This document discusses assignment operators and formatted output in C++. It covers using the assignment operator (=) to assign values to variables, shortcut assignment operators like +=, and the prefix and postfix increment operators (++). It also discusses using manipulators like setw, setprecision, and setiosflags to control the formatting of output when using cout. The document provides examples of declaring and initializing variables, accumulating values, and displaying values in decimal, octal, and hexadecimal formats.

1. A First Book of C++A First Book of C++
Chapter 3 (Pt 1)Chapter 3 (Pt 1)
Assignment and Interactive InputAssignment and Interactive Input

2. ∗ In this chapter, you will learn about:
∗ Assignment Operators
∗ Formatted Output
∗ Mathematical Library Functions
∗ Interactive Keyboard Input
∗ Symbolic Constraints
∗ Common Programming Errors
∗ Errors, Testing, and Debugging
A First Book of C++ 4th Edition 2
ObjectivesObjectives

3. ∗ Basic assignment operator
∗ Format: variable = expression;
∗ Computes value of expression on right of = sign, assigns
it to variable on left side of = sign
∗ If not initialized in a declaration statement, a
variable should be assigned a value before used in
any computation
∗ Variables can only store one value at a time
∗ Subsequent assignment statements will overwrite
previously assigned values
A First Book of C++ 4th Edition 3
Assignment OperatorsAssignment Operators

4. ∗ Operand to right of = sign can be:
∗ A constant
∗ A variable
∗ A valid C++ expression
∗ Operand to left of = sign must be a variable
∗ If operand on right side is an expression:
∗ All variables in expression must have a value to get a
valid result from the assignment
A First Book of C++ 4th Edition 4
Assignment Operators (cont'd.)Assignment Operators (cont'd.)

5. ∗ Expression: combination of constants and
variables that can be evaluated
∗ Examples:
∗ sum = 3 + 7;
∗ diff = 15 –6;
∗ product = .05 * 14.6;
∗ tally = count + 1;
∗ newtotal = 18.3 + total;
∗ average = sum / items;
∗ slope = (y2 – y1) / (x2 – x1);
A First Book of C++ 4th Edition 5
Assignment Operators (cont'd.)Assignment Operators (cont'd.)
variable
constant

6. Assignment Operators (cont'd.)Assignment Operators (cont'd.)
A First Book of C++ 4th Edition 6
constant
expression

7. Value on right side of a C++ expression is converted to
data type of variable on the left side
Example:
If temp is an integer variable (int temp), the assignment
temp = 25.89;
causes integer value 25 to be stored in integer variable
temp
A First Book of C++ 4th Edition 7
CoercionCoercion

8. A First Book of C++ 4th Edition 8
CoercionCoercion
Program
Output
Compilation
Warning

9. ∗ sum = sum + 10; is a valid C++ expression
∗ The value of sum + 10 is stored in variable sum
∗ Not a valid algebra equation (in formal
Mathematics)
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Assignment VariationsAssignment Variations

10. Assignment Variations (cont'd.)Assignment Variations (cont'd.)
A First Book of C++ 4th Edition 10
// Initialization value for use in accumulation
// Accumulation

11. A First Book of C++ 4th Edition 11
Assignment Variations (cont'd.)Assignment Variations (cont'd.)

12. Assignment expressions such as:
sum = sum + 25;
can be written by using the following shortcut operators:
+= -= *= /= %=
Example:
sum = sum + 10;
can be written as:
sum += 10; (this means sum = sum + 10)
A First Book of C++ 4th Edition 12
Assignment Variations (cont'd.)Assignment Variations (cont'd.)

13. ∗ The following statements add the numbers 96, 70, 85,
and 60 in calculator fashion:
A First Book of C++ 4th Edition 13
AccumulatingAccumulating

14. Accumulating (cont'd.)Accumulating (cont'd.)
A First Book of C++ 4th Edition 14

15. Has the form:
variable = variable + fixedNumber;
Each time statement is executed, value of variable is
increased by a fixed amount
Increment operators (++), (--)
Unary operator for special case when variable is increased
or decreased by 1
Using the increment operator, the expression:
variable = variable + 1;
can be replaced by
either: ++variable; or variable++;
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CountingCounting

16. ∗ Examples of counting statements:
i= i + 1;
n = n + 1;
count = count + 1;
j = j + 2;
m = m + 2;
kk = kk + 3;
A First Book of C++ 4th Edition 16
Counting (cont'd.)Counting (cont'd.)

17. ∗ Examples of the increment operator:
A First Book of C++ 4th Edition 17
Counting (cont'd.)Counting (cont'd.)

18. Counting (cont'd.)Counting (cont'd.)
A First Book of C++ 4th Edition 18

19. Prefix increment operator: the ++ or -- operator appears
before a variable
̶ The expression k = ++n performs two actions:
n = n + 1; // increment n first
k = n; // assign n’s value to k
Postfix increment operator: the ++ or -- operator appears
after a variable
̶ The expression k = n++ works differently:
k = n; // assign n’s value to k
n = n + 1; // and then increment n
A First Book of C++ 4th Edition 19
Counting (cont'd.)Counting (cont'd.)

20. ∗ A program must present results attractively
∗ Field width manipulators: control format of numbers
displayed by cout
∗ Manipulators included in the output stream
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Formatted OutputFormatted Output

21. Formatted Output (cont'd.)Formatted Output (cont'd.)
A First Book of C++ 4th Edition 21
manipulators

22. A First Book of C++ 4th Edition 22

23. Formatted Output (cont'd.)Formatted Output (cont'd.)
A First Book of C++ 4th Edition 23
//Program 3.5
#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
cout << setw(4) << 6 << endl // set total width of display to 4
<< setw(4) << fixed << setprecision(2) << 18.5 << endl
<< setw(4) << setiosflags(ios::fixed) << 124 << endl
<< “---n”
<< (6+18.5+124) << endl;
return 0;
}

24. ∗ Field justification manipulator
∗ Example: cout << “|” << setw(10) <<
setiosflags(ios::left) << 142 << “|”;
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TheThe setiosflags()setiosflags() ManipulatorManipulator

25. ∗ Field justification manipulator
∗ Example: cout << “|” << setw(10) <<
setiosflags(ios::left) << 142 << “|”;
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TheThe setiosflags()setiosflags() ManipulatorManipulator

26. ∗ oct and hex manipulators are used for conversions
to octal and hexadecimal
∗ Display of integer values in one of three possible
numbering systems (decimal, octal, and hexadecimal)
doesn’t affect how the number is stored in a
computer
∗ All numbers are stored by using the computer’s internal
codes
A First Book of C++ 4th Edition 26
Hexadecimal and Octal I/OHexadecimal and Octal I/O

27. Hexadecimal and Octal I/O (cont'd.)Hexadecimal and Octal I/O (cont'd.)
A First Book of C++ 4th Edition 27

28. A First Book of C++ 4th Edition 28

29. Hexadecimal and Octal I/O (cont'd.)Hexadecimal and Octal I/O (cont'd.)
A First Book of C++ 4th Edition 29