Intro. 4002-208 to Prog. [in C++]
Day 03 Assignment Statement & Data Types
Objectives
Numeric data types Assignment Statement Type conversions
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Data Types
Integer (counting)
char 1 byte short 2 bytes int 4 bytes -128 to +127 -32,768 to +32,767 +/- 2 x 109
Examples
int age; int age, numEmp; int age = 0; //declare age with initial value of 0
Most commonly used types are in bold.
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Double Data Types
Floating Point (calculator numbers)
float 4 bytes double 8 bytes 7 digits and 10+/-38 15 digits and 10+/-308
Examples
double weight = 3.4; double side1 = 0.0, side2 = 1.0, side3 = 2.3;
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Numeric Literal
A number such as 7 or 3.14159 used in an arithmetic expression. The literal must be stored in memory How is the data type determined? If a decimal point is present, then double otherwise int. int: 7 +7 -7 double: -7.2 7. 7.0 6.023e-23
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Assignment Statement - Basics
variable = expression; The symbol = is not algebraic equality. First, the value of the expression is calculated. Second, the value of the expression is assigned to the variable on the left of the assignment sign.
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Arithmetic Operators
Standard operators:
+ (addition) - (subtraction) * (multiplication) / (division)
Valid for integer and floating point types
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Modulus Operator for Integers
If both operands are integers, the result of the operation is always an integer. The result of the division operator is the quotient. The result of the modulus (%) operator is the remainder. 74 / 12 has a result of 6 (quotient only) 74 % 12 has a result of 2 (remainder only)
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Examples
double dv1 = 2.4; double dv2 = 2.0; double dv3 = 3.5; double dv4, dv5, dv6, dv7; dv4 = dv1 + dv2 + dv3; dv5 = dv1 + dv2 dv3; dv6 = dv1 * dv2 dv3; dv7 = dv1 / dv2 * dv3;
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Rules
Precedence (order of evaluation)
Unary +, unary - (highest) */ +(lowest)
Operators of same precedence are done left to right. An expression inside parenthesis ( ) is done first.
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More Examples
double dv1 = 2.4; double dv2 = 2.0; double dv3 = 3.5; double dv8, dv9, dv10, dv11; dv8 = dv1 * dv2 + dv3; dv9 = dv1 * ( dv2 + dv3); dv10 = dv1 / dv2 dv3; dv11 = dv1 / (dv2 - dv3);
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Number Representation
Floating point numbers are represented using IEEE 754 standard Similar to scientific notation d.dddd x 10exp except in binary.
steve.hollasch.net/cgindex/coding/ieeefloat.html
Integer numbers are by represented a method known as 2s complement
www.cs.cornell.edu/~tomf/notes/cps104/twoscomp.html
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Mixed mode operation
If the types of the two numeric operands are different, the value of the smaller type is converted to the larger type. Order:
short (smallest) int long float double (largest)
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Promotion
The data in the smaller type is promoted to a larger type. No data is lost. Other examples float to double short to int int to double
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Examples
double dv1 = 2.4; double dv2 = 2.0; int iv1 = 4; int iv2 = 6; double dv12, dv13, dv14; dv12 = dv1 + iv1; dv13 = dv2 + iv1 * iv2; dv14 = dv2 / (iv1 / iv2);
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Multiple Assignments
The value of the expression may be assigned to several variables. length = width = side + 2.0; The value of side + 2.0 is calculated. This value is stored into width. The value stored in width is then stored into length. More on this careful wording later.
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Multiple Assignments
The value of the expression may be assigned to several variables. length = width = side + 2.0; The value of side + 2.0 is calculated. This value is stored into width. The value stored in width is then stored into length. More on this careful wording later.
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Type Conversion
When the type of the expression does not match the type of the variable. Examples:
double dblVar; int intVar; dblVar = 7; //integer 7 assigned to double intVar = 7.3; //double 7.3 assigned to integer
What happens?
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Conversion (cont.)
The value of the expression on the right must be converted to the type of the variable on the left of the =. dblVar = 7; //the integer 7 is converted to a double 7.0 - Promotion intVar = 7.3; //double value 7.3 is truncated to an integer 7 - Demotion
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Types of Conversions
Implicit
The conversion happens automatically. Maybe be unexpected. Loss of accuracy as the larger value is truncated so that it can be stored in smaller location. Warning issued by most compilers.
Explicit
Conversion indicated by programmer.
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Explicit Type Conversion
When programmer uses a type cast to convert one data type to another. Example: int n; n = static_cast <int> (3.99); //C++ style - orn = (int) 3.99; //C style
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Operator Precedence
Highest to lowest precedence () function calls - ,+ unary operators (- called negation) *,/,% + , - (binary operators) Evaluate expression inside ( ) first.
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