33 Multiple Declarations Variables with the same data type can be grouped

Multiple Declarations • Variables with the same data type can be grouped together and declared in one statement – Format: dataType variableList; – Example: double grade1, grade2, total, average; • Initialization: using a declaration statement to store a value in a variable – Good programming practice is to declare each initialized variable on a line by itself – Example: double grade2 = 93.5; A First Book of C++ 4th Edition 34

Memory Allocation • Each data type has its own storage requirements – Computer must know variable’s data type to allocate storage – Definition statements: declaration statements used for the purpose of allocating storage A First Book of C++ 4th Edition 35

Memory Allocation (cont'd.) A First Book of C++ 4th Edition 36

Common Programming Errors • Forgetting to declare all variables used in a program • Attempting to store one data type in a variable declared for a different type • Using a variable in an expression before the variable is assigned a value • Dividing integer values incorrectly A First Book of C++ 4th Edition 37

Common Programming Errors (cont'd.) • Mixing data types in the same expression without clearly understanding the effect produced – It is best not to mix data types in an expression unless a specific result is desired • Forgetting to separate individual data streams passed to cout with an insertion (“put to”) symbol A First Book of C++ 4th Edition 38

Summary • Four basic types of data recognized by C++ – Integer, floating-point, character, boolean • cout object can be used to display all data types • Every variable in a C++ program must be declared as the type of variable it can store A First Book of C++ 4th Edition 39

Summary (cont'd.) • A simple C++ program containing declaration statements has the format: #include <iostream> using namespace std; int main() { declaration statements; other statements; return 0; } A First Book of C++ 4th Edition 40

Summary (cont'd.) • Declaration statements: inform the compiler of function’s valid variable names • Definition statements: declaration statements that also cause computer to set aside memory locations for a variable • sizeof() operator: determines the amount of storage reserved for a variable A First Book of C++ 4th Edition 41

Chapter Supplement: Bits, Bytes, and Binary Number Representations • This section explains how numbers are stored in a computer’s memory and different means of representing them A First Book of C++ 4th Edition 42

Bits and Bytes • Bit – A switch that can be open or closed • Byte – Group of eight bits • Character code – Collection of patterns used to represent letters, single digits, and other characters • Number codes – Patterns used to store numbers • Words and addresses A First Book of C++ 4th Edition 43