Using variables, declaring constants _ what is a variable_ _ informit
Variables are tools that help the programmer temporarily store data for a finite amount of time. The boxer rebellion tour Constants are tools that help the programmer define artifacts that are not allowed to change or make changes.
Before you actually explore the need and use of variables in a programming language, take a step back and first see what a computer contains and how it works. Gold forecast today Memory and Addressing in Brief
All computers, smart phones, and other programmable devices contain a microprocessor and a certain amount of memory for temporary storage called Random Access Memory (RAM).
Oil futures market In addition, many devices also allow for data to be persisted on a storage device such as the hard disk. Future marketing trends 2015 The microprocessor executes your application, and in doing so it works with the RAM to fetch the application binary code to be executed as well as the data associated with it, which includes that displayed on the screen and that entered by the user.
The RAM itself can be considered to be a storage area akin to a row of lockers in the dorms, each locker having a number—that is, an address. Aud in usd To access a location in memory, say location 578, the processor needs to be asked via an instruction to fetch a value from there or write a value to it. Usd to euro chart Declaring Variables to Access and Use Memory
The following examples will help you understand what variables are. Stock market future predictions 2015 Assume you are writing a program to multiply two numbers supplied by the user. Rmb to usd The user is asked to feed the multiplicand and the multiplier into your program, one after the other, and you need to store each of them so that you can use them later to multiply. Euro usd chart Depending on what you want to be doing with the result of the multiplication, you might even want to store it for later use in your program. Exchange rate aud to usd It would be slow and error-prone if you were to explicitly specify memory addresses (such as 578) to store the numbers, as you would need to worry about inadvertently overwriting existing data at the location or your data being overwritten at a later stage.
When programming in languages like C++, you define variables to store those values. Currency converter zar to usd Defining a variable is quite simple and follows this pattern: VariableType VariableName;
The variable type attribute tells the compiler the nature of data the variable can store, and the compiler reserves the necessary space for it. Usd to ruble exchange rate The name chosen by the programmer is a friendly replacement for the address in the memory where the variable’s value is stored. Dollar to pound chart Unless the initial value is assigned, you cannot be sure of the contents of that memory location, which can be bad for the program. Euro usd rate Therefore, initialization is optional, but it’s often a good programming practice. Silver price chart 5 year Listing 3.1 shows how variables are declared, initialized, and used in a program that multiplies two numbers supplied by the user. Usd to ringgit malaysia LISTING 3.1 Using Variables to Store Numbers and the Result of Their Multiplication 1: #include
This application asks the user to enter two numbers, which the program multiplies and displays the result. British pound exchange rate history To use numbers entered by the user, it needs to store them in the memory. Stock market definitions glossary Variables firstNumber and secondNumber declared in Lines 9 and 13 do the job of temporarily storing integer values entered by the user. Futures and options trading meaning You use std::cin in Lines 10 and 14 to accept input from the user and to store them in the two integer variables. Conversion rate aud to usd The cout statement in Line 21 is used to display the result on the console.
What this line declares is a variable of type int, which indicates an integer, with a name called firstNumber. 1 nzd to usd Zero is assigned to the variable as an initial value.
The compiler does the job of mapping this variable firstNumber to a location in memory and takes care of the associated memory-address bookkeeping for you for all the variables that you declare. Dollar and rupee exchange rate The programmer thus works with human-friendly names, while the compiler manages memory-addressing and creates the instructions for the microprocessor to execute in working with the RAM.
If you declare another set of variables with the same name in main(), then don’t still expect them to carry a value that might have been assigned in MultiplyNumbers().
The compiler treats the variables in main() as independent entities even if they share their names with a variable declared in another function, as the two variables in question are limited by their scope. Secret messages in logos Global Variables
If the variables used in function MultiplyNumbers() in Listing 3.2 were declared outside the scope of the function MultiplyNumber() instead of within it, then they would be usable in both main() and MultiplyNumbers(). Rub usd Listing 3.3 demonstrates global variables, which are the variables with the widest scope in a program. Usd to chf exchange rate LISTING 3.3 Using Global Variables 1: #include
Listing 3.3 displays the result of multiplication in two functions, neither of which has declared the variables firstNumber, secondNumber, and multiplicationResult. Gender articles These variables are global as they have been declared in Lines 5–7, outside the scope of any function. Currency converter usd to aed Note Lines 23 and 36 that use these variables and display their values. Usd to aud rate Pay special attention to how multiplicationResult is first assigned in MultiplyNumbers() yet is effectively reused in main().
Indiscriminate use of global variables is considered poor programming practice. Futures market news This is because global variables can be assigned values in any/every function and can contain an unpredictable state, especially when functions that modify them run in different threads or are programmed by different programmers in a team.
An elegant way of programming Listing 3.3 without using global variables would have the function MultiplyNumbers() return the integer result of the multiplication to main(). Convert to binary code Naming Conventions
In case you haven’t noticed, we named the function MultiplyNumbers() where every word in the function name starts with a capital letter (called Pascal casing), while variables firstNumber, secondNumber, and multiplicationResult were given names where the first word starts with a lowercase letter (called camel casing). Usd to inr forecast 2015 This book follows a convention where variable names follow camel casing, while other artifacts such as function names follow Pascal casing.
You may come across C++ code wherein a variable name is prefixed with characters that explain the type of the variable. Us stock futures cnn money This convention is called the Hungarian notation and is frequently used in the programming of Windows applications. 1 rmb to usd So, firstNumber in Hungarian notation would be iFirstNumber, where the prefix i stands for integer. Today’s exchange rate usd to cad A global integer would be called g_iFirstNumber. Binary to text converter online Hungarian notation has lost popularity in recent years in part due to improvements in Integrated Development Environments (IDEs) that display the type of a variable when required—on mouse hover, for instance.