slide function 2016

7/25/2019 Slide Function 2016

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FunctionFunction


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FunctionFunction Several function you know:Several function you know:

main ( ) user defined functionmain ( ) user defined function

printf( ) & scanf( ) library functionprintf( ) & scanf( ) library function

Function enables program to be break up intoFunction enables program to be break up intosegmentssegments


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FunctionFunction Advantages:Advantages:

Dividing the program into separate well-denedDividing the program into separate well-dened

functions enable each function to be written andfunctions enable each function to be written and

tested separately. t can simplies the process oftested separately. t can simplies the process of

getting the total program to work.getting the total program to work.

when a big program is broken into functions! pro"ectwhen a big program is broken into functions! pro"ect

can be divided to di#erent programmers. $achcan be divided to di#erent programmers. $ach

programmer responsible on di#erent functions.programmer responsible on di#erent functions.

%here are a set of functions in & libraries which are%here are a set of functions in & libraries which are

free to use. t will speeds up the programfree to use. t will speeds up the program

development.development.


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Dene Function

'eneral form of a function:'eneral form of a function:

DataType function_name(parameter_list)DataType function_name(parameter_list)

{{

body of codebody of code

}}

Return values data type

Parameter passing

* Function Definition


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void hello (void)

{ printf(hello world !\n )}

$(ample )$(ample )

To create simple function:

Data type Name Parameter passing


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$(ample )$(ample )include"stdio#h$include"stdio#h$void hello(void)void hello(void){{ printf(hello world !\n )printf(hello world !\n )

}}

void main()void main(){{

hello()hello()}}note the use of the key word void.note the use of the key word void.

The CFunctionbody outsideOf the main

program

The c function called fromthe main program (calling fu

Called function


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*ain memory + Func memory*ain memory + Func memoryinclude"stdio#h$

void func (){

int twotwo%&

printf('two is d\n' two)}

int main (void){

int oneone % *func ()

printf('+ne is d\n' one)

return (,)}

Two is 2

One is 1


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*ain memory + Func memory*ain memory + Func memoryvoid func()

{ int local-ylocal % &y % .- % local / y

printf ('\t - % d\n' -)printf ('\t local in func % d\n' local)

}

int main (void){

int locallocal % *

printf('local in main % d\n' local)func()

printf ('local in main % d\n' local)

return (,)}

local in main 1

! "

local in func 2

local in main 1


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,uestion ),uestion )

rite a program to calculate the arearite a program to calculate the area

of a circle using function. %heof a circle using function. %he

program should allow user to enterprogram should allow user to enter

the value of radius and display thethe value of radius and display the

result with proper unit.result with proper unit.


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assing parameters /assing parameters /

arguments to the functionarguments to the function

hen function is called! the calling function mayhen function is called! the calling function may

have to pass some values to the called function.have to pass some values to the called function.

%here are 0 ways to pass the parameter/arguments%here are 0 ways to pass the parameter/arguments

to the called function.to the called function.

1i2 call by1i2 call by valuevalue3 values of the variables are passed3 values of the variables are passed

by the calling function to the called function.by the calling function to the called function.

1ii2 call by1ii2 call by referencereference3 address of the variables are3 address of the variables are

passed by the calling function to the called function.passed by the calling function to the called function.


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%he argument names in the function declaration%he argument names in the function declaration

and function denition need not to be the sameand function denition need not to be the same

but the data types or the arguments must match.but the data types or the arguments must match.

%he arguments in the dened function must place%he arguments in the dened function must place

in the correct order too.in the correct order too.




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Function may accept as many parameters#argumentsas it

need$ Function wit% no parameter passing is fine too$

void prn_messa0e(int 1)

{int i

printf( 2ere is the messa0e3\n')

for (i % , i "1 i//){ printf( 2ave a nice day!\n')}

}

One parameter passing




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include"stdio#h$

void prn_messa0e(int 1){int i

printf ('2ere is the messa0e3\n')for (i % , i "1 i//){ printf (' 2ave a nice day!\n')}

}

int main (void){

int n

printf ('There is a messa0e for you# \n')printf ('2ow many times do you want to see it4')scanf ('d' 5n)

prn_messa0e(n)return (,)

}

calling function

$(ample 0


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Function may accept as many parametersas it need$

void prn_messa0e(int 1 int 6 int m){

int iprintf( 2ere is the messa0e3\n')

for (i % , i "1 i//)

{ printf( 2ave a nice day!\n')}

}




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include"stdio#h$void print_min(int - int y)

{if (- " y)printf ('min % d\n' -)

elseprintf('min % d\n' y)

}

int main (void){

int a b

printf('7nput a4')scanf ('d'5a)printf ('7nput b4 ')scanf ('d' 5b)

print_min(a b)return (,)

}

$(ample 4


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,uestion 0,uestion 0

rite a program to convert time torite a program to convert time to

minutes using function. rogramminutes using function. rogram

should allow user to enter the hoursshould allow user to enter the hours

and minutes and the time in minutes.and minutes and the time in minutes.


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Function with returnFunction with return

StatementStatement%he return statement is used to terminate%he return statement is used to terminate

the e(ecution of a function and returnsthe e(ecution of a function and returns

control to the calling function.control to the calling function.

A return statement may or may not returnA return statement may or may not return

a value to the calling function. Functiona value to the calling function. Function

can only return ) value.can only return ) value.

A function having void as its return typeA function having void as its return type

cannot return any value.cannot return any value.


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Function may return only 1 valueor no value

intmin(int a int b){

if (a"b)

return aelse

return b}

return a to main& a 'int(


StatementStatement


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int multiply(int -int y){ return (-8y) 98 can bereturn -8y 89}

int main(){ int answer answer % multiply(*,&,)

printf(The answer is d\n:answer)}

Prg50_FuncParameter.cpp


StatementStatement
http://prg50_funcparameter.cpp/http://prg50_funcparameter.cpp/


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include"stdio#h$int min(int a int b){

if (a"b)return a

elsereturn b

}

int main(void){

int 6 1 m

printf ('7nput two inte0ers3 ')scanf ('dd' 56 51)

m % min(6 1)printf ('\nThe minimum is d# \n' m)return (,)

}

$(ample 5


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int multiply(int -int y)

int main(){ int answer

answer % multiply(*,&,) printf(The answer is d\n:answer)}

int multiply(int -int y){ return (-8y) 98 can be return -8y 89}

Function %appen

after main ' (


StatementStatement


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6sing Functions:

include"stdio#h$include"math#h$ 98 contains s;rt() function89


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include"stdio#h$

int addTwoDi0its(int)int firstDi0it(int)int secondDi0it(int)

int main(void){

int number int sum

printf ('=nter an inte0er3 ') scanf ('d' 5number)

sum % addTwoDi0its(number) printf('Bum of last two di0its is 3 d\n' sum)

return (,)}

int addTwoDi0its(int number){

int result

result % firstDi0it(number) / secondDi0it(number) return result}

int firstDi0it(int num){ return (num *,)}

int secondDi0it (int num){ int result result % (num 9 *,) *, return result}

$(ample 5


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Function call by reference

Advantages:Advantages:

- provide greater time and space e7ciency- provide greater time and space e7ciency

1arguments are not copied into new1arguments are not copied into new

variables2variables2- function can change the value of- function can change the value of

argument in the caller.argument in the caller.

- function can return only ) value. f need- function can return only ) value. f needto return multiple values! pass theto return multiple values! pass the

arguments by reference so the values canarguments by reference so the values can

be modied in caller.be modied in caller.


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Function call by reference

include"stdio#h$


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