Chap 3 ????

1
Chap 3 ????

• 3.1 ?????????????????
• 3.2 ?????????????
• 3.3 ????????

2
3.1 ?????????????????

• ?3-1 ??10???,??????????????????????
• 3.1.1 ????
• 3.1.2 ????
• 3.1.3 ??????????
• 3.1.4 ????
• 3.1.5 else-if ??

3
3.1.1 ????

• include ltstdio.hgt
• int main(void)
• int digit, i, letter, other
• char ch  
• digit letter other 0
• printf(Enter 10 characters ")
• for(i 1 i lt 10 i)
• ch getchar() / ?????????,????? ch
  /
• if((ch gt 'a' ch lt 'z' ) ( ch gt
  'A' ch lt 'Z'))
• letter
• else if(ch gt '0' ch lt '9') /
  ??ch????? /
• digit
• else
• other
• printf("letterd,digitd,otherd\n",letter,d
  igit,other)
• return 0

input 10 characters Reold 123? letter5,
digit3, other2
????????? ???????
4
3.1.2 ????

• char ch
• (ch gt 'a' ch lt 'z' ) ( ch gt 'A' ch lt
  'Z')
• (ch gt '0' ch lt '9')
• ?????
• ????ch
• ???? 'a'

5
????

• 'a' 'z' 'A' 'Z' '0' '9' ' ' '\n'
• ASCII????????????
• ??????????( ASCII ?)
• '0'-'9'
• 'A'-'Z'
• 'a'-'z'

???? 1 ????? '1'
6
????

• char ch
• ??????ch,??????????
• ch 'A'

7
3.1.3 ???????????

• ??????getchar
• ??????
• char ch
• ch getchar( )
• ??????putchar
• ??????
• putchar(????)

char ch ch getchar() putchar (ch) putchar
(?')
?????????
8
??scanf?printf??????

• double value1, value2
• char operator
• printf(Type in an expression )
• scanf(lfclf, value1, operator, value2)
• printf(.2f c .2f, value1, operator, value2)

Type in an expression 10.05.61 10.00 5.61
9
3.1.4 ????

• (ch gt 'a' ch lt 'z' ) ( ch gt 'A' ch lt
  'Z')
• ch gt '0' ch lt '9
• ????????(true/false)
• ?????

10
3??????

• ???
• ???
• ??? !

X Y
X Y
X
Y
X
Y
! X
X
11
????????

• ??? ??? ??? !
• (xgt1)(ygt1) (xgt1)(ygt1) (xgt1)
• !(xgt1) ? xlt1

12
????????

• ??? ??? ??? !
• a b ab ab !a
• ? ? ? ? ?
• ? ? ? ? ?
• ? ? ? ? ?
• ? ? ? ? ?

13
?????

• ??????????????????????????
• (ch gt 'a') (ch lt 'z')
• ??ch ?????????
• ?
• ch gt 'a' ch lt 'z'
• (ch gt 'a' ch lt 'z') ( ch gt 'A' ch lt
  'Z')
• ??ch ???????

14
?????

• ?3-2 ?????????C????
• ch ???????
• ch ' ' ch '\n'
• number???
• number 2 0
• year ???,? year ?? 4 ?????? 100 ??,? year ?? 400
  ??
• (year 4 0 year 100 ! 0) (year
  400 0)

15
3.1.5 else if ??

• if((ch gt 'a' ch lt 'z' )( ch gt 'A' ch
  lt 'Z'))
• letter
• else if(ch gt '0' ch lt '9')
• digit
• else
• other
• ??????

16
else if ??
if((ch gt 'a' ch lt 'z' )( ch gt 'A' ch
lt 'Z')) letter else if(ch gt '0' ch
lt '9') digit else other

• if (???1) ??1
• else if (???2) ??2
• else if (???n-1) ??n-1
• else ??n

17
??????

• ?3-3 ??????

18
???-??????

• include ltstdio.hgt
• int main(void)
• double x, y
• printf("Enter x")
• scanf("lf", x)
• if (x lt 0)
• y 0
• else if (x lt 15)
• y 4 x / 3
• else
• y 2.5 x - 10.5
• printf("f(.2f) .2f\n", x, y)
• return 0

19
3.2 ?????????????

• ?3-4 ?????????????
• 3.2.1 ????
• 3.2.2 switch??

20
3.2.1 ????

• ?????????4???,??(crisps)????(popcorn)????(chocolat
  e)???(cola),???????3.0?2.5?4.0?3.5????????????,???
  ??????????,???????5??,????????5??,???????????????
  ?14,???????????0,??????????,?????0?
• 1 Select crisps
• 2 Select popcorn
• 3 Select chocolate
• 4 Select cola
• 0 Exit

21
1 Select crisps 2 Select popcorn 3 Select
chocolate 4 Select cola 0 Exit Enter choice
1 price 3.0 1 Select crisps 2 Select
popcorn 3 Select chocolate 4 Select cola
0 Exit Enter choice 7 price 0.01 Select
crisps 2 Select popcorn 3 Select
chocolate 4 Select cola 0 Exit Enter choice
0 Thanks

• include ltstdio.hgt
• Int main(void)
• int choice, i double price
• for( i 1 i lt 5 i)
• printf("1 Select crisps \n")
• printf("2 Select popcorn \n")
• printf("3 Select chocolate \n")
• printf("4 Select cola \n")
• printf("0 exit \n")
•   printf("Enter choice ")
• scanf("d", choice)
•   if(choice 0) break
• switch (choice)
• case 1 price3.0 break
• case 2 price2.5 break
• case 3 price4.0 break
• case 4 price3.5 break
• default price0.0 break

22
3.2.2 switch??

• ?????????,3???
• 1??switch????????????break??
• switch(???)
• case ?????1???1 break
• case ?????2???2 break
• ....
• case ?????n???n break
• default ???n1 break

23
switch (choice) case 1 price3.0 break
case 2 price2.5 break case 3
price4.0 break case 4 price3.5 break
default price0.0 break

• switch(???)
• case ?????1???1 break
• case ?????2???2 break
• ....
• case ?????n???n break
• default ???n1 break

?else-if ?????
24
???????

• ?3-5 ?????????? ??? ???????????,???????
• ??
• ??3.14.8
• ??7.9

25
???

• include ltstdio.hgt
• int main(void)
• char operator double value1, value2
• printf("Type in an expression ")
• scanf("lfclf", value1, operator,
  value2)
• switch(operator)
• case ''
• printf(".2f\n", value1value2)
• break
• case '-'
• printf(".2f\n", value1-value2)
• break
• case ''
• printf(".2f\n", value1value2)
• break
• case '/'
• printf(".2f\n", value1/value2)
• break
• default

Type in an expression 3.14.8 7.9
26
2??switch????break

• switch(???)
• case ?????1???1
• case ?????2???2
• ....
• case ?????n???n
• default ???n1

27

• switch(???)
• case ?????1???1
• case ?????2???2
• ....
• case ?????n???n
• default ???n1

switch (choice) case 1 price3.0 case
2 price2.5 case 3 price4.0 case 4
price3.5 default price0.0
price?
28
3??switch?????????break

• ?3-6 ??10???,????????????????????????

?3-1 ??10???,??????????????????????
29

• int main(void)
• int blank, digit, i, other char ch
  
• blank digit other 0
• printf("Enter 10 characters ")
• for(i 1 i lt 10 i)
• ch getchar()
• switch (ch)
• case ' '
• case '\n'
• blank
• break
• case '0' case '1' case '2' case
  '3' case '4'
• case '5' case '6' case '7' case
  '8' case '9'
• digit
• break
• default
• other
• break

Enter 10 characters Reold 123? blank1, digit3,
other6
30
3.3 ????????

• ???????????????????
• ?????(if ? switch)????
• 3.3.1 ????????? if ??
• 3.3.2 ????????? if ???switch??

31
3.3.1 ????????? if ??

• if (???)
• ??1
• else
• ??2

if (???) ??1
????
32
????????

• ?3-7 ??1???,????????????

number 2 0
33
???-????????

• include ltstdio.hgt
• int main(void)
• int number
• printf("Enter a number ")
• scanf("d", number)
• if(number 2 0)
• printf("Tne number is even. \n")
• else
• printf("Tne number is odd. \n")
• return 0

34
????

• ?3-8 ??1???,??????? ?

?number lt 0?,number - number ?number gt
0?,number ?
35
???-????

• include ltstdio.hgt
• int main(void)
• int number
• printf("Enter a number ")
• scanf("d", number)
• if(number lt 0)
• number -number
• printf("The absolute value is d.\n",
  number)
• return 0

Enter a number 10 The absolute value is 10.
Enter a number -300 The absolute value is 300.
36
3.3.2 ????????? if ???switch??

• ??????????
• ????
• ??? if ??
• else if ??
• ??? if - else??
• switch??

37
??? if ??

• if (???)
• ??1
• else
• ??2

if ??
if ??

• else if ??
• ??? if - else??

38
else if ??

• if (???1) ??1
• else if(???2) ??2
• else if(???n-1) ??n-1
• else ??n

n?????n-1???
39
??? if else ??

• if(???1)
• if(???2) ??1
• else ??2
• else
• if(???3) ??3
• else ??4

40
2???if?????

• if (x lt 1) y x 1
• else if (x lt 2) y x 2
• else y x 3

if (x lt 2) if (x lt 1) y x 1 else
y x 2 else y x 3
41
else ? if ???

• if(???1)
• if(???2) ??1
• else
• if(???3) ??3
• else ??4

• if(???1)
• if(???2) ??1
• else ??2
• else
• if(???3) ??3
• else ??4

else ???????????? else ???? if ??

• if(???1)
• if(???2) ??1
• else
• if(???3) ??3
• else ??4

42
??else ? if ???

• ?3-10 ???? if ??,? else ??1? if ???
• if (x lt 2)
• if (x lt 1) y x 1
• else y x 2

??????????
if (x lt 2) if (x lt 1) y x 1 else y
x 2
if (x lt 2) if (x lt 1) y x 1
else else y x 2
43
????

• ????????????????
• switch ???? break ??????
• ?????????????????????????????
• ????????????????