05 Es26 Lab - Data Types

Basic Data Types 5

Introduction to Programming

Fundamental Data Types • A data type defines a set of values and a set of operations that can be performed on those values. 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 Introduction to Programming

Fundamental Data Types • Their respective sizes are not strictly defined by the standard. • The compiler vendor selects the most appropriate size that suits the architecture of the host computer. • Hence, compiler- and machinedependent Introduction to Programming

Fundamental Data Types • Both char and int data types store integral values. • Get actual size in bytes of any data type by using the unary operator (not a function) sizeof . parenthesized

Unsigned int

... char ch; printf( “%u, %u”, sizeof ch, sizeof(float) ); ... Introduction to Programming

Fundamental Data Types 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 Type • Keyword: int • Represents whole numbers in C • Its values typically range from –32768 to 32767 (16 bits) • Here are some example of integers: 13, -214, +2001, 2002 • An int cannot contain commas. For example, 2,001 is not a valid integer value Introduction to Programming

Type Modifiers • Modifiers such as signed, unsigned, long and short are used to alter the meaning of data types to fit the needs of various situations more precisely

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The Integer Data Type • signed (default) 16-bit int • 0000 0000 0000 0000 = 0 • 1000 0000 0000 0000 = -32 768 Sign bit (1 for negative)

15 bits

-32 768 to +32 767

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The Integer Data Type • unsigned 16-bit int Whole 16 bits

0 to +65 535

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The Integer Data Type • Care must be taken with signed quantities to ensure that any arithmetic operations such as addition or subtraction do not generate an over- or underflow • Incrementing 32 767 will result to a change of sign when using signed 16bit int Introduction to Programming

Type Modifiers for Integral Quantities • short int <= int <= long int • The following are the '%' format indicators recognized by printf() '%' formatter

Data type(s)

Output displayed in following format

%d

char, short, int

Decimal

%x

char, short, int

Hexadecimal

%o

char, short, int

Octal

%u

char, short, int

Unsigned decimal

%ld, %lx, %lo, %lu long int

Decimal, Hexadecimal, octal or unsigned decimal, respectively

Introduction to Programming

Type Modifiers for Integral Quantities • 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 Type • Both float and double data types represent a real number in C • A float consists of an optional sign (+ or -), followed by one or more digits, a decimal point and one or more further numbers. • A double is a special float, which can store more significant digits. Introduction to Programming

Real Number Data Type • 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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Real Number Data Type • Here are some invalid examples of real number in C. • • • •

0.1234e /* missing exponent */ 15e-0.3 /* invalid exponent */ 34,500.99 /* comma not allowed */ 150 /* no decimal point */ Introduction to Programming

Real Number Data Type • Typical representation of a 32-bit float Sign bit

Exponent Bit number

31

Mantissa

22

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0

Real Number Data Type • Typical representation of a 64-bit double Sign bit

Exponent Bit number

63

Mantissa

51

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0

Type Modifier for Real Number Data Types • float <= double <= long double • Typical size and range of real data types for 32-bit CPUs: Data type

Size

Typical range of values

float

32 bits

±3.4e+38 to ±1.1e-38 OR 1.17549e-38 to 3.40282e+38

double

64 bits

±1.7e+308 to ±2.2e-308 OR 2.22507e-308 to 1.79769e+308

long double

80 bits

±1.1e+4932 to ±3.3e-4932 OR 3.3621e-4932 to 1.18973e+4932

Introduction to Programming

Format Indicators • For the printf() function '%' formatter

Appropriate data 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 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-

Introduction to Programming

The 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 character just like any letter or digit Introduction to Programming

The Character Data Type • Some non-printing and hard-to-print characters 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 C program. Introduction to Programming

The Character Data Type Some Non-printing characters Name of Character Alert

Escape Sequence \a

Backslash

\\

Backspace

\b

Carriage return

\r

Double quote

\” Introduction to Programming

Data Types • More on Data Types next time :)

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Variables • Variables are the basic data objects manipulated in a program • All variables must be declared before they are used

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Variable Declaration and Definition • Declaration is used to name an object like a variable • Definition is used to create objects and reserved memory space. • Syntax:

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Variable Declaration • C allows multiple variables of the same type 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; Introduction to Programming

Variable Initialization • A variable may be initialized in its declaration • Example: int height = 10, weight = 20; char choice = ‘Y’, index = ‘a’; • the expression on the right serves as an initializer

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Constants

• Constants are data values that cannot be changed during the execution of a program • A literal is an unnamed constant used to specify data • Example: ‘c’ /* a character literal */ • 5 /* an integer literal */ • 3.1416 /* a float literal */ • “Hello” /* a string literal */ Introduction to Programming

Explicit Constants • An explicit constant is introduced in much the same way as a variable, but with its definition prefixed by the word (or type qualifier) const. • They should be initialized during definition. ... const float pi = 3.14159; ... Introduction to Programming

Preprocessor Constants • Another way to designate a constant is to use the preprocessor command define • Syntax: #define • A #define statement allows you to give names to constants • A #define statement allows you to give names to constants Introduction to Programming

Named Constants No semicolon

• Example: #define PI 3.1416 #define EXCHANGE_RATE 52.50 • The action of #define is just like the search and replace command found in your text editor

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Input/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 on the screen, as in: printf("You made an error - try again!\n"); Introduction to Programming

Input/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

• %c • %s

-

single character. character string.

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+2.)

Input/Output Functions • scanf() – general-purpose output routine • Format: scanf(, addr1, addr2…);

Introduction to Programming

Arithmetic Operators • C supports the arithmetic operators: +

Addition

-

Subtraction

*

Multiplication

/

Division

%

Modulo Introduction to Programming

Arithmetic Operators • Examples: A = 2 + 3; B = 2 – 3; C = 2* 3; D = 4 / 2; E = 5 % 2; Introduction to Programming

Arithmetic Operators • The modulo (%) operator computes the remainder of an integer division • For example, 5 % 2 is 1 because 5 divided by 2 is 2 remainder 1. • Moreover, 11 % 2 is 1 because 11 divided by 2 is 5 remainder 1.

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Arithmetic Operators Floating Point Arithmetic • C requires that in a quotient A/B, the denominator, B, must be nonzero • Division by zero will cause a program crash that is why it should be avoided

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Arithmetic Operators Integer Arithmetic • The quotient of 2 integers is not necessarily an integer. • For example, the quotient 3/4 equals a floating point number 0.75, which is not an integer.

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Arithmetic Operators Integer Arithmetic • If you divide an int by an int, the value you get will be truncated or rounded down to the largest whole number less than the result • For example, • 10/3 = 3 and 3/4 = 0 Introduction to Programming

Unary Plus and Unary Minus • The unary plus (+) operator causes no change to the quantity that follows • where the unary minus (-) operator causes the sign of the following quantity to be changed. • Examples: +5 -5

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Assignment Operator • A statement that assigns a value to a variable is called an assignment statement and has the format: variable = expression • Example: y = 21; Ch = ‘A’; x = (2 + 5) * (10 – 6); net = gross – expenses; Introduction to Programming

Assignment Operator Expression

Equivalent

k = k + 2;

k += 2;

k = k - 2;

k -= 2;

k = k * 2;

k *= 2;

k = k / 2;

k /= 2; Introduction to Programming

Assignment Operator • The semantics is specified by variable op= expression is equivalent to variable = variable op expression • The left side of the equal sign should be a variable, not an expression • Thus, the statement x + 2 = 0; • is not a valid statement Introduction to Programming

Precedence and Associativity • Precedence is used to determine the order in which different operators in a complex expression are evaluated • Associativity is used to determine the order in which operators with the same precedence are evaluated in a complex expression Introduction to Programming

Precedence and Associativity Operators

Associativity

-- ++ - (unary)

Left to right

* /

%

Left to right

+ -

Left to right

= += -= *= /=

Right to left

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Precedence and Associativity • Example: The expression 1 + 2 *3 is equivalent to 1 + (2 * 3) • Expressions inside parentheses are evaluated first • Example: The expression 1 + 2 –3 + 4 –5 is equal to –1 based on the ”left-toright” rule of associativity This expression is equal to (((1 + 2) – 3) + 4) – 5 Introduction to Programming

Precedence and Associativity • The unary operators have higher precedence than the binary plus. And minus • In the expression –a * b – c, the first minus is unary and the second is binary. • Using the rules of precedence, we see that the expression is equivalent to ((-a) * b) – c. Introduction to Programming

Type Conversion • Implicit type conversion happens when 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 integer variable. Introduction to Programming

Type Conversion • We can actually “force” the conversion process to take place • This is called explicit type conversion and is done with a unary operator called a type cast. • Format: (data type) expression Introduction to Programming

Type Conversion • The type cast causes the value of the expression to be converted to the data type. For example, (float) (10 + 2) evaluates to a floating point number, 12.0

Introduction to Programming