int: y
0xcc
Int Array: z[2]
0xd3

12. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.2)
12
• Address of Arrays 1
0xf1
2
0xcc
0xd3
Int: x
Int: y
Int Array: z[2]
Pointer
(Int): ptr

13. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.2)
13
• Address of Arrays 0xf1
2
0xcc
0xd3
Int: x
Int: y
Int Array: z[2]
Pointer
(Int): ptr
0xf1 1

14. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.2)
14
• Address of Arrays
ptr: 0xf1
1
0xf1
2
0xcc
0xd3
Int: x
Int: y
Int Array: z[2]
Pointer
(Int): ptr
0xf1

15. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.2)
15
• Address of Arrays
ptr: 0xf1
1
0xf1
1
0xcc
0xd3
Int: x
Int: y
Int Array: z[2]
Pointer
(Int): ptr
0xf1

16. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.2)
16
• Address of Arrays
ptr: 0xf1
y: 1
1
0xf1
1
0xcc
0xd3
Int: x
Int: y
Int Array: z[2]
Pointer
(Int): ptr
0xf1

17. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.2)
17
• Address of Arrays
ptr: 0xf1
y: 1
0
0xf1
1
0xcc
0xd3
Int: x
Int: y
Int Array: z[2]
Pointer
(Int): ptr
0xf1

18. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.2)
18
• Address of Arrays
ptr: 0xf1
y: 1
*ptr: 0
0
0xf1
1
0xcc
0xd3
Int: x
Int: y
Int Array: z[2]
Pointer
(Int): ptr
0xf1

19. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.2)
19
• Address of Arrays
ptr: 0xf1
y: 1
*ptr: 0
0
0xf1
1
0xcc
0xd3
Int: x
Int: y
Int Array: z[2]
Pointer
(Int): ptr
0xd3

20. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.2)
20
• Address of Arrays
ptr: 0xf1
y: 1
*ptr: 0
ptr: 0xd3
0
0xf1
1
0xcc
0xd3
Int: x
Int: y
Int Array: z[2]
Pointer
(Int): ptr
0xd3

21. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.2)
21
• Address of Arrays
ptr: 0xf1
y: 1
*ptr: 0
ptr: 0xd3
z[0]: 1212133
/* garbage */
0
0xf1
1
0xcc
0xd3
Int: x
Int: y
Int Array: z[2]
Pointer
(Int): ptr
0xd3

22. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.3)
22
• Arithmetic 1 100
0xf1
200
0xcc
0xd3
Int: x
Int: y
Int: sum

23. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.3)
23
• Arithmetic 1 100
0xf1
200
0xcc
0xd3
Int: x
Int: y
Int: sum
Pointer (Int): ptr_x
Pointer (Int): ptr_y
Pointer (Int): ptr_sum

24. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.3)
24
• Arithmetic 1 100
0xf1
200
0xcc
0xd3
Int: x
Int: y
Int: sum
Pointer (Int): ptr_x
0xf1
Pointer (Int): ptr_y
0xcc
Pointer (Int): ptr_sum
0xd3

25. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.3)
25
• Arithmetic 1 100
0xf1
200
0xcc
300
0xd3
Int: x
Int: y
Int: sum
Pointer (Int): ptr_x
0xf1
Pointer (Int): ptr_y
0xcc
Pointer (Int): ptr_sum
0xd3

26. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.3)
26
• Arithmetic 1
ptr_x: 0xf1, ptr_y: 0xcc
*ptr_x: 100, *ptr_y: 200
*ptr_sum: 300
100
0xf1
200
0xcc
300
0xd3
Int: x
Int: y
Int: sum
Pointer (Int): ptr_x
0xf1
Pointer (Int): ptr_y
0xcc
Pointer (Int): ptr_sum
0xd3

27. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.4)
27
• Arithmetic 2 100
0xf1
Int: x
Pointer (Int): ptr_x

28. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.4)
28
• Arithmetic 2 100
0xf1
Int: x
Pointer (Int): ptr_x
0xf1

29. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.4)
29
• Arithmetic 2 300
0xf1
Int: x
Pointer (Int): ptr_x
0xf1

30. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.4)
30
• Arithmetic 2 300
0xf1
Int: x
Pointer (Int): ptr_x
0xf1
x: 300
*ptr_x: 300, ptr_x: 0xf1

31. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 1.5)
• Operator *
31
0x7ffd316b35a7
A A

32. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Outline
• Pointers
• Pointers and Memory
• Multiple Pointers
• Pointers and Arrays
• Pointers and Functions
32

33. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 2.1)
• Pointer and Memory (char)
33
1
A
65 (= ‘A’)
097
098
099
100
101
102
103
104
105
106
107
108
109
110
111
c (char)
• ASCII code of “A”
It says sizeof(c) is 1.
It means “char” uses 1 Byte in memory.
• Address
(or Starting Address)

34. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 2.2)
• Pointer and Memory (int)
34
4
10
097
098
099
100
101
102
103
104
105
106
107
108
109
110
111
a (int)
It says sizeof(a) is 4.
It means “int” uses 4 Bytes in memory.
10

35. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 2.3)
• Pointer and Memory (double)
35
8
10
097
098
099
100
101
102
103
104
105
106
107
108
109
110
111
a (double)
It says sizeof(a) is 8.
It means “double” uses 8 Bytes in memory.
10

36. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 2.4)
• Pointer and Memory Address (char)
36
65 (= ‘A’)
66 (= ‘B’)
0x7fffc67cfb66
0x7fffc67cfb67
0x7fffc67cfb68
a (char)
0x7fffc67cfb66
0x7fffc67cfb67
0x7fffc67cfb67
0x7fffc67cfb68
b (char)
&a
&b
&a+1
&b+1

37. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 2.5)
• Pointer and Memory Address (int)
37
0x7ffdcbaf29d0
0x7ffdcbaf29d1
0x7ffdcbaf29d2
0x7ffdcbaf29d3
0x7ffdcbaf29d4
0x7ffdcbaf29d5
0x7ffdcbaf29d6
0x7ffdcbaf29d7
0x7ffdcbaf29d8
0x7ffdcbaf29d0
0x7ffdcbaf29d4
0x7ffdcbaf29d4
0x7ffdcbaf29d8
&a
&b
&a+1
&b+1
a (int)
1
b (int)
2

38. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 2.6)
• Type Conversion in Address
38
0x7fff7a2ab1b7 0x7fff7a2ab1b7 0x7fff7a2ab1b7
0x7fff7a2ab1b8 0x7fff7a2ab1b8 0x7fff7a2ab1bb

39. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 2.7)
• Sizes of Individual Types (char and int) 1
39
A A
1 8
1 8
=====
10 10
4 8
4 8

40. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 2.8)
• Sizes of Individual Types (char and int) 2
40
1 1 8
4 4 8

41. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Outline
• Pointers
• Pointers and Memory
• Multiple Pointers
• Pointers and Arrays
• Pointers and Functions
41

42. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 3.1)
• Double Pointer
42
A A A
0x7fff14e17fc3 0x7fff14e17fc3 0x7fff14e17fc3
=====
10 10 10
0x7fff14e17fc4 0x7fff14e17fc4 0x7fff14e17fc4

43. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 3.2)
• Multiple Pointer
43
10 10 10 10
4 8 8 8
4 8 8 8

44. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers (Example 3.3)
• Size of Multiple Pointers
44
10 10 10
4 4 4
4 8 8

45. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Outline
• Pointers
• Pointers and Memory
• Multiple Pointers
• Pointers and Arrays
• Pointers and Functions
45

46. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Arrays (Introduction)
• Array x
• x: constant pointer
pointing the first element x[0]
• Thus, the value of x is 1000, i.e., x = &x[0] = 1000
• If we declare p as an integer pointer (int *p;),
the pointer p can point to the array x by p=x; (equivalent to p = &x[0])
• p = &x[0] // == 1000
p+1 = &x[1] // == 1004
p+2 = &x[2] // == 1008
p+3 = &x[3] // == 1012
p+4 = &x[4]
• *(p+3) gives the value of x[3], i.e., 4.
46
int x[5] = {1, 2, 3, 4, 5};
1 2 3 4 5
x[0] x[1] x[2] x[3] x[4]
1000 1004 1008 1012 1016

47. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Arrays (Example 4.1)
47

48. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Arrays (Character Strings)
• Character String x
48
char x[5] = “good”;
g o o d 0
x[0] x[1] x[2] x[3] x[4]
1000 1004 1008 1012 1016
char *x = “good”; x

49. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Arrays (Example 4.2)
R e p u b l i c o f K o r e a 0
49
P . R . C h i n a 0
J a p a n 0
name[0]
name[1]
name[2]

50. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Outline
• Pointers
• Pointers and Memory
• Multiple Pointers
• Pointers and Arrays
• Pointers and Functions
50

51. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Functions (Example 5.1)
51
20
Int: x
0xf1
10
Int: y
0xcc
Int: s
0xfd
Int: d
0xdc

52. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Functions (Example 5.1)
52
20
Int: x
0xf1
10
Int: y
0xcc
Int: s
0xfd
Int: d
0xdc

53. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Functions (Example 5.1)
53
20
Int: x
0xf1
10
Int: y
0xcc
Int: s
0xfd
Int: d
0xdc
20
Int: a
10
Int: b
0xfd
Pointer
(Int): sum
0xdc
Pointer
(Int): dif

54. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Functions (Example 5.1)
54
20
Int: x
0xf1
10
Int: y
0xcc
30
Int: s
0xfd
10
Int: d
0xdc
20
Int: a
10
Int: b
0xfd
Pointer
(Int): sum
0xdc
Pointer
(Int): dif

55. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Functions (Example 5.1)
55
20
Int: x
0xf1
10
Int: y
0xcc
30
Int: s
0xfd
10
Int: d
0xdc
s: 30, d: 10
20
Int: a
10
Int: b
0xfd
Pointer
(Int): sum
0xdc
Pointer
(Int): dif

56. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Functions (Example 5.2)
56
10
Int: x
0xf1
20
Int: y
0xcc
x: 10, y: 20

57. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Functions (Example 5.2)
57
10
Int: x
0xf1
20
Int: y
0xcc
&x
x: 10, y: 20
&y

58. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Functions (Example 5.2)
58
10
Int: x
0xf1
20
Int: y
0xcc
&x
&y
Int: t
0xfc
x: 10, y: 20
0xf1
Pointer
(Int): a
0xcc
Pointer
(Int): b

59. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Functions (Example 5.2)
59
x: 10, y: 20
10
Int: x
0xf1
20
Int: y
0xcc
&x
&y
10
Int: t
0xfc
0xf1
Pointer
(Int): a
0xcc
Pointer
(Int): b

60. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Functions (Example 5.2)
60
x: 10, y: 20
20
Int: x
0xf1
20
Int: y
0xcc
&x
&y
10
Int: t
0xfc
0xf1
Pointer
(Int): a
0xcc
Pointer
(Int): b

61. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Functions (Example 5.2)
61
x: 10, y: 20
20
Int: x
0xf1
10
Int: y
0xcc
&x
&y
10
Int: t
0xfc
0xf1
Pointer
(Int): a
0xcc
Pointer
(Int): b

62. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Pointers and Functions (Example 5.2)
62
x: 10, y: 20
x: 20, y: 10
20
Int: x
0xf1
10
Int: y
0xcc
&x
&y
10
Int: t
0xfc
0xf1
Pointer
(Int): a
0xcc
Pointer
(Int): b

63. Professor Joongheon Kim
https://joongheon.github.io
C Programming
Q&A
Thank you for your attention!
• More questions?
• joongheon@korea.ac.kr
• More details?
• https://joongheon.github.io/
63