Back-End = The Brain

Mainy people refer to back-end development code as the brain of the application. It is never visible to the user. It is built with the use of server-side language and databases. This operation is a bit more complex. The developer builds an application which connects with a database to look up, save or change data and return it back to the user in the form of front-end code.

Java

This is my personal favorite language. It is versatile and full-featured. It is everywhere. Java is a general-purpose computer programming language that is concurrent, class-based, object-oriented, and specifically designed to have as few implementation dependencies as possible. It is intended to let application developers "write once, run anywhere" (WORA), meaning that compiled Java code can run on all platforms that support Java without the need for recompilation. Java applications are typically compiled to bytecode that can run on any Java virtual machine (JVM) regardless of computer architecture. As of 2015, Java is one of the most popular programming languages in use, particularly for client-server web applications, with a reported 9 million developers. Java was originally developed by James Gosling at Sun Microsystems (which has since been acquired by Oracle Corporation) and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++, but it has fewer low-level facilities than either of them.


IBM, CL, and RPG

The IBM i Control Language (CL) is a scripting language for the IBM's IBM i platform (previously called OS/400 when running on AS/400 systems) bearing a resemblance to the IBM Job Control Language and consisting of an ever expanding set of command objects (*CMD) used to invoke traditional AS/400 programs and/or get help on what those programs do. CL can also be used to create CL programs (congruent to shell scripts) where there are additional commands that provide program-like functionality (IF/ELSE, variable declaration, file input, etc.)

RPG is a high-level programming language (HLL) for business applications. RPG is an IBM proprietary programming language and its later versions are only available on IBM i or OS/400 based systems. It has a long history, having been developed by IBM in 1959 as the Report Program Generator - a tool to replicate punched card processing on the IBM 1401 then updated to RPG II for the IBM System/3 in the late 1960s, and since evolved into an HLL equivalent to COBOL and PL/I.

OCL

High-level language programs require OCL to be activated. OCL is used to load programs into the system's memory and start them (a process called execution) and assign resources such as disk files, printers, message members, memory, and disk space to those programs. Other abilities, such as displaying text on the screen, pause messages, and so forth, make OCL more powerful.


The Computer
A computer is a general purpose device that can be programmed to carry out a set of arithmetic or logical operations automatically. Since a sequence of operations can be readily changed, the computer can solve more than one kind of problem.