C++ Variables -Variables are used to temporarily store data within a program -When you run the program, variables are stored in the computer’s memory -When a value is written in a memory location the value replaces the previous value in that location -When you exit your program, the variables are deleted -We have to first declare a variable before we can use it in C++. Every variable must have a data type and a variable name -In C++ you can declare variables at different places in the program. They have different meanings and scope depending on where they are declared. -For now, we will declare all our variables at the beginning of main() -Examples of variable declaration -int wordCount; (creates an integer variable) -float unitPrice, totalPrice; (creates two float variables) -double result; (creates a double variable) -char grade; (creates a character variable) -const double PI = 3.14156265; (creates a constant that’s value cannot be changed inside the program -Comments start with /* and end with */ or for only one line start with // Naming Rules for Variables -Variable names can range from 1 to 255 characters -Begin all variable names with a letter of the alphabet. After that, variable names can also contain numbers, but no spaces or special characters (except “_”) is allowed -You cannot use C++ reserved words as variable names -Use meaningful names that are easy to read -C++ is case sensitive. All uppercase names usually indicate constants. -camelCase is when you use a lowercase letter at the beginning of the name and uppercase letters for the beginning of other words in the name Integer Types -Numerical integer types are used to represent integers -The basic type is int (the default is signed), which is guaranteed to have a width of at least 16 bits, however on 32/64-bit systems it is almost exclusively guaranteed to have width of at least 32 bits. 8-bit = Up to 256 16-bit = Up to 216 32-bit = Up to 232 64-bit = Up to 264 -Use the command sizeof(datatype) to check the size of data types -Modifiers modify the integer type and can be mixed in any order. Only one of each group can be presented -Signedness -signed- tar (idk she flipped the slide) Examples: Signed Integers = short, int, long, long long Unsigned Integers= unsigned short, unsigned, unsigned long, unsigned long long Floating-point types -Used to represent real numbers such as 3.14 or 0.01, with different levels of precision depending on which type is used -float: single precision type (32-bit) -double: double precision type (64-bit) -long double: precision and range not less than double -In this class, when using fractions just use double all of the time Boolean and character types -Boolean type, known in C++ as bool, can only represent one of two states, true or false -Character types are used to represent a single character such as “a” -The basic type is char, which is a one-byte (8-bit) character Assignment Operator -Assignment Operator assigns what on the right side to a variable on the left -Basically, just assigning values to data types for calculations and stuff -Assignment operator looks for things on the right side of the equation first, so all variables on the right side must have values Strings -The string class is a compound type and it is used to store sequences of characters such as words or sentences -Put #include <string> before the int main -Define it with a name like any other variable
