Chap' 5 Pointers and Arrays

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Chap. 5 Pointers and Arrays

• 5.1 Pointers and Adresses
• 5.2 Pointers and Function Arguments
• 5.3 Pointers and Arrays
• 5.4 Address Arithmetic
• 5.5 Character Pointers and Functions
• 5.6 Pointer Arrays Pointers to Pointers
• 5.7 Multidimensional Arrays
• 5.8 Initialization of Pointer Arrays
• 5.9 Pointers vs Multi-dimensional Arrays
• 5.10 Command-line Argument
• 5.11 Pointers to Functions
• 5.12 Complicated Declarations

Session 7 - 4 May 2004
Session 9 - 18 May 2004
!!! 11 May 2004 Mid Term Test !!!
Imperative Programming, B. Hirsbrunner,
diuf.unifr.ch/pai/ip04
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5.1 Pointers and Addresses

• Pointer
• A pointer is a variable that contains the
  address of a variable
• Address Operator
• x is the address of the variable x
• Indirection or Dereferencing Operator
• p access the object the pointer p points to

A first example main() int x 1 int
p p x printf(d, p)
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A Mystery Program
Reminder
include ltstdio.hgt main() int i 1 int
p int q p i q p
printf("\nmystery d p p p", p0,
p0, p1, p2) p 3 printf("
p\r\n", p)
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Output of the Mystery Program
i 1 p BFFFFB08 q bffffb0c p 1
i BFFFFB08 p bffffb0c q 1 q
BFFFFB08 q bffffb10 i
1 i 0xbffffb08 p 1
p 0xbffffb08 mystery 1 0xbffffb08
0xbffffb0c 0xbffffb10 0xbffffb14
Memory Diagram
Full Memory Diagram
Reminder int i1 int pi int qp
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5.2 Pointers and Function Arguments

• C passes arguments to functions by value !

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5.3 Pointers and Arrays
As p is a variable, pa or p are legalbut as
an array name is not a variable, expression like
ap or a are illegal !
Tricky p-a is legal, but not pa !
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Array as a Parameter of a Function
// return length of string s int strlen(char
s) int n for (n 0 s ! '\0'
s) n return n

• The following calls will work

strlen(a) // char a10
strlen(p) // char p
strlen("hello world") // string constant !!
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A Test Program

• include ltstdio.hgt
• / Return length of string s /
• int strlen(char s)
• int n
• for (n 0 s ! '\0' s)
• n
• return n
• main()
• char a "hello"
• char p a
• (1) printf("d\n", strlen(a))
• (2) printf("d\n", strlen(p))

Hint Draw the execution diagram for (1), (2) and
(3)