SOFTWARE DEVELOPMENT LANGUAGES AND ENVIRONMENTS

Transcription

1 HIGHER COMPUTING SOFTWARE DEVELOPMENT SOFTWARE DEVELOPMENT LANGUAGES AND ENVIRONMENTS PROCEDURAL, DECLARATIVE AND EVENT-DRIVEN LANGUAGES 1. A program contains the following statement: is_a(rover,dog). Which type of programming language is being used? Declarative 2. Describe two similarities of procedural and event-driven languages. Uses a range of data types Follow a sequence of control instructions Similar control structures such as selection (if etc) and repetition (loops). Both are modular 3. State two reasons why a programmer would use an event-driven language to develop software. Has specialised routines, with pre-defined code, for event handling. This allows easier creation of a GUI, such as the creation of windows/buttons/data entry etc. Applications with a graphical interface are suited to code being activated by events. Actions attached to clicking of objects will increase interactivity. There is no pre-determined start or end point of code execution (a non-linear program structure). It responds to events dictated by the user. 4. State two features of a declarative language. Consists of facts and rules Which can be searched/queried Uses pattern matching Uses recursion/inheritance 5. A group of students are working together to create a piece of software. Give one reason why a procedural language has been chosen for this task. Procedural has a range of data types control structures such as selection and repetition etc which can be used It is modular /uses of procedures and functions The program can follow a step by step algorithm. 6. Describe what event-driven and declarative language are. Declarative where a knowledge base of facts and rules is set up and can be queried. Event driven where objects react to events, such as clicking a button, and trigger the execution of code. 7. A mail order company requires a piece of software to be developed that will store and process customer details. Event-driven or declarative languages could be used. Give one reason why each type of language may be suitable for the mail order company s purpose

2 Declarative searches can be carried out through queries. Any inputs can be pattern matched against the facts stored without additional coding, as it is built into the language. Event driven could be set up for easy data entry where data operator just clicked on buttons to enter new records 8. How do procedural languages differ from event driven languages? Programs written in procedural languages have definite start and end points. A fixed algorithm determines the order of code execution rather than events dictated by the user. 9. Event driven programming languages differ from declarative languages and more traditional procedural languages in the way programs are executed. Describe how programs are executed in each of these three types of language. Describe a problem in software development where an event driven language would be necessary. Give two reasons to justify your choice. Event driven There is no pre-determined start or end point of code execution. Objects react to events, such as clicking a button, and trigger the execution of code. Declarative is searched based, where searches can be carried out through queries. Any inputs can be pattern matched, against the facts stored without additional coding, to find a solution. Procedural There is a pre-determined start and end point of code execution. Code is executed in sequence on step at a time. Control structures, such as loops, can be easily repeated. Problem - Creating an interactive tutor for children, where selecting different objects causes different parts of the program to be executed. Reasons It is not possible to determine in advance the order in which objects, such as buttons, will be chosen. The programmer will have specialised routines, with pre-defined code, for event handling. This allows easier creation of the Graphical User Interface. He can concentrate on programming each event handler without worrying about how to link them together. 10. NoTow is a company running a city centre car park. The company require software to control the operation of the car park. The software will have modules for actions such as recognising a car is at a barrier, printing an entry ticket and calculating ticket charge. Name the most suitable type of programming language to implement this software. Explain your answer. Event-driven (1 mark) Program is waiting for an event/action from the customer to respond to (1 mark) OR Procedural (1 mark) sequence of instructions with clear start and end point program will be modular, making use of procedures/functions 11. Pupils are using a procedural language to write their programs. State two features of procedural languages. Follows a sequence of instructions/defined start and end point Use of subprograms/functions Range of variable types Program control using repetition and selection structures

3 Uses arithmetical and logical functions 12. State one feature of event-driven languages that is not commonly found in procedural languages. SCRIPTING LANGUAGES AND MACROS Code activated/order of execution assigned to particular user action eg clicking on button Routines/code for handling events Predefined routines for the creation of buttons/windows/forms/etc 1. A bank manager uses a macro once a month to create an alphabetical list of customers whose account balance is over State two benefits of using macros for this type of task. Increased productivity/saves time (since the task will be completed faster than choosing menu choices, dialogue boxes etc.) Customisation of the package by creating your own menu commands/buttons to automate common search/sort Ability to perform complex tasks recorded by another user (with higher skill level) There is less chance of human error 2. A macro can be written in a high level language. State the type of high level language that is used to write macros. A scripting language 3. A macro extends the functionality of a general-purpose package. State two methods of creating a macro. Record a series of keypresses, menu choices and mouse clicks. Using a scripting language. 4. Data can be imported into a spreadsheet to perform additional statistical analysis using a scripting language. (c) (c) Describe two features of a scripting language. Describe two advantages of using a scripting language within the spreadsheet compared to developing all of the code using a high level programming language. Other than importing data suggest another use for a script. High level language embedded within an application or Operating System. Allows you to simplify or customize the features or the user interface of an application. Allows the creation of a macro, which automates frequently used commands initiated by a single keypress, this can lead to increase productivity. Operations to manipulate data at a lower level are available to the programmer. Access to pre-written code of the package such as max, min, sort etc. No need to create a user interface since a familiar one already exists. Creating a report from the data including charts. Combining features of the application package such as complex searching or sorting, or mailmerge. Creating and printing charts based on an analysis.

4 5. A scripting language is a type of high level language. Describe two characteristics of a scripting language not commonly found in a procedural language. High level language embedded within an application or Operating System. Allows you to simplify or customize the features or the user interface of an application. Allows automating of frequently used commands. These commands will be carried out more quickly, this can lead to increased productivity. 6. Describe what is meant by a scripting language. A High Level Language used to write programs (scripts) which are embedded within an application package or control other programs. 7. What is meant by the term macro? A macro is a sequence of instructions recorded as a series of keypresses, menu choices and mouse clicks or written with a scripting language, which has been stored and can be executed by issuing a single instruction. 8. Many applications contain scripting languages. Explain why there is a need for scripting languages within applications. To make an application more flexible/more usable by a larger group of users Allows experts to customise/extend the functionality of the application Allows experts to automate the functionality of the application Allows beginners to perform tasks beyond their level of expertise Creating/editing a macro 9. A sports centre has purchased software to assist with daily tasks such as bookings. The new software includes a scripting language. State one use of a scripting language. Automate complex or frequently used task Writing macros Customising user interface Increase/extend functionality COMPILERS AND INTERPRETERS 1. A manufacturer of palmtop computers with a global positioning system wishes to offer its customers the facility to obtain distances when playing golf. It is helpful for golfers to know the distance from where they are to the hole. This helps the golfer play the next shot. They appoint a software development company to create the software for this new system. The software could be translated using a compiler or an interpreter. State two reasons why a compiler is a more suitable translator for this application. A Palmtop has limited memory and a compiler does not require to be resident in memory once program is compiled. There is a less powerful processor in palmtop and an interpreter would require processing time for further translations. 2. Programmers can use both a compiler and interpreter when constructing the code.

5 Why would an interpreter be used when developing the software? Explain in terms of efficiency the difference between using a compiler compared with an interpreter when translating code related to the pseudocode below. 1. loop 300 times 2. ask user for name 3. store name in array 4. end loop As an interpreter translates line by line, therefore coding errors can be pinpointed and dealt with quickly. The programmer would be able to run partial code (or code with errors in it) and also be able to identify syntax errors as they are typed. Using a compiler the loop would only need to be translated once. The compiler does not need to be in RAM when the code is being executed as the object code (machine code) is created. This frees up RAM & takes up less processing power as code does not need to be translated again when the program is executed. Therefore there will be much quicker program execution. Using an interpreter the loop would need to be translated every time the loop was executed. The interpreter would be resident in RAM during each translation/execution. Every time the code was executed the loop would need to be translated every time (300), thus taking up processor time. Answer must make two clear points - one related to memory usage, the other to processor time. 3. During the production of the payroll system the software developers use both an interpreter and a compiler. Describe when each of these translator programs are used and give a reason for its use. Interpreter - Used during the writing of the software. This may give easier identification of the location of an error, which can then be edited. It also gives the ability to partially test code despite presence of errors in code. Errors can also be more easily traced. Compiler - Used after the software has been completed. This produces object code for a specific processor (a runnable machine code final version). Therefore there is no need for further translations, and the program will execute more quickly. The object code runs without the translator program being present in memory, it is therefore not using storage space in RAM. 4. The latest version of a program is only guaranteed to run on computers using processors from one manufacturer. Describe a solution that will allow computers with other types of processor to use this software product. A programmer could cross compile the original source code, into object code, understood by different processor types.

6 5. Henry works for a company that maintains office buildings. He decides to write a program to print labels for the room keys in a new office block. The block has 38 floors, each with 25 rooms. The label will consist of the floor number and the room number. The design for the program is shown below alongside a sample section of output. For each of 38 floors For each of 25 rooms Display Floor Number: and floor_no Display Room Number: and room_no Next room Display two blank lines Next floor Once the program has been written it must be translated. Describe clearly why using a compiler to translate the code produced from this algorithm would be more efficient in terms of processor usage than using an interpreter to translate the same code. MODULE LIBRARIES Interpreter will translate the contents of the loops every time they are carried out Compiler will translate the contents of the loops once only Saving processor time by reducing the number of translations 1. What is a module library? A set of pre-written, pre-tested program code for use in the development of software. 2. Describe two reasons why a module library would be used during the development of software. Faster software development due to: less design time as the algorithm will be documented. less implementation time as the code is pre-written and can be re-used so there s no need to type the code. less testing time - as code is pre-tested there is no need to go through exhaustive testing. The code should be error free, more reliable and work correctly. Code is already documented. 3. Module libraries are important tools in software development. Describe two items of information you would expect to find about a module in a module library s documentation. Name of the module. Description of the module s function. Parameters required by the parameter. Limitations or known bugs.