Test Your C Skills

129 Pages·2006·59.64 MB·English

Contents

Introduction
Declarations an Initializations
Control Instuetions
Expressions

Flowing Point Issues

Functions

‘The C Preprocessor

Pointers

‘More About Pointers

Amys

Strings

Structates, Unions and Faumerations
InpavOuput

‘Gonumand Line Arguments
ptwise Operas

Sublletes of npedlef

“The cones Phenomenon
Memory Allocation

‘Variable Number of Arguments
Complicated Destoraions
Liveary Functions

wv

169
1

231

Introduction

“There is no dearth of goud C programming books im the market
However [found that there is mot much material which could help a
(C programmer to res his programming sttengts, help improve his
‘ponfidence and inthe pracess hone his (skis. Hence this book

‘This is not text Book om C. Infact tis far Feom

Tteontsins alot ot questions segreyated topie-wise ascardtg to my
perception ofthe larguage, Almost all the questions ae real one's
Asked by real people llempting to Tear or program in C,

“Thore is no reason why you should read the questons in the same
border es they appear in ‘his book. You can pick pany topic tht you
think you are good at (or poor at} an try to test your skills on that
topic.

“There isa good chance that you ate earning a vsing C and you
hheve questions abput that aren'tanswered in any ofthe ether books
you'vechecked, you woud find hem ansroted here. Itwouldbe too
Toeh to expect that you world find in this book answer 10 every
{question you would have when you're progeemming in C. This is
Because many of the questions that may some up in yrur program
ming sould have to do with your problem domain, whereas evs bok
Concentrates only on the C language, Also it docsn’s enver every
aspect of every operaling system under whic’ C isrunm ny, Problems

vecifc to nn operating systems, and ponera purpose elgorishms ae
proper y discussed in hooks devated io those tape.

At the end of each ehaprer you would find correct answer to the
{questions in that chapter, You would tind some answers more
Claborate than oshers. AL fist sight this may seem unnecessary
However, [lave done this to give you the complete pictute rather
than oversimpiitying or Ieaving wut important detail.
have tiv w avoiu the questions whose answers ane ron. obvious
beens the idea sas nt fo increase the nummer questions, but tO
present.questiors winch wold oroe the readers tink wre before
answering, That sin tune withthe spirit oC he presse, bceviy bas

its own importance. Chapter 1

Soroll your sleeves und get on with eve real cuestions, Good lush! Declarations and Initializations

‘Yashavant P. Kanetkir
Nov 1996

Qu

‘What would be the output 3 eFotewing progeaun?

(
charfar‘st*62;
Dent "ed size st, siomt <P })

Qn

‘What would ke the ouspu of the Flowing program?

ints = 4
Prin
{
intx=20;
print (“tse x)
}

Qs

What would be the nut ofthe following program?
, <a

2 2 Test Your € Skills Chapter 1: Declarations ont! fnitialisulons 3
nh)
te Q is
Tsiluuetata global viable ny have several dearatensbacenly
ne defttiion? <YexNe>
paint) Qu
Isitrme hot frien may have saver decratons, but only ne
Qu definition? <Yes!No~
Icha follwing minersena declaration ora eke anuen” Q 18
oni Inthe fllovirg program wheres tac vial u geting Uefined and

‘wheres it geting dec-arod?

Qa rain)

5
‘Whar would he the output ofthe fallosing program! extominta.
rin (ic
mmsin() }
ina=20;
ext it;
120: @ 19

rine sizgot (1)

What wom be tke ouput ofthe folosying progearn?

eo
a 4 main’)

©. Would vary from compiler to compiler

1D. Eiror, (defined extom inca;

pai nr a)
)
naz;
3 ‘ost Yur € Skil

mn
a

Garbage vulus
Enor

a
8
©
D.
Qs

What's the difference between a defintan und declaration of
varie?

Qu

Itghe definidon oan exter! variable uceurs mthe source tle before
its use m x particular function, then there 1S ne noed for an extern
slecluaticn inthe Function, «TsuctFalse>

Q in

Suppose program is divided irto three files), 2 aud al
‘variable is defined i le ile? hue used in the files 2 anf. n seh
«4ease would We need the external declaralion for ‘he variables the
files andj3?-<y estNo>

Q us

When we mention the protarype of a function are we definin
funatian or devlaring i?

Q i

‘What's the uifference between the following declarations?

2.

Chaptor 1: Declarations ona hi

oem int fin}
ietun()

Q us

Why Hoes th
Futon ig

Fopeet a redeclaraion enor bY

(
splay)

‘Wiha would be the output of te Following progr’?

ain)
‘
cota tun fat}
ita;
atin 344);
pei (a
'
tun}

relur {{ int) aa
6 est Your C Sills

3
344
a
Enor

Poin out the errr, ifany, in the Following program.

smuctemp
chat nae
intoge;
1
7 some meso cade nay goer"
fun( ita}
‘
ino:
=a"
retum bb);
)
slo)
t
ina:
aziin(20);
inf ("WC 8);
)

Chapter I: Declarations and initiatisations

Q us

Tf you are to share the varies or functions across several souroe
files haw would you ensure tht all definitions and deckarasions are
ceansisere?

Q 129

‘How would you reetity the error in the following program?

{fstuct emp);
any cher proltypes may oo here"
fmt emp

charroms[20);
Intage

sructor = {“Soicher’ 34);
te);
}

${etue omp 00)
i

Q 120

Glohal variables are available to all functions. Does there exist a
mechanism by way of which Ian make it wvalable to some and not
tw others

rn, ks "e" e:name, 02.98 5
Pont tate (Sit (Chapter 1: Declareions and Iniiatisations 9
A 0.900000
fee oc ae Garbage values
‘What eo you mean ba trstation mnt eo
D. None af euhove
Q 12
Q 124
Wher weold bee oulpu ot folowing poate?
ae Some books suggest chat the ollnwing definitions shone
\ preceded by the word state Tse core
Wr ie aoa intel] (2,3, 4, 12.02
i 55, of 3. stuctemp e~("saney", 23)
A. Garbage valucs Q wos
Bb 2a3
ins2'2 pint ou the coi aay, he Following program
See Point out the enor. if any nthe following progran

maint)

Q ix {

in(*9 ) =tuns

‘Wheat would be the output th following progra ae
fun)
rn t
sired wg oo
charrama(2] 7
tage * Q 126
float sal
iH Point out be eror, if any, inthe Following prograte

shuctempe= ("Tiger }
Pi "nsieP, e299. o.el] an)

(
i se esas eet est Your © Skil
ini
cha’ ef
}
urionaz=812
prin “Ld eh, zeh] Ss

Q wr

‘What do you mean by scope of a variable What ere the 4uiffereat
types of scopes that a variable cam have?

Q 128

‘What are the differenc types of inkages?

Answers.
eet
a2
A 12

20. Whenever there isu conflict between a local variahleand a global
Satiabe it isthe local variable which gels a privity

ons aud lnitatiations Ht

20 40. Incase of a cantict between local vatiaoles, the one whichis
‘more local that gets The priority

Aw

Declaration

A is

extern inv iis wdeeleation and not x definition, hence the eer.
A i6

Yes

Aw

Ves

A 1s

{ektern int cis the declaration whereas i.

A 19

10s the definition.

A
2 ‘os Your € Skills

A 1

Inthe definton of a variuhle space is reserved forthe variable andl
sonic inital values given tole, whereas coslaration only identifies
the type of the variable Fors Function. Taus definition isthe place
"aor te varahle iscrcatod orassigaed storage whorees declaration
referto places where raturcal the variable slated bueno storage
isallocate.

We are deeiaring il. Wha the fonction alongwith the statements
belonging to iare mentioned we are defining the Function,

Ai ou

“There leno difference except forthe fact thatthe fis one gives. bint
that te fonction fund) is probably in unolbe: saute file.

A165

Hore display jis called betore:tis defined. In such
assumes thal the functor display is declared ay

Chapter 1: Declarations and tnialisasions

int spay):

‘That is, n undeclared Fonction is assumed to setuinan int aud aoe
an unspecified mumber of arguments. Then when we define the
‘onction che compiler finds hat tisreursing void hence tre complet
report the discrepancy,

A 16

, The enorocenrs bovause we have mixed the ANST ps
K& Rotyle of fusction definition,

ype with

Wien we use ANSI protptype fora funesion and passa leut tothe
fantion itis prennoted ty a double, When the fonetion accepts this,
douse into afloat a ype mismatch occurs hence the errr

The remedy for ths ewor could he to define te fonction as

intun (feat 29}

i
}

Aiur

Revaure af she missing semicolon atthe end of the structure deela-
fution (ihe intervening comment further abscures if) the couupiler
believes ts fant! would reuur sorneting ofthe the ty30 struct em,
whoress in acua ity vis avempring to rete ar int. This causes a
mismatch, hence an ercor results.
7 ‘Test Your € Skits

(Chapror 1: Declurutions ene Initiatisations is

A i

‘Te best arrangement is place cach definition in relevant efile
‘Then, gut an extemal declaration in a header file (h ile) and uso
inlaw bring inthe deleration wherever needed.

‘The .¢ file which contains the definition should alsa include Ge
Ineader ile, o thal the compiler san check Ihat the definition matches
the declaration,

Declare the structure before the prototype off
A 120

'No. The ouly way this canbe achieved ist define the variable Locally
in main) snstead of defining it globally and then passing it wv the
Tunetions which need it

A 121

‘A teanslacon gait isa set of source Miles seen hy the compiler and
translated ara unit: generally one file, plus all header files men
‘oned in include directives.

A 12

D. When an automatic array is partly initialised, the remaining
aay clement ae niilisedt00.

A 123

A. When un autonsatie stuctone is patally iia ise, the remaining
Clemens ofthe structure are initalisod 0.

A 124

Pre-ANST C compilers had such ¢ requisemsnt, Compilers whic
‘Son’orm co ANS! € standard do no: have such x requirement

A 125

Tere we are iniiatising tho function pointer p tothe adress of the
function vi. Bul during thisintialsation the function has noc heen
defined. Hence an ercor

‘To eliminate this enc add the protoryps ofthe funt} before declara-
lion ofp, as shown belov:

‘eden int):
orsimply
inting);

A 126

Ina pre-ANSI compiler a uni varlable cannot be Intallsed. How-
cf, ANSI C permits imualisation of first memeber ofthe union.
16 est Your (kills

A 127

‘Scope indices the region ever whieh the varable's declaration has
an effect, The Four kinds of scopes arc’ file, funetion, Rluck and
proioype.

A 128

Trore arw three different types of linkagess external, internal and
‘one. External inkage means global, no-satc varies an fune-
Uns, internal Linksge mans static variables and fonctions with le
Scope, ad no linkage means local variables.

Chapter 2

Control Instructions

Qx

‘What would be the ouput ofthe following pragrarr?

bata
print nf mauseieanelpant but 2y te Jaserese!
9601
pint “needing abi share aling expe

‘sat

hen raed

Q 22

Point out the errr, 1 any, nthe fo" loop.