05 es26 lab - data types

8/14/2019 05 ES26 Lab - Data Types

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Introduction to Programming

Basic Data TypesBasic Data Types

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Fundamental Data TypesFundamental Data Types

DATA TYPE SUGGESTED USAGE

char Text characters such as 'a','b','@' and so on

int Integral numbers such as 1, 2, 3, and so on

float Low/medium precision real numbers

double Medium/high precision real numbers

Adata type defines a set of values and aset of operations that can be performed onthose values.


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Their respective sizes are not strictlydefined by the standard.

The compiler vendor selects the mostappropriate size that suits thearchitecture of the host computer.

Hence, compiler- and machine-dependent


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Both char and int data types store integralvalues.

Get actual size in bytes of any data type byusing the unary operator (not a function)sizeof.

...

char ch;

printf( %u, %u, sizeof ch, sizeof(float) );

...

Unsigned intparenthesized


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DATA TYPE VALUE TYPICAL SIZE

char Character 8 bits

int Integer 16 bits

float Real number 32 bits

double Real number 64 bits


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The Integer Data TypeThe Integer Data Type Keyword: int

Represents whole numbers in C

Its values typically range from 32768to 32767 (16 bits)

Here are some example of integers:

13, -214, +2001, 2002

An int cannot contain commas. Forexample, 2,001 is not a valid integervalue


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The Integer Data TypeThe Integer Data Type

signed (default) 16-bit int

0000 0000 0000 0000 = 0

1000 0000 0000 0000 = -32 768

-32 768 to +32 767

Sign bit (1 for negative) 15 bits


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unsigned 16-bit int

0 to +65 535

Whole 16 bits


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Care must be taken with signedquantities to ensure that any

arithmetic operations such as additionor subtraction do not generate anover- or underflow

Incrementing 32 767 will result to achange of sign when using signed 16-bit int


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Type Modifiers for IntegralType Modifiers for Integral

QuantitiesQuantities short int


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Type Modifiers for IntegralType Modifiers for Integral

QuantitiesQuantities The following are the '%' format

indicators recognized by scanf()

'%' formatter Appropriate

data type(s)

Input recognized in following

format

%d, %i, %u, %x, %o int Decimal, decimal, unsigned

decimal, hexadecimal, octal,

respectively

%ld, %li, %lu, %lx, %lo long int -same as above-

%hd, %hi, %hu, %hx, %ho short int -same as above-


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Real Number Data TypeReal Number Data Type

Both float and double data typesrepresent a real number in C

A float consists of an optional sign (+ or-), followed by one or more digits, adecimal point and one or more furthernumbers.

A double is a special float, which canstore more significant digits.


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Represented as floating-point numbers.

We often use scientific notation to

represent real numbers. In Math, 1.23 x 105 = 123000.0

In C, 1.23e5 = 123000.0


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Here are some invalid examples of realnumber in C.

0.1234e /* missing exponent */

15e-0.3 /* invalid exponent */

34,500.99 /* comma not allowed */

150 /* no decimal point */


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MantissaExponent

Typical representation of a 32-bit float

Sign bit

31 22 0Bit number


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MantissaExponent

Typical representation of a 64-bitdouble

Sign bit

63 51 0Bit number


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Type Modifier for Real Number Data TypesType Modifier for Real Number Data Types

float


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Format IndicatorsFormat Indicators

For the printf() function

'%' formatter Appropriatedata type(s)

Output format

%f Float or double Floating point format

%e Float or double Scientific format

%g Float or double Shortest of '%f' and '%e'

%Lf, %Le, %Lg Long double Floating point, scientific, and

shortest of '%f' and '%e',

respectively


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Format IndicatorsFormat Indicators

For the scanf() function

Format indicator Input format

%f, %lf, %Lf Floating point or scientific format for

a float, double or long double,

respectively

%e, %le, %Le -same as above-%g, %lg, %Lg -same as above-


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The Character Data TypeThe Character Data Type

Keyword: char

A char is a letter, digit or symbol

enclosed in single quotes. Here are some examples of characters:

c S 2 $

Note that the space ( ) is a characterjust like any letter or digit


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Some non-printing and hard-to-printcharacters require an escape sequence

They consist of a backslash ( \ )followed by a character.

For example, a horizontal tab is

represented as \t when used in a Cprogram.


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Name of Character Escape

Sequence

Alert \a

Backslash \\

Backspace \b

Carriage return \r

Double quote \

Some Non-printing characters


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Data TypesData Types

More on Data Types next time :)


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Variable Declaration andVariable Declaration and

DefinitionDefinition Declaration is used to name an object

like a variable

Definition is used to create objectsand reserved memory space.

Syntax:


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Variable DeclarationVariable Declaration

C allows multiple variables of the sametype to be defined in one statement

Example: int height, width;

char choice, index;Variables can be distributed among

declarations in any fashion.

Example:char choice;char index;

int width;

int height;


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Variable InitializationVariable Initialization

A variable may be initialized in itsdeclaration

Example: int height = 10, weight = 20;

char choice = Y, index = a;

the expression on the right serves as aninitializer


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ConstantsConstants Constants are data values that cannot be

changed during the execution of aprogram

Aliteral is an unnamed constant used tospecify data

Example: c /* a character literal */

5 /* an integer literal */ 3.1416 /* a float literal */

Hello /* a string literal */


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Explicit ConstantsExplicit Constants

An explicit constant is introduced in muchthe same way as a variable, but with its

definition prefixed by the word (or typequalifier) const.

They should be initialized during definition.

...

const float pi = 3.14159;

...


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Preprocessor ConstantsPreprocessor Constants

Another way to designate a constant isto use the preprocessor commanddefine

Syntax: #define

A#define statement allows you togive names to constants

A#define statement allows you togive names to constants


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Named ConstantsNamed Constants

Example:

#define PI 3.1416

#define EXCHANGE_RATE 52.50

The action of #define is just like thesearch and replace command found in

your text editor

No semicolon


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Input/Output FunctionsInput/Output Functions printf() function - general purpose

output routine

Format: printf(, item1,

item2); In its simplest form, it can display a string of

characters enclosed in double-quote marks onthe screen, as in:

printf("You made an error - try again!\n");


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Input/Output FunctionsInput/Output Functions

Controlling the Format

%d - decimal integer.

%f - float.

%lf - double

%e - float in 'exponent' form, eg 1.23E+02 ( E+02 means ten to power +2.)

%c - single character.

%s - character string.


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Input/Output FunctionsInput/Output Functions

scanf() general-purpose outputroutine

Format:

scanf(, addr1, addr2);


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Arithmetic OperatorsArithmetic Operators

C supports the arithmetic operators:

+ Addition

- Subtraction

* Multiplication

/ Division

% Modulo


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Examples:

A = 2 + 3;

B = 2 3;

C = 2* 3;

D = 4 / 2;

E = 5 % 2;


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The modulo (%) operator computesthe remainder of an integer division

For example, 5 % 2 is 1 because 5divided by 2 is 2 remainder 1.

Moreover, 11 % 2 is 1 because 11

divided by 2 is 5 remainder 1.


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Floating Point Arithmetic

C requires that in a quotient A/B, the

denominator, B, must be nonzero

Division by zero will cause a programcrash that is why it should be avoided


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Integer Arithmetic

The quotient of 2 integers is not

necessarily an integer.

For example, the quotient 3/4 equals afloating point number 0.75, which is not

an integer.


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Integer Arithmetic

If you divide an int by an int, the value

you get will be truncated or roundeddown to the largest whole number lessthan the result

For example, 10/3 = 3 and 3/4 = 0


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Unary Plus and UnaryUnary Plus and Unary

MinusMinus The unary plus (+) operator causes no

change to the quantity that follows

where the unary minus (-) operatorcauses the sign of the followingquantity to be changed.

Examples: +5 -5


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Assignment OperatorAssignment Operator

A statement that assigns a value to avariable is called an assignment

statement and has the format:variable = expression

Example: y = 21;

Ch = A;x = (2 + 5) * (10 6);

net = gross expenses;


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Expression Equivalent

k = k + 2; k += 2;

k = k - 2; k -= 2;

k = k * 2; k *= 2;

k = k / 2; k /= 2;


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The semantics is specified by

variable op= expression

is equivalent to

variable = variable op expression

The left side of the equal sign should bea variable, not an expression

Thus, the statementx + 2 = 0;

is not a valid statement


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Precedence and AssociativityPrecedence and Associativity

Precedence is used to determine theorder in which different operators in a

complex expression are evaluatedAssociativity is used to determine the

order in which operators with the same

precedenceare evaluated in a complexexpression


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Operators Associativity

-- ++ - (unary) Left to right

* / % Left to right

+ - Left to right

= += -= *= /= Right to left


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Example: The expression 1 + 2 *3 isequivalent to 1 + (2 * 3)

Expressions inside parentheses are

evaluated first Example: The expression 1 + 2 3 + 45 is equal to 1 based on the left-to-

right rule of associativity Thisexpression is equal to

(((1 + 2) 3) + 4) 5


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The unary operators have higherprecedence than the binary plus. And

minus In the expression a * b c, the firstminus is unary and the second is binary.

Using the rules of precedence, we seethat the expression is equivalent to

((-a) * b) c.


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Type ConversionType Conversion

Implicit type conversion happenswhen C automatically converts a type

from one format to another. For example, the expression in the

statement x = 2 + 3.5 will evaluate to

in integer value if x is an integervariable.


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We can actually force the conversionprocess to take place

This is called explicit typeconversion and is done with a unaryoperator called a type cast.

Format: (data type) expression


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The type cast causes the value of theexpression to be converted to the data

type. For example,(float) (10 + 2)

evaluates to a floating point number,

12.0

05 es26 lab - data types

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