Module 1 Intro to Program Logic Formulation

[PROGRAM LOGIC FORMULATION] Programming Fundamentals Christian Lester D. Gimeno

Computer Software • Refers to all computer programs or routines which direct and control the computer hardware in the performance of its data processing functions.

Major Categories of Software Applicatio n software System software

Application Software A software that perform a specific task for computer users (e.g., Word processing).

System Software • A software that was designed to help programmers or to control the computer system (e.g. OS; programming tools: translators, debuggers, editors).

System Analysi s The computer age equivalent of the scientific method. In systems analysis, the problem is defined and analyzed and solutions are recommended to management. This process has been formalized and called the Systems Analysis and Design Method.

System Definition A collection of people, machines, & methods organized to accomplish a set of specific functions.

Computer- based IS • A computer-based information system fits all three definitions. It involves people, machines, and methods (procedures & data); it behaves as an integrated whole; and most information systems are composed of a group of subsystems.

Systems Analyst • A person trained in the analysis of complex business system, which typically involve a computer-based information system.

Systems Development Life Cycle • SDLC is used to describe the steps or phases a system goes through from the time it is conceived until it is phased out of existence.

Systems Development Life Cycle Problem identificatio n, opportunitie s, objectives Determinin g informatio n requireme nts Analyzing system needs Designing the recommended system Developing and documenting the software Testing and maintaining the system Implementin g & evaluating the system

Notes on SDLC IDENTIFYING THESE PHASES PROVIDES A FRAMEWORK FOR CONTROLLING, ESTIMATING, AND OBSERVING THE EVOLUTION OF A SYSTEM. EACH PHASE PRODUCES DOCUMENTATION, W/C IS WRITTEN OR PICTORIAL INFORMATION THAT DESCRIBES THE SYSTEM. THIS DOCUMENTATION IN TURN FORMS THE BASIS OF A MANAGEMENT REVIEW THAT DETERMINES WHETHER THE PROJECT SHOULD PROCEED TO THE NEXT PHASE.

Software Development Process • In this process user needs are translated into software requirements; software requirements are transformed into design; the design is implemented in code; and the code is tested, documented, and certified for use.

Notes on Software Development Top-down Software Design The process of designing a program by first identifying its major components, which are called modules; then decomposing them into lower level components. Structured Program Walkthrough A method of program inspection wherein a segment of design or code is presented for questioning; comments about technique, style, possible errors, deviation from standards, & other problems.

Notes on Software Development Alpha Test A program state during the structured code walkthrough. Beta Test The software is not certified or approved for routine use until it has survived this type of test. Beta testing is done by users who accept the pioneer status associated with being first-time users.

Documentation Categories Design documentation Contains data flow diagrams; functional, performance, & data storage requirements; & management reports. Programming documentation Used by technical people to define the architecture of an information system. User documentation Consists of training, operations, & reference manuals that describe how to use the system.

Installation Phase A PHASE IN WHICH A SYSTEM IS INTEGRATED INTO ITS OPERATIONAL ENVIRONMENT AND IS TESTED TO ENSURE THAT IT PERFORMS AS REQUIRED. PUTTING THE SYSTEM INTO USE BY THE PEOPLE WHO MUST RUN AND MAINTAIN IT. PEOPLE MUST BE TRAINED, NEW PROCEDURES INSTITUTED, & THE SYSTEM THOROUGHLY “SHAKEN DOWN” TO ELIMINATE ANY ERROR OR DEFICIENCIES.

Programming Program List of computer instructions required to arrive at the desired results. Algorithm A step-by-step list of instructions for solving a problem. A precisely expressed procedure for obtaining the problem solution.

Programming • Programming Language • A formalize notation that allows algorithms to be presented in a rigorous and precise way. • Types: machine language, assembly language, high-level language, very high- level language (or 4GL)

Programming • Algorithm may be expressed through: • Flowchart • A system of symbols for expressing algorithms; indicates flow of control/sequence of operations. • Pseudocode • A textual representation of an algorithm; close to natural language; becomes part of the program documentation.

Programming Program Flowchart Symbols Commonly-used Pseudolanguage Instructions (Operations)

Pseudolanguage Instructions Format: OPERATION <operand/s> where: OPERATION – pseudocode operation or instruction operand/s – object/s of a pseudocode operation or instruction

Pseudolanguage Instructions OPEN Allows the program that contains the statement to have access to the records of the designated file. READ Used to copy the contents of a record from an external magnetic medium into an input memory area.

Pseudolanguage Instructions WRITE Used to copy the contents of an output memory area to a file stored on an external magnetic medium or a file produced on a printer. CLOSE Terminates a program’s access to the records of a file previously opened.

Pseudolanguage Instructions IF Used to compare the contents of a memory area with those of another memory area or a constant in order to determine whether the condition is true or false. PERFORM Instructs the computer to perform a specified procedure.

Pseudolanguage Instructions MOVE Used to tell the computer that the data contained in one area in memory is to be copied to another area in memory. COMPUTE Used to indicate that a mathematical computation is to take place.

Pseudolanguage Instructions DISPLAY Used to display a literal or the contents of an identifier on the screen. ACCEPT Allows data entered through the keyboard (or any input device) to be stored in a memory area.

Pseudolanguage Instructions DECLARE Used to define the various identifiers to be used in a program. ENTRY Marks the beginning of a procedure. EXIT Marks the end of a procedure.

Problems that can be solved using computers: Computational Problems involving some kind of mathematical processing Logical Involve relational or logical processing Repetitive Involve repeating a set of mathematical and/or logical instructions

Module 1 Intro to Program Logic Formulation

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Module 1 Intro to Program Logic Formulation