Transcript First C++ program, Data Types Powerpoint format

Overview
• Order of presentation different than published
handouts
• Run a program on ccc
• Finish Arithmetic operations
• Data types
integer
char
floating point
• Write a program
Rules of precedence for
Arithmetic Operations
Operator
Operation
Order of evaluation
()
Parentheses
Evaluated first. If the
parentheses are nested the
innermost pair is evaluated
first. If there are several pairs
on the same level they are
evaluated left to right.
*/%
Division, mulitiplication,
modulus
Evaluated second. If there
are several they are
evaluated left to right.
+-
Addtition, subtraction
Evaluated last. If there are
several, they are evaluated
left to right
Example - precedence for
arithmetic operations
algebra: m = a + b + c + d + e
-------------------5
C++: m = (a + b + c + d + e) / 5;
what if parentheses missing? m = a + b + c + d + e
-5
algebra: m = mx + b
C++: m = m * x + b;
Exercises
1) int a, x, b, c, y;
a = 2;
x = 5;
b = 3;
c = 7;
y = a * x * x + b * x + c;
What is y after this program executes?
2) Evaluate the following c++ expressions:
x = 7 + 3 * 6 / 2 - 1;
y = 2 % 2 + 2 * 2 - 2/2;
z = (3 * 9 * (3 + (9 * 3/ (3))));
Integer Data types
• Size and range differ from system to system. Typical:
short (2 bytes) unsigned short 0 to 65535
signed short -32768 to 32765
int (4 bytes)
long (4 bytes)
unsigned int 0 to 4294967295
signed int -2147483648 to 2147483647
unsigned long 0 to 4294967295
signed long -2147483648 to 2147483647
• int is shorthand for signed int
• same operations valid for all
• why so many? conserve memory. Database of all US
citizens, age, social security #.
Determining Size and Range
// Determining the size and range of the the signed long integer type.
#include <iostream>
using namespace std;
int main()
{
cout << "signed long type is " << sizeof (signed long) << "bytes\n";
cout << "largest value of signed long type is " << LONG_MAX << endl;
cout << "smallest value of signed long type is " << LONG_MIN << endl;
return 0;
}
page 45 of book gives other constants. Find out size and range for WPI.
Floating point Data Type
Algebraically: number with fractional part
3.14
3
1.2 x 10
mantissa (1.2) exponent (3)
-2
1.5 x 10
mantissa (1.5) exponent (-2)
Implementation: Varies from system to system. Typical:
sign bit
8 bits exponent
23 bits mantissa
floating point data type
• C++: Use when:
fractions
too big for integer (1 x 10 to the 100th)
• Precision - number of places to right of
decimal point. Limited by size of mantissa
Floating Point Data Types
Type
Typical range
Typical
precision
float
10 e -38 to
10 e 38
10 e -308 to
10 e 308
10 e -4932 to
10 e 4932
6 digits
double
long double
15 digits
19 digits
floating point data type
• implementations differ. Typical
double always >= float
long double always >= double
• Constants
3.14 (double)
3.14L (long double)
3.14f (float)
float f1 = 3.14; //compiler error
Mixing float and integer types
#include <iostream>
using namespace std;
int main()
{
float average;
int numberOfGrades = 2;
int totalOfGrades = 9;
average = totalOfGrades / numberOfGrades;
cout << "The average is " << average << endl;
return 0;
}
mixing float and integer
• could change totalOfGrades to float to fix.
Compiler will promote numberOfGrades
• Could use cast operator to change
totalOfGrades temporarily
average = (float) totalOfGrades/ numberOfGrades;
Things to remember about
floating point data types
• Mantissa is limited in size so value may not
be exact (1/3 = .3333333333...)
• Arithmetic is faster using integer types than
floating point types
• Don’t use equality operators
• Modulus operator not valid for floating
point
• Don’t use floating point #’s for loop control
Exercises
1) create a floating point variable and initialize it to the value 21.654
2) create a floating point variable and initialize it to the value 1.6 times
10 to the 12th power
3) Why would the compiler complain about this statement?
float f = 32.56;
4) Suppose you have a floating point number and you want to separate
the whole part from the fractional part so that you have two integer
values. One contains the whole part and one contains the fractional part
ie. 5.77 -> 5, 77. How would you do it?
Homework
• Use cin to read in a value
double total;
cin >> total;
• To print floating point using cout
cout.setf(ios::fixed, ios::floatfield);
cout.setf(ios::showpoint);
cout << setprecision (2);
char data type
•char ch1;
ch1
one byte
• ASCII set see book 623
A is 65
B is 66
• regularity. A + 1 = B
• initialize with ‘
A < B is true
char ch1 = ‘A’; // stores whole number 65 in
storage cell named ch1
char data type
• routines treat char differently than int
char ch1 = ‘A’;
int int1 = 65;
cout << “ch1 is << ch1 << endl; //displays “ch1 is A”
cout << “int1 is “ << int1 << endl; //displays “ch1 is
65”
• char is shorthand for either unsigned char (0 to
255) or signed char (-127 to 127) varies from
system. What is it on ours?
Data Types Exercises
Given the following declarations, determine the value of the variable
on the left-hand-side of each assignment statement.
int int1, int2, int3;
float f1=1.0f, f2=2.5f, f3=5.0f;
double d1, d2;
char ch1, ch2;
int1 = 5; d2 = 5.0;
ch1 = '5';
int3 = f2;
int2 = int1 / int3;
d1 = f3 - -f1 * 6 / int3 + 8.0 * (int1 - d2);
ch2 = ch1 - 2;
int3 = 'a' - 'A';
ch1 = 'W' + int3;
Operations
• Arithmetic
• Relational (a < b)
• Logical (a && b)
Relational operators
• Used to compare values
• result of relational expression is true or false
a = 1, b = 2
a == b false
a < b true
a > b false
• Used to change execution order of
statements
Relational Operators
Standard
algebraic
expression
C++ operator
Example of C++ Meaning
expression
>
>
a>b
a is greater than
b
<
<
a<b
a is less than b
>=
a >=b
a is greater than
or equal to b
<=
a <= b
a is less than or
equal to b
==
a == b
a is equal to b
!=
a != b
a is not equal to
b
=
Slide relational operators (cont)
• precedence < <= >= > higher than == and !=
a <= b == x > y is the same as
(a <= b) == (x > y)
• arithmetic operators higher precedence than
relational
if x = 2, y = 3
y == 2 * x + 3 evaluated as follows:
2 * x (4)
4 + 3 (7)
3 == 7? (false)
Common programming errors
• Compiler will generate an error if the
operators ==, !=, >=, or <= have whitespace
• Cannot reverse => not same as >=
• using = instead of == common mistake
m== 4 desired.
m = 4 done.
do 4 == m
relational operators exercises
Identify which of the following expressions are true:
Assume a = 0, b = 1, x = 2, y = 3
1) a == b + x
2) b + x == y
3) x - b != y
4) a * b + x * y != x * y
5) a <= b != x <= y
Logical Operators
Operator
Name
Example
True if
!
Not
!x
x is false
&&
And
x && y
x and y are both
true
||
Or
x || y
x or y is true
Logical Operators
• Precedence
!
&&
||
!a && b same as (!a) && b
• Relational operators have higher precedence
than the && and || operators
• a < b && c > d same as (a < b) && (c > d)
Precedence chart
Operator
Type
()
!
*/%
parentheses
not
multiplication, division,
modulus
addition, subtraction
relationals
equality
and
or
+< > <= >=
== !=
&&
||
Precedence Exercises
Exercises
1) Assume a = 1, b = 2, c = 4, d =3 is following expression
true or false?
a < b && c >d
2) Create C++ expression a < b and > c, or x > y and > z