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SLLdi,- Today's Topics i n Creating Functions - How to define e function - Ca[ling a function 1 Loeal varrables - Seope ofa lecal varsable t Use global vartables 1 declering a g[obal vanable - Scope ef a g)obal vanable - Arrays as global variables

1 1 #lnclude (stdlo h> fYpe-of-functton Name(Parameters){ Oescrtpt2on returz Ret=rn.value, fkGwe the return valae ot this functien*/ } int main(veid){ deuble a; a = "ame(Parameters); /*Cal1 to the functlon "ame*/ } -diL 1 N 1 N t N 1 Each function has Parameters and Retutn value, Define a functfon before #mclude stntement after main function (Nft)u can use the funct-on after you cief-ne it ) Funct-en name should not be the same as reserved words Funct)ens exit wtth the return statement Multi parameters are acceptecl but the return value should be ene When we cal[ a funct-on, ass)gn Parameters te the funct)en and get a return value

kL l 1 1 1 =bLL/ lo;Lveilra: maln(vold>{ deuble a[3] a[O]=2 5*Of! a[1]=2 5*t+i a[2]=2 5*2-! return O; Avoid N"1infi o; o o m)ny Ltmcs the comf"on pJrts '!5p LO" i 1

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vX- More remarks on functions 1 N AII programs of C language eonsist of functiQns J xnt matn(veid){,,,} is also a functien, - Every program need the rnatn function l fypes ef functtons - ma)n function (called at the begtnning of the program) - Standard functions (with #inelude statement) - Functdons for obtalndng the return value (ex sm(x), log(x)) - Operetions in the functions with ne return vaiue (ex printf(''Hello, worldNn`'), etc ) l Why making functions7 - Functions allow us to group commonly used code inte a cemnect - We cen write e progrem in units easy to understend unit i

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s vL- A hint of exercise i / N Ybu make a functien max(a, b) that returns a btgger va[ue of a ancl b We ca[1 thts function in the matn function, 1 double max(double a, deuble b){ if Ca statement is needed, (2) -im option ls necessary / /

s 1 / / A hint of exercise Here ts an example of the main function the mein functien int main(void){ double x, yd Pnrrtf("Znput x:ii) scanf('dXl±",ex) y max(x, -x) Y Max(Y, XIX) prmtf("Answer retuTp O; } l - - im",y) A variabie x is an lnput value The y is assigned a temporary value of the maximum Call the max functien repe2teclly and assign e2ch return values to y -diL

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i / / 1 Parameters and Variables N When a value of the parameter is changed in a functien, the input value is never changed Ln the main functJen " Nbu can cleclare a vanable of the same name in dtfferent functions but these are considered as a dlfferent thing #mclude vozd func"nt x){ /* x x=7, !* The } mt main(void){ !nt x=3, tunc(x>, 1* Paraneter x pnnti("'x ls Xd.linL x); return O; } is deelared only in thzs function *1 x belew zs dlfferent :rem thls x, *f :s 3 and copies 3 te the x above, *1 1* Here "x is 3,'' *1

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s 1 1 1 Scope of variables 1 The scope of a varlab[e ls the area of the program ln whTch the vanable is valid N A local vanable (includtng parameters) has e scope that is limited to the function in which tt is declared - Ybu can declare a local vanable wtth the same name as anether lecal variable in a different functton, These are consiclered as different, double ±unct±onA } :nc funct:enB(xnt deuble y, } (mt x, irrt y){ /i The scepe e± x and y. +1 xi{ /lp Tlie scepe e± x ana y. *1 i

"LLL- Global variables =>A globa] var-able ss valid everywhere, so its scepe ts the who[e l Declared outside of functtons (usually after #melude or #dehne statement) - Scope entlre program 1 / progrem #mclude double ParamA, ParetuB: /. 1, Glebal variables sk1 deuble XinearCdeuble x){ return ParamA*x+ParamH; f* 3. Global can be used here- *1 } lnt maln(vold){ ParamA=5 0: Pa:amH=3 2: ls 2 Ass:gned values t/ p:int±C'"Result zs X±,fu'". Iinea:(1 2)): pnnt±("Result is X±,IEn", lmeaT(2,O)), retum O, } i

s VtL- Arrays as global variables 1 / Huge arrays must be declared as global variables ex mt main(void){ double Array[2000000000] !* Huge array camot declere - - Arrays as glebal variables are instialized all The huge array is net recemmended unless double Array[2000eOOOOO] = {1.0, 2.e}; o it arrays, , ts nece$sary /* Ne way.,. */ i

s "VLL- Examples of functions 1 : / 1 1 int methodl(mt a, int b) - Parameters a, b Ctype ef lnt) fype of return value znt doub!e methed2(int a, deuble b) - Parameters a, b (type ef int and double respectweiy) TYpe of return value, denble boolean methed3Cint a, ini b, int c) - Parameters' a, b, c (type of int) fype ef return value blDolean (true or talse) void method4(double x) - Parameters' x {type ef double), fype eF return value nbne double methed5(vetd) - Parameters, none, 1lype of return value, deuble i

,,llll)Ui---- Summary -dik.- 1 N Creeting Functions - How to define a functton - Calling a function 1 Loeal vamables - Scope ofa local vanable t Use global vartables 1 declaring a g[obal vaneble - Scope ef a glebal vaneble - Arrays as global variab]es