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

Basic construct (building block) of a program

Basic construct (building block) of a program

Basic construct (building block) of a program

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