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Advanced Higher Computing Based on Heriot-Watt University Scholar Materials

Advanced Higher Computing Based on Heriot-Watt University Scholar Materials. Interface Design. Lesson Objectives. The need for a user interface Types of user interface Command. Early Computer Systems Program Entry.

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Advanced Higher Computing Based on Heriot-Watt University Scholar Materials

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  1. Advanced Higher ComputingBased on Heriot-Watt University Scholar Materials Interface Design Alford Academy Business Education and Computing

  2. Lesson Objectives The need for a user interface Types of user interface Command Alford Academy Business Education and Computing

  3. Early Computer Systems Program Entry Punched tape - program code entered directly into the computer in the form of instructions encoded as patterns of holes on a ticker tape (machine code). Punched card - program code entered directly into the computer as a series of cards on which the program instructions are punched using a special machine (HLL) Alford Academy Business Education and Computing

  4. Punch Card Programming Each line of a program source was encoded on a punch card. A 100 line program would need 100 punch cards plus some CONTROL CARDS at the beginning. 1960s IBM Punch Card Machine A programmer would enter blank 80 column punch cards and use a teletypewriter mechanism to type the lines of the code. The machine would punch a hole in a column to represent the character/symbol Alford Academy Business Education and Computing

  5. JCL JCL Batch Programming 3. JOBS read in batches using a punch card reader 1. Users submit programs to a computer operator as JOBS 2. Operator adds commands to each job telling the computer what the job is – commands written in a JOB CONTROL LANGUAGE 6. Returned to user • Output of programs returned to operator 4. Queue of jobs sent to mainframe for processing Alford Academy Business Education and Computing

  6. Need for a user interface In batch processing there is no interaction between the user and the computer Only highly trained engineers and scientists had direct access to the mainframe operating system A single syntax error in a program eg missing ELSE, misspelt keyword meant that the offending card had to be re-punched and the JOB resubmitted If a program needed to change the logic then the necessary cards would be re-punched and the JOB resubmitted What do you think were the disadvantages of this approach? Any advantages? Alford Academy Business Education and Computing

  7. Influencing factors in the development of human computer interfaces INTERACTIVE SYSTEMS Limitations of batch processing in early mainframe environments Advances in technology – emergence of the desktop computer WHERE HUMANS NEED TO COMMUNICATE DIRECTLY WITH COMPUTERS, THERE HAS TO BE A MECHANISM ie A USER-FRIENDLY INTERFACE THROUGH WHICH THE AVERAGE PERSON CAN INTERACT PRODUCTIVELY WITH A COMPUTER SYSTEM Alford Academy Business Education and Computing

  8. Types of user interface There are different ways in which a user can interact with a computer system:- 1. Command driven 2. Menu driven 3. Graphical User Interface 4. Special purpose The type of user interface and style of interaction is decided at the design stage of the software development process, taking into account the users and the need to support particular tasks. Many systems use a mixture of styles of interaction (command, menu, GUI, etc) Alford Academy Business Education and Computing

  9. Command driven The earliest form of human computer interaction. Using simple teletypewriter technology and simply visual display terminal (VDT), commands entered at a command prompt. A simple serial transmission system used to transmit the commands to the computer. Only needs a basic black and white screen design – usually white text on black background. Alford Academy Business Education and Computing

  10. Command driven - advantages Implemented using cheap, visual display terminals More experienced users have direct control over the operations of the computer Can combine commands into sequences and create more complex commands – macros and command language programs Faster to issue a command sequence directly rather than searching through a menu Alford Academy Business Education and Computing

  11. Command driven - disadvantages Have to learn command languages which can be complex for the average person Mistakes in typing means that the command line interpreter must have error handling and error reporting built in – unlike GUIs and menu driven interfaces where there is little if any typing Operating system commands are seldom the same across different operating systems which means that users must become familiar with different command languages. Alford Academy Business Education and Computing

  12. Activities • Read Scholar pages 27 – 32 and answer Review questions on page 32 • Read Scholar pages 32 – 36 on Menu Driven interfaces, only this time, make up your own mindmap of key concepts (images of menu-driven systems can be found using Google) • Homework – Complete mindmap exercise and print your completed work. Alford Academy Business Education and Computing

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