Programming

Overview

• The difference between different types of languages from assembler, through high level languages to 4GLs and object-oriented languages. An outline history of the development of languages over the years
• Differences between procedural and declarative languages
• Summary of the stages of the translation process – compiler and interpreter
• An appreciation of assembly language code through a limited set of operation codes. How these build into a program. Writing full programs is not required

Program Development

• Overview of the stages of program development from receiving a program specification to handing over a fully tested and documented program applied to a professional programmer. Candidates should have an appreciation of the difference of scale of real programs compared with classroom exercises
• Initial understanding of the problem. Checking details with the systems analyst
• Create algorithms for real problems
• Comparison of different algorithmic methods – flowcharts, pseudo-code, decision tables, Jackson charts. Advantages and disadvantages of each
• Define structured programming and construct. The three main constructs – sequence, selection, iteration. Top down programming
• Modular programming. How modular program can be implemented. Advantages and disadvantages of their use
• Prototyping. Advantages and disadvantages of its use

Input and Output of data

• Data types and the operations that can be performed with each
• Keyboard entry of data. Handling and correcting invalid data
• Standard output layouts. Invoices. Account ledgers
• Design a layout for a given situation. This must be workable in the real world
• Differences between output on a screen and a printer

Filing data

• The need for files. The consequences of filing systems not being available
• File structure. Organisation and access methods. An appreciation that a file might be accessed for more than one purpose and so determining the method of organisation
• Programming for serial and sequential files. Commands relating to file handling – open, close, read, write, check end of file, append
• Programming to locate records from the whole file that satisfy a given condition
• Programming to accumulate values from each record in a file
• Programming to merge two similar files into one
• Sequential master file update from an unsorted transaction file. Candidates will not be expected to program for this

Handling data in memory

• Variables – rules for naming variables/procedures/functions
• Performing calculations
• Decisions – IF, CASE

Loops. Difference between the three main looping features and when to use them

• FOR/ENDFOR for fixed number of repeats
• REPEAT/UNTIL for variable repeats – the process is always executed at least once – test for exit at the end
• WHILE/ENDWHILE for variable repeats – the process may not execute even the first time in rare situations – test for exit at the beginning. Use of data TERMINATORS

Arrays – 1-dimensional and 2-dimensional

• Read all data into an array
• Output all data from an array
• Search an array for a given value
• Accumulate values held in some elements of an array
• Use one array to find data to access another

Text data – extract character(s) from a string. Joining strings

Procedures/Sub routines and Functions

• Use of procedures for structuring and re-use processes. Library of procedures/functions
• Parameter passing. Calling a procedure. How parameters are handled internally
• Difference between procedures and functions
• Standard functions such as:(a.) Numeric – SQRT, ABS, INT, RANDOM, SIN/COS/TAN. (b) String – LEFT, RIGHT, ASC, VALUE. {The names may vary in different languages}.

Testing

• Plan the structure of test data for a program
• Design test data for valid and invalid situations
• Perform a dry run/desk check using test data and an algorithm – lay out the results in table format showing the value of variables only as they change
• Programming to test invalid conditions and subsequent repeated re-entry after data is rejected until it is finally accepted
• Testing by program. Recording the results in a test log. Levels of testing – module, program, system, user acceptance
• Methods of locating errors of logic – dry run, trace routines, test bed routines, temporary print commands inserted
• Difference between syntax and logic errors. How and when syntax and logic errors are detected and corrected

Documentation

• The need for documentation
• Documentation for the maintenance programmer
• Documentation for the user
• The reasons why user and maintenance programmer documentations are different
• Uses and benefits of comments/annotations in program listings