10_-_specifying_comments_in_c.doc

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SPECIFYING COMMENTS IN C

Comments are messages that explains whats going on.

C comments beign with /* and end with */.

Comments can span several lines, and they can go just about

anywhere in a program.

Examples of Comments in C:

1. /* This is a singleline comment */

!. /* This is a comment that happens to span two lines be"ore

coming to an end */

#. "or $% & 1' % ( !)' %+ /* Counts "rom to !) */

CHARACTER ARRAY

-olds strings in memory n array is a list o" variables o" the same data type.

xample0

1. Char month12' /* de"ines a character array */

where0

[10]indicates that the maximum number o" characters the stringwill hold. The length o" the string is always the number o"characters up to but not including the null 3ero.

!. char month12 & 45anuary6'

/* de"ines a character array at the same time storing a string

value in the array */

month 2 12 !2 #2 72 )2 82 92 :2 ;2

J a n u a r y tring terminator


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where0

Subscripts are numbers speci"ied inside the brac?ets that re"er to

each o" the array elements.

Elementsare the individual piece o" an array.

String Terminator - C adds automatically the null 3ero at the endo" all strings.

INITIALIZING STRINGS

month & 4pril6' /* @AT BBAD */

String Copy Function STRCPY !"

assigns a new string to a character array

Eormat0

strcpy$char array, 4string6+

xample0

Finclude (stdio.hG

F include (string.hG

0

strcpy$month, 4pril6+' /* puts new string in month array */

0

PRINTING STRINGS

Hs "ormat speci"ier "or printing string array

Example:

1. print"$4The month is Hs6, month+'

!. print"$4


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hat is your "irst name= Jo$

hat is your last name= Harri%on

-ow old are you= &1-ow much do you weigh= #'(

-ere is the in"ormation you entered0

@ame0 5oe -arrison

eight0 !)

ge0 71

)EFINING CONSTANTS

Constants are data value that does not change.#definepreprocessor directive de"ines constants.

Eormat0Fde"ine CA@>T@T constant de"inition

xamples0

1. Fde"ine IB%J%T !1

!. Fde"ine JK@J 4Laula -olt6

#. Fde"ine L% #.171);

E*$rci%$ 1+

rite a program that will prompt the user to enter his "irstname,

lastname, age and weight. Then the program will display the name

$"irstname and lastname combined, age and weight+. Melow is the

sample execution o" the program0

,


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Pr$c$-$nc$ an- A%%ociati.ity o/ Op$rator%

ans & ) ! * #' /* puts 11 in ans */

The "ollowing summari3es the rules o" precedence and

associativity0

Op$rator% A%%ociati.ity

$ + $post"ix+ $post"ix+ le"t to right

$unary+ $unary+ $pre"ix+ $pre"ix+ right to le"t

* / H le"t to right

le"t to right

& & & *& /& etc. right to le"t

xamples0

ans & ) ! * 7 / ! H # 1 N #' /* hat is the answer= */

avg & ! # 7 ) / 7' /* will @AT compute the averageO */

ans & $) !+ * #' /* puts !1 in ans */

avg & $! # 7 )+ / 7' /* puts !1 in ans */

&

Example

a+ ! * ) ) * # 7 * 1& 1 ) * # 7 * 1

& 1 1) 7 * 1& 1 1) 7

& !) 7

& 8)

b+ 7 H ! # 7 * )

& # 7 * )

& # !& 19

c+ 9 a * bwhere a & ! and b & 7

& 9 $!+ * b& 9 $!+ * $)+

& 9 $1+

& 9 1

& 19


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a = ++age;

ssume age = !.

"ter execution o" this statement, a = "and age = ".

a = age++;ssume age = !.

"ter execution o" this statement, a = !and age = ".

CAJLAQ@D >>%I@J@T

x & x 1' /* adds 1 to x */

sales & sales * 1.!)' /* increases sales by !)H */

x & 1' /* adds 1 to x */

sales 4 15#(6 7increases sales by !)H */

Compoun# $ssignment %perators

Compound xample Puivalent >tatement

Aperator

*& total *& 1.!)' total & total * 1.!)'

/& amt /& "actor' amt & amt / "actor'

H& days H& #' days & days H #'

& count & 1' count & count 1'

N & adjust N & .)' adjust & adjust N .)'

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