| Atomic | An Atomic operation is an operation that completes which cannot be interrupted. For example, setting a one word integer is an atomic operation while setting the characters in a string can be interrupted because multiple memory operations are needed. |
| Call Stack | A set of data pushed onto the Stack for communications between the calling code and the method called. This data includes a place to store the return value and the parameters passed to the method. Other information may be stored in the call stack based on the operating system and the compiling and linking options used. |
| Class | A class is a user (programmer) defined data type, though there are also classes provided by libraries such as the Java libraries and third party libraries. Classes are sued to create or define an object. A class informs the compiler how much memory is needed to hold the object, what data members are in the object, and what methods are contained in the object. The amount of memory needed for an object is not provided by the programmer. Is is derived by the structure of the class and what it contains. |
| Compiler | A program that reads source code of another program and generates machine code that can run on the computer. In some cases, as with Java, the program is translated in p-code which runs on a virtual machine like the Java JVM. |
| Data Type | A data type is the blueprint for creating and initializing a variable. There are two types of data types: primitive data types and user created data types. The primitive data types allow for the creation of non-object variables such as integers, real numbers, and boolean flags. User created data types are called Classes. Not all user created data types are actually created by the user (programmer). Some of these data types are provided by the Java livbrarys. Some Java data types are string, array. All user created data types create variables that are objects. |
| Declaration | To define a data type such as a class and its properties such as data types and methods. Note, no memory or storage is used by declaring a data type. This information is used by the compiler not the program. You declare a data type like a class. [See Definition] |
| Definition | To create a variable or object. This is when memory is assigned to the object. The object is used by the program. [See Declaration] |
| Element | An element is a term used to refer to something in the program. It can be a class, an object, a variable, a method. Basically any part of a program that is given an identifier, a.k.a. a name or label, is considered an element. |
| Encapsulation | The technique where code and interface are kept separate. The interface defines what is to be done and acts as a public contract to callers. The code is does the actual work to keep the contract to the user or caller. This separation allows the programmers to change how the work is actually implemented without forcing the caller to change its code. |
| Heap | Dynamic memory used when creating dynamic variables, using new in Java. In C++ the Heap is used when one of the allocate methods are called or when using new to create an object. When a dynamically created (new) object is no longer referenced in Java or deleted in C++. The memory used it marked as reusable and may be assigned to the next dynamically created variable. |
| Identifier | An identifier is a name given, by the programmer, to elements in a program. An element can be a class, a variable, a method, etc. The identifier is used to uniquely identify something. |
| Interpreter | A program that reads source code of a scripted language program and executes the script. This involves translating source code into machine code that can actually run on the computer. |
| Interrupt | An event that pauses the current code that is executing so that other code can be executed. There are two major sources of interrupts. The first is an external event occurs that causes the program to pause so that an Interrupt Handler can run. The other is if the program is running on multiple threads, one thread can be paused so that another thread can run. |
| Interrupt Handler | Special code that is used to process external events. This code will interrupt the currently running code. Examples of external events: a button is pushed, a range sensor detects something inside a specified distance. |
| Linker | A program that takes the binary or object file produced by the compiler and assigns addresses to libraries and methods within the program. The output of the Linker is an executable program. |
| Lock | There are several locking mechanisms used in multi-threaded programs. Basically a lock allows a section of code to run to completion in one thread without another thread being able execute the same code or change the same objects. Locks are used to make code thread safe. |
| Multi-Threaded | A program that has more than one thread of execution. Programs that run on multiple threads have to be careful when an object is used on multiple threads at the same time. |
| Package | A package is a collection of classes. Normally, all classes in a package have something in common. The standard for naming packages are to start with a reverse domain, followed by the project name, followed by the subproject name. A project name and the subproject name may be multiple layers separated by “.”. The project name usually is also the path to the source code within a project. |
| Signature | Methods have signatures which are used to resolve which method is being invoked. A method signature is a combination of its return value, its identifier, and its list of parameters. Signatures are important to the compiler when methods using the same identifier exist in the same package and class. |
| Stack | Dynamic memory used when a function is called. When a function is called, the arguments passed to it are pushed onto the Stack and any variables or objects are also pushed onto the Stack. When the function returns, all the variables and arguments are popped off the Stack so that memory is available for reuse. |
| Thread Safe | Code is said to be thread safe if it can be run on multiple threads at the same time without changes to data in one thread being lost to another thread. Thread safety is achieved by using Atomic operations and Locks. |
| UML | Unified Modeling Language – A graphical representation of programming, especially suited of object oriented programming. |