Dec 1998 SE203: Software Engineering (Question 4)

	Each part of this question requires consideration of the various characteristics of programming languages, and of the four generations of programming languages.
(a)	Programming languages possess engineering characteristics, which essentially determine the degree to which the programming language will affect the technical development of the program. List and explain three examples of such engineering characteristics.	[6]
	Any three of the following: 1 mark for correctly identifying the characteristic, 1 mark for a suitable explanation. Ease of design to code translation: indicates how closely a programming language can represent a design representation. Compiler efficiency: Many applications today still require fast, "tight" (i.e. low memory requirements) programs. Languages with optimising compilers may be attractive if software performance is a critical requirement. Source code portability: This generally refers to whether source code may be transported from processor to processor and compiler to compiler with little or no modification. Availability of development tools: These can shorten the time required to generate source code and can improve quality of code. Maintainability of source code: Source code must be easy enough to understand so as to allow modifications according to changes in design.
(b)	(i) Assembly language and machine language are considered to be low-level languages. Describe what is meant by the term low-level language.	[1]
	Low-level languages communicate with the computer hardware (or processor) directly (1 mark).
	(ii) Describe one other similarity between assembly language and machine languages.	[1]
	Similarity: both are machine-dependent (or non-portable) languages (1 mark); or both are generally difficult to use or tedious to code in (1 mark).
	(iii) One difference between assembly language and machine languages is that assembly language is generally easier to use than machine language, and this is because of the use of mnemonics. Explain briefly the meaning of the word mnemonic.	[1]
	Mnemonics are English words (or constructs) used to represent machine opcodes.
	(iv) Identify one application area in which such low-level languages should be used.	[1]
	Application areas: e.g. operating systems (1 mark), device drivers (1 mark). Any type of application or program that communicates directly with hardware should be accepted.
(c)	(i) Second generation and third generation languages are frequently called high-level languages. Give one example of a second generation and one example of third generation language.	[2]
	Example of 2^nd GL. 1 mark for one of : FORTRAN, BASIC, COBOL. 3^rd GL. 1 mark for one of: C, PASCAL.
	(ii) Describe in some detail one advantage offered by high-level languages.	[2]
	High level languages are generally versatile enough for application to a wide range of programs; they are generally also popular, resulting in good establishment (i.e. library routines, documentation) of the language. Other valid alternative answers should be accepted. ! mark for a correct but short answer lacking depth, 2 marks for an illustrative and detailed answer indicating good understanding. No marks should be awarded if candidates simply state easy to use without clarification.
(d)	(i) Write down one example of a 4^th generation language and identify one application area in which the use of 4^th generation languages would be ideal.	[2]
	Example of 4^th GL. 1 mark for one of: Foxpro, Dbase, ACCESS, Paradox etc. Application area. 1 mark for one of: creation of prototype, information-intensive systems, databases. Other correct alternative answers should also be given credit.
	(ii) Explain why 4^th generation languages are considered to be easy to use.	[2]
	Ease of use: in 4^th GL, only the details of what needs to be done must be specified, as opposed to how it is being done; 4^th GL allows for the development or creation of programs in ways that model human means of communication. 1 mark for a correct but short answer lacking depth, 1 mark for a illustrative and detailed answer indicating good understanding.
	(iii) Describe briefly one disadvantage of 4^th generation languages.	[2]
	Disadvantage of 4^th generation language: limited application domain.