Structured programming language

Structured Programming Language ITSS113 Lecture-1 : INTRODUCTION • To provide brief history of COBOL • To learn the capabilities and limitations of COBOL • To present the program layout of COBOL • To discuss the structure of a COBOL program • To determine the difference between COBOL Literal Set, COBOL Words, COBOL Literals Learning Objectives: Introduction to COBOL • COBOL – Common Business Oriented Language – A third-generation programming language, – Was one of the earliest high-level programming languages; still widely used today. – First proposed in 1959 by the Conference on Data Systems Languages (CODASYL). – Three ANSI standards for COBOL have been produced in 1968, 1974 and 1985. – Object-oriented COBOL is the fourth edition in the continuing evolution of ANSI/ISO standard COBOL. Underlining Philosophy • Like the name suggests, COBOL was meant to be ‘common’ or compatible among a significant group of manufacturers • COBOL is designed for developing business, typically file- oriented, applications, and is not designed for writing systems programs. • Primary domain in business, finance, and administrative systems for companies and governments. Pro’s and Con’s - Disadvantages - very wordy - has a very rigid format - not designed to handle scienc applicaons - Advantages - Simple - Portable - Maintainable Distinct features • The language is simple • No pointers • No user defined types • No user defined functions • ‘Structure like’ data types • File records are also described with great detail, as are lines to be output to a printer • COBOL is self documenting COBOL PROGRAM LAYOUT The layout, or format, or a COBOL program follows certain simple rules, which originated long ago when programs were punched onto 80-column punch cards. COBOL programs are written in coding sheets. There are 80 columns in a line of the coding sheet. COBOL PROGRAM LAYOUT (CONTINUED) Column Field 1-3 Page Number 4-6 Line Number (1-6 Sequence Number) 7 Continuation / Comment 8-11 A – Margin / Area A 12-72 B- Margin /Area B 73-80 Identification Structure of COBOL Program • COBOL programs are hierarchical in structure. – Each element of the hierarchy consists of one or more subordinate elements. • The levels of hierarchy are Divisions, Sections, Paragraphs, Sentences and Statements • There are 4 main divisions and each division provides an essential part of the information required by the complier Structure of COBOL Program (continued) • At the top of the COBOL hierarchy are the four divisions. • The sequence in which they are specified is fixed, and must follow the order: – IDENTIFICATION DIVISION. This division’s primary purpose is to name the program – ENVIRONMENT DIVISION. This division is primarily used to tell the computer about the input and output devices such files or printers. – DATA DIVISION provides descriptions of the data-items/fields processed by the program. – PROCEDURE DIVISION contains the code used to manipulate the data described in the DATA DIVISION. It is here that the programmer describes his algorithm. Note: Some COBOL compilers require that all the divisions be present in a program while others only require the IDENTIFICATION DIVISION and the PROCEDURE DIVISION . to COBOL • COBOL – Common Business Oriented Language – A third-generation programming language, – Was one of the earliest high-level programming languages; still widely used today. – First. Structured Programming Language ITSS113 Lecture-1 : INTRODUCTION • To provide brief history of COBOL • To learn. languages; still widely used today. – First proposed in 1959 by the Conference on Data Systems Languages (CODASYL). – Three ANSI standards for COBOL have been produced in 1968, 1974 and 1985.