Shell (computing)

In computing, a shell is a user interface for access to an operating system's services. In general, operating system shells use either a command-line interface (CLI) or graphical user interface (GUI), depending on a computer's role and particular operation.

The design of a shell is guided by cognitive ergonomics and the goal is to achieve the best workflow possible for the intended tasks; the design can be constricted by the available computing power (for example, of the GPU) or the available amount of graphics memory. The design of a shell is also dictated by the employed computer periphery, such as computer keyboard, pointing device (a mouse with one button, or one with five buttons, or a 3D mouse) or touchscreen, which is the direct human–machine interface.

CLI shells allow some operations to be performed faster in some situations, especially when a proper GUI has not been or cannot be created. However, they require the user to memorize commands and their calling syntax, and also to learn the shell-specific scripting language, for example bash script. CLIs are also easier to be operated via refreshable braille display and provide certain advantages to screen readers.

Operating system

An operating system (OS) is system software that manages computer hardware and software resources and provides common services for computer programs. The operating system is a component of the system software in a computer system. Application programs usually require an operating system to function.

Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources.

For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computer – from cellular phones and video game consoles to web servers and supercomputers.

Examples of popular desktop operating systems include Apple OS X, Linux and its variants, and Microsoft Windows. So-called mobile operating systems include Android and iOS.

FlexOS

FlexOS was a modular real-time multi-user multi-tasking operating system (RTOS) designed for computer-integrated manufacturing, laboratory, retail and financial markets. It was developed by Digital Research's Flexible Automation Business Unit in Monterey, California since 1986 and was marketed since January 1987 as a reengineered derivation of Digital Research's Concurrent DOS 286 multiuser multitasking operating system.

Overview

FlexOS was re-written in C for higher portability across hardware platforms, and it featured very low interrupt latency and fast context switching.

The original protected mode FlexOS 286 version 1.0 was designed for host machines equipped with 286 CPUs, and with adaptations for NEC V60, NEC V70 and Motorola 68000 processors planned. FlexOS 286 executables using the system's native INT DCh (INT 220) application program interface had the filename extension .286. A CP/M API front end (FE) was available as well, using the extension .CMD for executables. (A filename extension of .68K was reserved for FlexOS 68K, presumably derived from Concurrent DOS 68K as of 1986.)

4690 Operating System

4690 Operating System, sometimes shortened to 4690 OS or 4690 is a specially designed Point of Sale operating system, originally sold by IBM; however, in 2012 IBM sold its retail business, including this product, to Toshiba, who now supports it. 4690 is widely used by IBM's retail customers to drive retail systems running their own applications as well as IBM's Application Client Server Environment (ACE), Supermarket Application (SA), General Sales Application (GSA), and Chain Drug Sales Application (CDSA).

It is the follow-on product to IBM 4680 OS, which had been in use by IBM's customers since 1986. The original IBM 4680 OS was based on either Digital Research's Concurrent DOS 286 or FlexOS 286, developed in 1986 as a derivation of Concurrent DOS 286 and introduced in early 1987.

In July 1993 IBM adopted FlexOS version 2.32 as the basis of their IBM 4690 OS Version 1. FlexOS 2.32 supported 286 and 386 modes and had no limit on applications running concurrently.

According to "The Year of the Store?", IHL Consulting Group/RIS News, IBM 4690 OS still had a market share of 12% in the POS register/client market in June 2005, when IBM was starting to phase it out in favour to IBM Retail Environment for SUSE (IRES).