1. Chapter 3 Arithmetic Expressions, Function Calls, and Output
Programming in C++
Chapter 3
Arithmetic Expressions, Function Calls, and Output

2. What is an Expression in C++?
An expression is any valid combination of operators and operands.
In C++ each expression has a value.

3. Operators can be binary involving 2 operands 2 + 3
unary involving 1 operand - 3
ternary involving 3 operands later

4. Some C++ Operators Precedence Operator Description
Higher ( ) Function call
+ Positive
- Negative
* Multiplication
/ Division
% Modulus (remainder)
+ Addition
- Subtraction
Lower = Assignment

5. Precedence
Higher Precedence determines which operator is applied first in an expression having several operators.

6. Associativity
Left to right Associativity means that in an expression having 2 operators with the same priority, the left operator is applied first.
In C++ the binary operators
* , / , % , + , - are all left associative.
Expression means ( ) - 1
4 - 1 3

7. Evaluate the Expression
7 * % 3 *
means (7 * 10) % 3 *
% 3 *
70 - (5 % 3) * *
( 2 * 4 ) + 9
( ) 71

8. Parentheses Parentheses can be used to change the usual order
Parts in ( ) are evaluated first
Evaluate (7 * (10 - 5) % 3) *
( 7 * 5 % 3 ) *
( 35 % 3 ) *
2 * 17

9. Assignment Operator Syntax
VariableName = Expression
First, Expression on right is evaluated.
Then the resulting value is stored in the memory location of VariableName on left.
NOTE: An automatic type coercion occurs after evaluation but before the value is stored if the types differ for Expression and VariableName

10. What value is stored? float A; float B; A = 8.5; B = 9.37; A = B; 8.5

11. What is stored? float SomeFloat; ?
SomeFloat = 12; // causes implicit type conversion ?
12.0
SomeFloat

12. What is stored? int SomeInt; ?
SomeInt = 4.8; // causes implicit type conversion ? 4
SomeInt

13. Type Casting is Explicit Conversion of Type
int(4.8) has value 4
float(5) has value 5.0
float(7/4) has value 1.0
float(7) / float(4) has value 1.75

14. <iostream.h> is header file
for a library that defines 3 objects
an istream object named cin (keyboard)
an ostream object named cout (screen)
an ostream object named cerr (screen)

15. No I/O is built into C++
Instead, a library provides input stream and output stream
Keyboard
Screen
executing
program
istream
ostream

16. >> is a binary operator
>> is called the input or extraction operator
>> is left associative
EXPRESSION HAS VALUE
cin >> Age cin
STATEMENT
cin >> Age >> Weight ;

17. << is a binary operator
<< is called the output or insertion operator
<< is left associative
EXPRESSION HAS VALUE
cout << Age cout
STATEMENT
cout << “You are “ << Age << “ years old\n” ;

18. Some Expressions int Age; EXAMPLE VALUE Age = 8 8 - Age - 8 5 + 8 13
5 /
6.0 /
float ( 4 / 8 )
float ( 4 ) /
cout << “How old are you?” cout
cin >> Age cin
cout << Age cout

19. What values are stored? float LoCost; float HiCost; LoCost = 12.342;
LoCost = float (int (LoCost * ) ) / 100.0;
HiCost = float (int (HiCost * ) ) / 100.0;

20. Values were rounded to 2 decimal places
LoCost
12.34
12.35
HiCost

21. Functions Every C program must have a function called main ( )
Program execution always begins with function main ( )
Any other functions are subprograms and must be called.

22. What is in a block? {
0 or more statements here }

23. Function Calls
One function calls another by using the name of the called function together with ( ) containing a parameter list
A function call temporarily transfers control from the calling function to the called function

24. Parts of a Function Every function has 2 parts int main (void) heading{
body block
return 0; }

25. What is in a heading? int main (void) type of returned value
name of function
says no parameters
int main (void)

26. More about functions
It is not considered good practice for the body block of main ( ) to be long.
Function calls are used to do tasks
Every C++ function has a return type
If the return type is not void, the function returns a value to the calling block.

27. Where are functions?
located in libraries OR
written by programmers

28. HEADER FILE FUNCTION EXAMPLE VALUE OF CALL
<stdlib.h> abs(i) abs(-6)
fabs(x) fabs(-6.4)
<math.h> pow(x,y) pow(2.0,3.0)
<math.h> sqrt(x) sqrt(100.0)
sqrt(x) sqrt(2.0)
<math.h> log(x) log(2.0)
<iomanip.h> setprecision(n) setprecision(3)

29. Write C++ Expressions for
The square root of b2 - 4ac
sqrt ( b * b * a * c )
The square root of the average of MyAge and YourAge
sqrt ( (MyAge + YourAge) / 2 )

30. Manipulators
Manipulators are used only in input and output statements.
endl, setw, and setprecision are manipulators that can be used to control output format.
endl is use to terminate the current output line, and create blank lines in output.

31. Insertion Operator ( << )
The insertion operator << takes 2 operands.
The left operand is a stream expression, such as cout.
The right operand is an expression of simple type, or a string, or a manipulator.

32. Output Statements SYNTAX (revised)
cout << ExprOrStringOrManipulator
<< ExprOrStringOrManipulator ;

33. setprecision(n)
requires #include <iomanip.h> and appears in an expression using insertion operator (<<)
specifies n as the number of places displayed after the decimal point for floating point values
remains in effect until explicitly changed by another call to setprecision

34. What is exact output? #include <iomanip.h>
#include <iostream.h>
int main ( void) {
float myNumber = ;
cout.setf ( ios::fixed , ios::floatfield ) ; // use decimal format
cout.setf ( ios::showpoint ) ; // print decimal point
cout << “Number is ” << setprecision ( 3 )
<< myNumber << endl ;
return 0 ; }

35. OUTPUT Number is 123.459 value is rounded if necessary to be displayed
with exactly 3 places after the decimal point

36. To Remember
To cause your program to output numbers that have a decimal point to a certain number of decimal places
cout.setf(ios::fixed);
cout.setf(ios::showpoint);
cout.precision(2);
Any output after these statements will have the precision as indicated

37. setw(n)
requires #include <iomanip.h> and appears in an expression using insertion operator (<<)
affects only the very next item displayed
“set width” specifies n as the number of total columns in which to display a number or string (not char data). Parameter n is called the fieldwidth specification. The number of columns used is expanded if n is too narrow.
is useful to align columns of output

38. What is exact output? #include <iomanip.h>
#include <iostream.h>
int main ( void) {
float myNumber = ;
float yourNumber = ;
cout.setf ( ios::fixed , ios::floatfield ) ; // use decimal format
cout.setf ( ios::showpoint ) ; // print decimal point
cout << “Numbers are: ” << setprecision ( 4 ) << endl
<< setw ( 10 ) << myNumber << endl
<< setw ( 10 ) << yourNumber << endl ;
return 0 ; }

39. OUTPUT
Numbers are:
3.1416
each is displayed right-justified and
rounded if necessary and each is
located in a total of 10 columns with
4 places after the decimal point

40. Using setf( )
setf( ) is a function associated with output streams. To call this function use this syntax
DesiredOutputStream.setf( ParameterList ) ;
setf( ) can be used to print the decimal point (even if there are trailing zeros) for floating values that are output, and to specify that the value be printed with a fixed position decimal point (rather than in scientific notation).

41. cout.setf( ) statements
Use the following statements to specify that (for output sent to the cout stream) decimal format (not scientific notation) be used, and that a decimal point be included (even for floating values with 0 as fractional part).
cout.setf( ios :: fixed, ios :: floatfield ) ;
cout.setf( ios :: showpoint ) ;

42. More examples 312.0 4.827 x y float x = 312.0 ; float y = 4.827 ;
cout.setf ( ios::fixed , ios::floatfield ) ;
cout.setf ( ios::showpoint ) ; OUTPUT
cout << setprecision ( 2 )
<< setw ( 10 ) << x << endl ’’’’
<< setw ( 10 ) << y << endl ; ’’’’’’ 4.83
cout << setprecision ( 1 )
<< setw ( 10 ) << x << endl ’’’’’
<< setw ( 10 ) << y << endl ; ’’’’’’’ 4.8
cout << setprecision ( 5 )
<< setw ( 7 ) << x << endl
<< setw ( 7 ) << y << endl ;

43. Program with several functions
main( ) function
Square( ) function
Cube( ) function

44. Value-returning functions
#include <iostream.h>
int Square ( int ) ; // declares these 2 functions
int Cube ( int ) ;
int main ( void ) {
cout << “The square of 27 is “
<< Square (27) << endl ; // function call
cout << “The cube of 27 is “
<< Cube (27) << endl ; // function call
return 0 ; }

45. Rest of Program int Square ( int n ) // header and body here{
return n * n ; }
int Cube ( int n ) // header and body here
return n * n * n ;

46. A void function call stands alone
#include <iostream.h>
void DisplayMessage ( int n ) ; // declares function
int main(void) {
DisplayMessage( 15 ) ; //function call
cout << “Good Bye“ << endl ;
return 0 ; }

47. A void function does NOT return a value
void DisplayMessage ( int n ) // header and body here {
cout << “I have liked math for “
<< n << “ years” << endl ; }