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CASE STUDIES

1. Processing of Examination Marks

Marks obtained by a batch of students in the Annual Examination are tabulated as follows:

Student name Marks obtained

S.Laxmi 45 6 !" 55#.S.$ao "% 56 6%

& & & & & &

't is re(uired to com)ute the total marks obtained by each student and )rint the rank list based onthe total marks.

*he )ro+ram in ,i+.--.-4 stores the student names in the array nameand the marks in the arraymarks. After com)utin+ the total marks obtained by all the students the )ro+ram )re)ares and)rints the rank list. *he declaration

int marks[STUDENTS][SUBJECTS+1];

defines marks as a )ointer to the array/s first row. 0e use rowptr as the )ointer to the row ofmarks. *he rowptris initiali1ed as follows:

int (*rowptr)[SUBJECTS+1] = array;

2ote that arrayis the formal ar+ument whose 3alues are re)laced by the 3alues of the actualar+ument marks. *he )arentheses around *rowptrmakes the rowptr as a )ointer to an array ofSU!ECTS"1inte+ers. $emember the statement

int *rowptr[SUBJECTS+1];

would declare rowptras an array of SU!ECTS"1elements.

0hen we increment the rowptrby rowptr"1 the incrementin+ is done in units of the si1e ofeach row of array#makin+ rowptr )oint to the next row. Sincerowptr )oints to a )articular row$*rowptr%&x')oints to the xth element in the row.

POINTERS AND TWO-DIMENSIONAL ARRAYS

ro!ram

#define STUDENTS 5#define SUBJECTS 4#include !"in$%&'

()in*+

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,c&) n)(eSTUDENTS./0.1in" ()2!STUDENTS.SUBJECTS3.1

in"f*6Inu" !"uden"! n)(e! 7 "&ei ()2! in f8u !u9:ec"!;n6+1

$e"in"f*6;n6+1in"

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?@ C8(u"e "8")l ()2! 89")ined 9 e)c& !"uden" @?

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c&) @"e(1

f8*i 1 i (-1 i33+f8*: 1 : (-i1 :33+

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,!))e)i. !i.1i331

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>>

"#tp#t

Inu" !"uden"! n)(e! 7 "&ei ()2! in f8u !u9:ec"!S%L)(i 45 HK 55%S%R)8 KK 5H HA%u") HH K 45S%M)ni H K/ 0 /5R%D)niel 44 55 HH KK

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R)n2ed Li!"

%S%R)8 KK 5H H /A%u") HH K 45 /KR%D)niel 44 55 HH KK /4/S%L)(i 45 HK 55 /05S%M)ni H K/ 0 /5

Fig.11.14Preparation of the rank list of a class of students.

(. In)entory Upating

*he )rice and (uantity of items stocked in a store chan+es e3ery day. *hey may either increaseor decrease. *he )ro+ram in ,i+.--.-5 reads the incremental 3alues of )rice and (uantity andcom)utes the total 3alue of the items in stock.

*he )ro+ram illustrates the use of structure )ointers as function )arameters. +item#the addressof the structure item# is )assed to the functions ,pate$% and m,-$%. *he formal ar+umentspro,ctand stock#which recei3e the 3alue of +item#are declared as )ointers of ty)e str,ctstores.

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STRUCTURES AS QUNCTION PARAMETERSU!in$ !"uc"ue 8in"e!

ro!ram

!"uc" !"8e!

,c&) n)(e/0.1fl8)" ice1in" Gu)n"i"1

>1()in*+,

F8id ud)"e*!"uc" !"8e! @= fl8)"= in"+1fl8)"

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"#tp#tInu" ince(en" F)lue! ice ince(en" )nd Gu)n"i" ince(en"0 /Ud)"ed F)lue! 8f i"e(

N)(e YPice 5%K50000u)n"i" /4

)lue 8f "&e i"e( 5%000000

Fig.11.15Use of structure pointers as function parameters.