CS130 Introduction to Programming with VB 6.0 Fall 2001

Computer System Computer hardware Computer software Users + computer professionals

Hardware Computer hardware –Central Processing Unit (CPU): interprets and executes instructions –Main memory (RAM): stores programs/data that are currently being executed/processed; volatile. –Secondary memory (floppy disk, hard disk, CD, DVD): mass backup storage; non-volatile. –Input devices: keyboard, scanners, etc. –Output devices: printers, monitors, etc.

Software Software = program(s); a program is a list of instructions (coded in a particular programming language) that directs the hardware to perform a specific data processing task.

Two types of software Systems software: performs system-oriented tasks such as backing up files; typical system software includes the operating system such as MS Windows and compilers Applications software: performs user- oriented tacks such as wordprocessing; typical applications software includes wordprocessors, Power-point, etc.

Three-levels of Computer Languages Low-level machine language: 0's and 1's Intermediate assembler languages: mnemonics; needs translator known as assembler. High-level procedural languages: needs translators known as compilers; Visual Basic which will be taught in this class is a popular HLL. Natural or spoken language: an ideal; hard to implement due to ambiguities

Visual Basic a brief history BASIC: Beginners All-purpose Symbolic Instruction Code, implemented in the 1960s; easily to learn/use; handles only textual data. Visual BASIC: evolved from BASIC, capable of handling both graphical and textual materials; object-oriented and event- driven language.

Program development life cycle (PDLC)

Flowchart symbols: tools for algorithm development

Structured programming (top-down chart or hierarchy chart or hierarchical input process output or HIPO)

Basic construct (building block) of a program

Example: sales commission computation for female and male salespersons for a company

Object-oriented programming: concepts of class, sub- class, super-class, inheritance, objects (instances)

Unified Modeling Language (UML): describing and documenting an OO system

Event-driven programming paradigm