CHAPTER 2

INTRO

DU

CTORY

CON

CEPTS

1

OUTCOMES:

Explain constants and variables

Describe data types

Identify operators in programming

Explain different between formula and

expression

2

VARIABLES

a meaningful name of data storage location in computer

memory

Variable’s characteristics:

• has a name

• has a type

• holds a value that you assign to the variable

3

CONSTANTS

are values that do not change during program execution

Types of constants:

• Integer constant

• Floating point constant

• String constant

• Character constant

4

RULES OF DECLARING VARIABLE & CONSTANT

• Variable names can be short as a single letter or as long as 31 character

• Names must begin with a letter of alphabet

• Variables only contain letters, numbers and underscore (_) character

• Variables cannot have same name as C command or function

• Variables can be formed by freely combining the letters, digits and underscore

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EXAMPLE:

Valid Invalid Comment

c “c” Illegal character

Totalx2 2totalx Illegal first character

Monthly_rate

Monthly-rate

Illegal character (-)

AGE AGE@ Illegal character @

SALARYPAY SALARY PAY

Illegal blank

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DECLARE CONSTANT & VARIABLES

Variables hold different types of data:

• Numeric (integer, floating point, double floating point)

• Character

• String

Variables can be defined in 2 places:a) After the opening brace of a block of codeb) Before a function name

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DECLARATION FORM:

Data typesVariable;

Typevariable_list

Example:

int no1,no2; int mark;char name[20]; float amount, rate;

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#include <stdio.h>int main(){

int a, b;int result;

a=5;b=2;a=a+1;result=a-b;

printf("\n\n\t\t%d",result);return 0;}

4

Output:

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Variables may be initialized by assigning constants to

them either at the time of their declaration or at a later

time

Syntax to declare a constant:

int days_of_week = 7;

data type variable value

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Example:

int m, n =10;char response = ‘n’; char color [6] = ‘green’;float rate, total = 0.0;

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#include <stdio.h>main(){char name[50], matrix[10];int date, month, year, age;int yearnow=2013;

printf("What is your name?\n");scanf( "%s", &name );printf("What is your matrix number?\n");scanf( "%s", &matrix );printf("What is your date of birth?\n");scanf( "%d", &date);printf("What is your month of birth?\n");scanf( "%d", &month);printf("What is your year of birth?\n");scanf( "%d",&year);

age = yearnow-year;printf("\n\n Your name is %s",name);printf (" with matrix number %s ", matrix);printf (“\n Your age is %d”, age);return 0;}

What is your name?AliWhat is your matrix number?1035

What is your date of birth?10

What is your month of birth?3

What is your year of birth?1990

Your name is Ali with matrix number 1035Your age is 23

Output:

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IDENTIFY THE SCOPE OF CONSTANT & VARIABLES

Integer constantare the whole numbers that do not contain decimal point

Example;

int number = 10;0, -708

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Floating point constanta decimal number that contains the decimal point (.)

Example;

float number = 0.7564;-12.0, 65.4

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String constant• always enclosed in double quotation marks (“

and “)• a single space, a word, or a group of words

between double quotation marks is a C string constant

Example;

char name[6]= “AHMAD”;“2.0”, “X”

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Character constant• should be enclosed within single quotation

marks (‘ and ‘)• all the alphabetic, numeric and special

character can be character constant

Example;

char numeric= ‘C’;‘X’, ‘0’

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KEYWORDS IN C PROGRAMME

• every word in C language is a keyword or an identifier

• keyword cannot be used as a variable nameDefinition Name Type

char Characterunsigned char Unsigned charactersigned char Signed character (same as char)int Integerunsigned int Unsigned integersigned int Signed integershort int Short integerunsigned short int Unsigned short integersigned short int Signed short integer (same as

short int)long Long integerlong int Long integer (same as long)signed long int Signed long integer (same as

long int)unsigned long int Unsigned long integerfloat Floating-pointdouble Double floating-pointlong double Long double floating-point

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DATA TYPES

Basic data types in C:• Integer• Character• Floating point• Double floating point

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INTEGER

hold whole numbers

Keyword : int

Syntax: int variable_name;

Example:

int number;int a, b, c;

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CHARACTER

hold only a single character

Keyword : char

Syntax: char variable_name;

Example:

char name[30];char huruf;

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FLOATING POINT

contain decimal points

Keyword : float

Syntax: float variable_name;

Example:

float value;Float gross_pay;

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DOUBLE FLOATING POINT

will ensure a maximum accuracy in decimal point

Keyword : double

Syntax: double variable_name;

Example:

double tax;double value;

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UNDERSTAND OPERATORS & EXPRESSION

• C math operators are symbols for multiplying, dividing,

• adding and subtracting and as well as for other

• operations

• are not always mathematical, but most of it is

• mathematical

• expression – combining operators, variables and

constants

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Arithmetic OperatorMost C programs perform arithmetic

calculations.

OPERATOR

ACTION ALGEBRAIC EXPRESSIO

N

C EXPRESSI

ON+ Addition f + 7 f + 7

- Subtraction p – c p – c

* Multiplication bm b * m

/ Division x/y or or x÷y

x / y

% Remainder or Modulus

r mod s r % s24

EXPRESSION

VALUE

a – b 5a + b 9a * b 14a / b 3a % b 1

Typical operator results. With a=7 and b=2, the expression on the values on the right

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Parentheses are used to group terms in C expressions in much the same manner as in algebraic expressions. For example, to multiply a times the quantity B+C, we write:

A*(B+C)

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Example:

ALGEBRA C

m= (a+b+c+d+e)/5;

y=(m*x) + b;

5

edcbam

bmxy

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Relational Operators

Operators for data comparisons are availableIt’s called relational operators, and the task is to compare data.

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Standard algebraic equality

operator or relational operator

C equality or

relational operator

Example of C condition Meaning of C

condition

Equality operators= == X == Y X is equal to Y≠ != X != Y X is not equal to Y

Relational operators> > X > Y X is greater than Y< < X < Y X is less than Y≥ >= X >= Y X is greater than

or equal to Y≤ <= X <= Y X is less than or

equal to Y29

Example:

if a = 7 and b = 5,

then a < b yields 0 and a != b yields 1.

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Logical operatorsThere may be times when you need to test more than one set of variables.

You can combine more than one relational test in a compound relational test by using C’s logical operators

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OPERATOR

MEANING

&& AND

|| OR

! NOT

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The first two logical operators, && and ||, never appear by themselves.

They typically go between two or more relational tests.

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a ba | | b

either a or b must be true

a&&bBoth a and bMust be true

! aProduces the

opposite relation

0 0 0 0 1

0 1 1 0 1

1 0 1 0 0

1 1 1 1 0

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Example:

The true and false on each side of the operators

represent a relational if test.

The following statements, for example, are valid if

test that use logical operators (sometimes called

compound relational operators).

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if ((a<b) && (c>d))

{

printf(“Results are invalid”);

}

If a is less than b, and c is greater than d, print results are invalid to the screen.

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if ((sales > 5000) || (hrsWorked > 81))

{

bonus = 500;

}The sales must be more than 5000, or the hrsWorked must

be more than 81, before the assignment executes.

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