tailieunhanh - MultiBooks - Tổng hợp IT - PC part 158

Tham khảo tài liệu 'multibooks - tổng hợp it - pc part 158', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Question 2. Some High Level Languages HLL 1. COBOL Common Business Oriented Language - COBOL is an exetensively used HLL and since around 1960 several versions have appeared - The original intention was that COBOL should be capable of being compiled and run on any model of computer - COBOL is now employed for many business data processing applications and so a brief explaination of its structure follows - A COBOL program consists of 4 divisions Identifycation division this identifies the prog Enviroment division specifies the computer to be used for compiling and processing Data division specifies the format and relates to these to the names used in the procedure division Procedure division comprises the statements in the source program this is the main part of a COBOL program 2. BASIC Beginners ALL purpose Symbolic Instruction Code - BASIC is a straightforward HLL intended for use in a time-sharing environment in this respect it is particularly beneficial in educational institutions - One of the difficulties with BASIC is the welter of dialects currently in use - Essentially BASIC consists of statements made up of verbs variables. The verbs are similar to those in COBOL but there is a large to them that in effect become the addresses of their locations in the main store - A variable name must be unique and generally consists of one or a few alphabetic characters purhaps followed by a digit 3. PASCAL named after the famous 17th century French mathematician - It was expressly designed as a language to make programming more systematic and discriplired and in these respects lends itself to structured programming - It is however more difficult to learn than are COBOLS BASIC and so is unliked to be accepted as a language for microcomputers are geared to BASIC only Question 3. Operating Systeim - Concept of OS An OS consists of a suite of programs one of which the master kernel or exeactive program remains resident in the main store. This program controls the other OS .