MELJUN CORTES C++ Chap4 Data Types Variables Expressions

8/10/2019 MELJUN CORTES C++ Chap4 Data Types Variables Expressions

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A Closer Look at Data Types

Variables and Expressions

C Programming Language


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MELJUN CORTES MBA MPA BSCS

School of Computer I nformation 2

Objectives

Well learn Data type modifiers

Global/local Variables

Constants Type conversions


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1. Use Cs Data-Type Modifiers

Type Modifiers char, int, float, double can be modified using Cs

type modifiers to more precisely fit your specific

need.

signed : apply to charand int, default.

unsigned : apply to charand int.

shot : apply to int.

long : apply to intand double.


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(4 byte)

(8 byte)

(10 byte)(4 byte)

(2 or 4 byte)

(2 byte)


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All Data Types

char 8 -128 ~ 127

unsigned char 8 0 ~ 255

signed char 8 -128 ~ 127

int 16 -32,768 ~ 32,767

unsigned int 16 0 ~ 65,535

short int 16 -32,768 ~ 32,767

unsigned short int 16 0 ~ 65,535

long int 32 -2,147,483,648 ~ 2,147,483,647

unsigned long int 32 0 ~ 4,294,967,295

float 32 3.4E-38 ~ 3.4E+38

double 64 1.7E-308 ~ 1.7E+308

long double 80 3.4E-4932 ~ 1.1E+4932

Data type Bits Range


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Shorthand notation (implied int) unsigned int unsigned

short int short

long int long

Format specifiers of printf() & scanf()

%hd - short int

%ld - long int

%u unsigned

%lu - unsigned long int

%Lf - long double


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Example 1. How to input and output shot, long, and unsigned values.





Example 2. The difference between the way that signed and unsigned

integers are interpreted by C.

**** Result ****

-32536 33000





Example 3. Using a char variable for number arithmetic.





Exercises

Write a program that prompts the user for a distance and

computers how long it takes light to travel that distance.

Use an unsigned long int to hold the distance.

(Light travels at approximately 186,000 miles/sec)

====== Light travel time computation program ======

How long distance (miles) : 500000

500000 miles => 2.69 sec.




2. Learn where variables are declared

Location of variables declared

Inside a function local variables

Outside all functions global variables

Local variable

Is created upon entry into its function

Is destroyed upon exit

Can use the same name in different functions





#include

void f1(void), f2(void);

int main(void) {

f1();

return 0;

}

void f1(void) {

int count;

for (count=0; count





The Scope of local variable





The Scope of global variable#include

void f1();

int max; /* global variable : entire program validate */

int main(void) {

max= 10;

f1();

return 0;

}

void f1(void) {

int i;

for(i=0; i




Example 1.

A local variable and a global variable may have the same

name.


**** Result ****

count in f1() : 100

count in main() : 10




Example 2. - Appropriateness using of global variable.





Example 3. - Local variables dont maintain their valuesbetween functions calls.






Exercises

Write a program that contains a function called soundspeed(),

which computes the number of seconds it will take sound to

travel a specified distance.

Write the program two ways: first, with soundspeed()as a non-general function and second, with soundspeed()parameterized.

(For the speed of sound, use 1129 feet/sec)

====== Sound travel time computation program ======How long distance (feet) : 5000

5000 feet => 4.43 sec.




3. Take a closer look at constants

Constants Fixed values

Integer constants

100, -65, 0

Floating-point constants

11.123, .501, 123.456E1

Character constants

Z, =, \n

Numeric constants Make decision the data type

10 int64000 unsigned

100001long

123.25 double





Constants Make decision of the exact type by using suffix

Floating-point types

F float,

L long double

Integer types

U unsigned,

L long

A Number system based on 8 :octal

9 011,

21 025

A Number system based on 16 : hexadecimal

26 0x1A, 13 0xD





Constants String

A set of characters enclosed by double quotes.

Format descriptor : %s

#include

int main(void) {

printf ("%s %s %s", "Once ", "upon ", "a time");

return 0;}


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Example.

You may need to explicitly tell the compiler what type of constant

you are using.

It does not output the correct value.

You need change type of constant

2309 2309.0


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4. Initialize variables

Variable initialization

Initialization of global variable

Using Only constants

Initialized only once at the start of program execution.

Initialization of local variable

Using constants, variables, or function calls

Initialized each time a function is entered

type var-name = constant ;

int count = 100;


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Example 2.

Local variables are initialized each time the function is

entered.


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Example 3. - Initialization by any expression


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Exercises

Write a program that gives an integer variable called ian initial

value of 100and then uses ito control a forloop that displays

the numbers 100down to 1.

int i = 100;for( ; i > 0 ; i--)

printf(%d , i);


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5. Understand type conversions in expressions

C lets you mix different types of data together inone expression.

char ch;int i;float f;

double outcome;

ch = '0';i = 10;f = 10.2;

outcome = ch * i / f ;

int type

float type


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Examples of implicit conversion in expressionsExpression Intermediate Type

char + float

int long

int * double

float / long double

(short+ long)/float

float

long

double

long double

long then float


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Type promotion


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Example 1. - implicit type conversion


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6 Understand type conversions in


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6. Understand type conversions in

assignments


1234.009800 1234

6 Understand type conversions in


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6. Understand type conversions inassignments

Exercises - What does this program display?

Result 3.000000


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7. Program with type casts

Type conversion using type casts Transform the type of a variable temporarily

Can use only right side of assignment statement

(type) value

float f;

f = 100.2;

/* print f as an integer */

printf ("%d", (int)f);


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7. Program with type casts

Example 1.

Use sqrt(), for loop

Print the square roots of the numbers between 1 and 100.

Print the whole number portion and the fractional part of

each result separately.


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MELJUN CORTES C++ Chap4 Data Types Variables Expressions