STRUCTURES

1
STRUCTURES

• CHAPTER 9

2
Structures provides a means to aggregate
variables of different types

• EXAMPLE You have a file including the records
  below
• ID NAME GRADE
• 12 Joe A
• 17 Mary B
• 89 Sue A
• 10 Tom C
• int id4 char names4 char grade4
• id012 names1Joe grade0A

3
Structures
record is the tag name
struct record int ID char name char
grade struct record s1 struct record
s2 s1.ID12 s1.nameJoe s1.gradeA s2.ID1
7 s2.nameMary s2.gradeB

• ID NAME GRADE
• 12 Joe A
• 17 Mary B
• 89 Sue A
• 10 Tom C

struct record is the new type
4
Structures
struct record int ID char name char grade
struct record s1 struct record s2
s1
ID
name
grade
s2
ID
name
grade
5
Structures

• struct record
• int ID char name
• char grade
• struct record s4
• s0.ID12
• s0.nameJoe
• s0.gradeA
• s1.ID17 s1.nameMary
• s1.gradeB
• s3s1

ID
name
grade
s0 ?
ID
name
grade
s1 ?
ID
name
grade
s2 ?
s3 ?
ID
name
grade
ID NAME GRADE 12 Joe A 17 Mary B 89
Sue A 10 Tom C
6
Structures DECLARATION ALTERNATIVES

• Declaration 1
• struct record int ID char name char
  grade
• struct record s1
• struct record s2
• struct record s3
• Declaration 2
• struct record int ID char name char
  grade s1, s2
• struct record s3

7
Structures DECLARATION ALTERNATIVES

• Declaration 1
• struct record
• int ID char name char grade
• struct record s1
• struct record s2
• Declaration 3
• struct
• int ID char name char grade s1, s2
• / no tag name /
• / no permission to declare other variables of
  this type /

8
Structures DECLARATION ALTERNATIVES

• Declaration 4
• struct record int ID char name char
  grade
• typedef struct record rec
• rec s1
• struct record s2
• Declaration 5 / high degree of modularity and
  portability /
• typedef struct int ID char name char
  grade rec
• rec s1
• rec s2

9
INITIALIZATION

• struct names
• char name10
• int length
• int weigth man3 Tom,180,65,
• George, 170,68,
• Bob, 190,100
• struct names woman2Mary, 170, 55, Sue,
  160,67
• struct names your
• your. nameJane
• your.length160
• your.weigth50

10
INITIALIZATION

• includeltstdio.hgt
• struct physical_info
• int length
• int weigth
• struct record
• int salary
• int working_hour
• struct physical_info man
• main()
• struct record s1
• s1.salary10000
• s1.working_hour 6
• s1.man.length180
• s1.man.weigth78
• / struct record b2 10000, 7, 190, 78
  

11
STRUCTURES AS FUNCTION ARGUMENTS 1

• struct date int day int month int year
• struct date calculate ( struct date d)
• main()
• struct date today 12, 10, 2005
• struct date next_day
• next_day calculate(today)
• printf(Next day is d.d.d,
  next_day.day,next_day.month,next_day.year)
• struct date calculate ( struct date d)
• struct day n
• if( d.day30)
• if(d.month12) n.day1 n.month1
  n.yeard.year1
• else n.day1n.monthd.month1
  n.yeard.year
• else n.dayd.day1 n.monthd.month
  n.yeard.year
• return n

12
STRUCTURES AS FUNCTION ARGUMENTS 2

• includeltstdio.hgt
• struct student char last_name int st_id int
  grade
• int average ( struct student x, int size)
• main()
• typedef struct student st
• st class30 int av,i
• for(i0ilt30i)
• scanf(d, classi.grade)
• avaverage(class,30) // average(class0,30)
• int average ( struct student x, int size) //
  int average ( struct student x, int size)
• // int average ( st x, int size)
• int a0 int i
• for(i0iltsizei)

13
STRUCTURES AS FUNCTION ARGUMENTS 3

• includeltstdio.hgt
• struct complex double re double im
• void add_on( struct complex a , struct complex
  b) /it will add these two complex
• numbers and assign the result to a /
• main()
• struct complex x,y
• x.re2 y.re4
• x.im3 y.im6
• printf(x is d di\n, x.re, x.im)
• printf(y is d di\n, y.re, y.im)
• add_on(x,y)
• printf(x is d di\n, x.re, x.im)
• printf(y is d di\n, y.re, y.im)
• void add_on( struct complex a , struct complex
  b)
• (a).re (a).re (b).re // a-gtre a-gtre
  b-gtre
• (a).im (a).im (b).im //a-gtim a-gtim
  b-gtim

14
ACCESSING MEMBERS OF A STRUCTURE

• struct student
• char last_name int st_id char grade
• main()
• struct student tmp, ptmp
• tmp.gradeA tmp.last_nameCasper
  tmp.st_id1000
• printf(d\n,tmp.grade)
• printf(d\n,p-gtgrade)
• printf(s\n,tmp.last_name)
• printf(s\n,p-gtlast_name)
• printf(s\n,(p).last_name)
• printf(c\n,(p-gtlast_name)2)
• printf(c\n,((p-gtlast_name2))
• printf(c\n,p-gtlast_name1) // -gt
  operator has a higher level of precedence
• printf(c\n,((p-gtlast_name))1)

15
STACKS

• define STACK_SIZE 4
• typedef struct st
• int data STACK_SIZE int top stack
• void reset(stack stk)
• stk-gttop-1
• void push( int c, stack stk)
• if( stk-gttop! STACK_SIZE-1)
• stk-gttop stk-gtdatastk-gttopc
• else printf(Stack is full!!\n)
• int pop (stack stk)
• if(stk-gttop!-1)

main() int k 1,2,3,4,5 stack n int
x reset(n) push(4,n) push(5,n) pus
h(3,n) push(2,n) push(1,n) x
pop(n) push(11,n) x pop(n) x
pop(n) x pop(n) push(3,n) push(2,n) x
pop(n)
16
UNIONS

• includeltstdio.hgt
• union int_or_char
• char c
• int i
• main()
• union int_or_char test
• test.i 83
• printf("i d\n", test)
• printf("c c\n",test)
• test.c 'A'
• printf("i d\n",test)
• printf("c c\n", test)