Systems and application software

GOOD DAY, students. This is lesson 15 in our series of lessons. In this week’s lesson, we will continue to look at system and application software. At the end of the lesson, you will be able to distinguish between at least two types of processing modes, compare at least two types of user interfaces, and state the advantages and disadvantages for the three main user interfaces.

The choice of an operating system is also dependent on the processing environment required by the user. The types of processing environment or processing modes are listed below: 1. Batch processing 2. Time-sharing multi-processing 3. Single-user processing system 4. Real-time online processing 5. Single-user multi-tasking processing

BATCH PROCESSING

These are systems that provide multi-programming of batch programmes but have few facilities for interaction or multi-access. Commands or jobs are collected in groups and processed in the order in which they are placed, that is, in a first-in-first-out sequence. Each group of commands or jobs is called a batch. The jobs are entered in a batch queue and then run one or more at a time under the control of the operating system. A job may wait in a batch queue for minutes or hours, depending on the workload. No amendments are possible during processing. Batch processing is often used in utility bill preparation and salary preparation (payroll), which is generally prepared and sent out, for example, at the end of the month to customers or employees, respectively.

TIME-SHARING MULTI-PROCESSING

The processor’s time is divided into small units called time slices and shared, in turn, between users to provide multi-access. These systems allow the CPU to switch between different programmes rapidly so that users are unaware that they were ‘time-sharing’ the CPU with others. Several persons can connect to the main computer via dumb terminals and access different application programmes.

SINGLE USER PROCESSING SYSTEM

These systems came on the scene with the advent of personal computers. The majority of small micro-computer-based systems have operating systems, which allow a user to operate the machine in an interactive conversational mode (response to the user’s message is immediate), but normally, only one user programme can be in main storage and processed at a time. There is no multi-programming of user programmes. Multiprogramming occurs when more than one programme in main storage is being processed, apparently at the same time. This is accomplished by the programmes taking turns at short bursts of processing time.

SINGLE-USER MULTI-TASKING

This system only allows one person to use the computer at a time to do multiple tasks.

REAL-TIME PROCESSING

This is a system that is able to process data so quickly that the results are available to influence the activity currently taking place. There is often a need for multi-processing. Multi-processing is the name for the situation that occurs if two or more processors are present in a computer system and are sharing some or all of the same memory. In such cases, two programmes may be processed at the same instant. These systems are used mainly in critical systems. Critical systems are systems where delay in the processing of data after its input can lead to the destruction of life and property. Examples of critical systems are systems that monitor critically ill patients, nuclear plants, the engine of an aeroplane, etc.

ONLINE TRANSACTION

This is when the data collected is processed and updated immediately. The user can interact directly with the computer at any desired time. The computer responds to the user’s input by outputting some data before the user can do any further input. Daily transactions that involve online processing are as follows: the use of an automated teller machine to make deposits and withdrawals and flight reservations. Also, when bills are paid online, the customer’s account is automatically updated from the withdrawal made to make the bill payments.

USER INTERFACES

The interaction between end-users and the computer is said to take place at the “Human Computer Interface” (HCI) point. The term “Human Computer Interface” is meant to cover all aspects of this interaction, not just the hardware. One of the most important features normally required in an HCI is that it be “user friendly”. As the name suggests, a user-friendly interface is one that the end-user finds helpful, easy to learn and easy to use. It is easy to recognise unfriendly interfaces but not so easy to design one that is certain to be user friendly.

THE MAIN TYPES OF USER INTERFACE

The user interface is made up of a hardware interface and software interface. Hardware interfaces would include the use of touch screens, monitors, and keyboards. Braille keyboards and sensors are non-visual interface components. Additionally, there are three main types of software interfaces: Command driven interfaces Menu driven interfaces Graphical user interface

NOTE

In some situations, two different types of interfaces may be combined, for example, a menu interface with command options.

COMMAND-DRIVEN INTERFACES

One of the long-established methods by which a user can interact with the computer is by the use of commands. Commands enable the user to quickly and simply instruct the computer what to do. However, they require the user to already have knowledge of what commands are available, what they do, and the rules governing how they should be typed, so they are more suited to experienced users than the end-user. A technical person such as a computer operator or programmer would be familiar with the commands or where the end-user continually works with the same programme and, therefore, can gain mastery of the commands.

ADVANTAGES OF COMMAND-DRIVEN INTERFACES

Faster to use once you have learnt the commands For a computer programmer, command-driven interfaces are cheaper to implement.

DISADVANTAGES OF COMMAND-DRIVEN INTERFACES

It is sometimes difficult to remember all the commands, therefore, users have to constantly refer to the software user manual.

The user is restricted to using only the keyboard as the interfacing device, while with other interfaces, a wide variety of input devices can be used.

Commands must be entered at a special location on the screen and in a set format.

MENU-DRIVEN INTERFACES

Menus provide another popular form of user interface. There are many different alternative forms of menus. The simplest menus provide the user with a number of options and a simple means of selecting between them. The user is presented with a choice and, therefore, does not have to remember any commands. The interface is, therefore, suitable for beginners and infrequent users. All the user has to do is to make a choice.

A special type of menu is called a pop-up menu; an additional submenu pops up as a selection is made. You can click anywhere on a given document using the right-click mouse button to allow a pop-up menu to appear.

PULL-DOWN

Pull-down menus are a special type of menu used in windowing and were briefly introduced. It is a menu displayed as a vertical list, which hangs from a horizontal bar on the screen in order to elicit a choice from the user.

ADVANTAGES OF MENU-DRIVEN INTERFACES

The user is presented with a list of options to choose from; he does not need to remember the commands.

Free from typing errors because the user does not have to type the commands.

A wide variety of input devices can be used to interface with a menu.

DISADVANTAGES OF MENU-DRIVEN INTERFACE

Several steps required to issue a command. Once the user has learnt the menu system, it is bothersome to have to wait on the package to present the questions before the commands can be entered.

We have come to the end of this lesson. See you next week when we will conclude looking at user interfaces and the topic system and application software. Remember, if you fail to prepare, you prepare to fail.