computer note

What is a Computer

• An electronic, digital device that stores and processes information.

• A machine that accepts input, processes it according to specified rules, and produces output

• A programmable machine that inputs, processes and outputs data

Computer Consist of

• Hardware

• Software

Hardware• The physical equipment of a computer system,

including the monitor, keyboard, central processing unit, and storage devices.

• Physical equipment used to perform computing tasks (ie, machinery and equipment such as CPU, disks, tapes, modem, cables, etc.); in operation, a computer is both hardware and software.

Software

• A program or set of instructions that controls the operation of a computer. Distinguished from the actual hardware of the computer.

• A series of instructions for the computer that perform a particular task, called a program; the two major categories of software are system software and application software.

Categories of Software

• Application Software

• Operating System Software

Application Software

• Applications software is designed to perform specific tasks.

• There are three main types of application software:– Applications packages– Tailor-made software– General purpose packages

Applications packages

• Examples of applications packages include:

– Word processing software – MS Word, WordPerfect

– Spreadsheet software – MS Excel, Lotus 1-2-3

– Database software – MS Access– Presentation software

Internet and E-Mail Software

• Software used on the internet

Integrated software

• A common type of applications software found on home personal computers is integrated software.

• This is a software package that includes a collection of application software that shares a common set of commands.

Integrated software

Advantages:• Easier to use• Moving data

between programs within the package is easy

• Cheaper than separate programs

Disadvantages:• Tend to have weak

areas (e.g. better at word processing than spreadsheets)

• Data is not easily moved to programs that are not part of the package

• Cheap is not always best!

Tailor-made software

• Tailor-made software is very expensive because it is designed for a specific purpose.

• It is software that is not available ‘off the shelf’ and is usually written or developed for large organisations (e.g. government, banks, insurance companies, manufacturers).

General purpose software

• General purpose software is not specific to a particular user (e.g. MS Word), and may be capable of development into tailor-made software (e.g. MS Access).

• It is very popular because it is usually relatively cheap, well tested, and has wide support (e.g. easy to use manuals and tutorials).

Programming languages

• A program is a set of instructions that the computer can understand.

• Programs are written in programming languages, and there are several different languages that can be used.

• The choice of programming language depends upon who is writing the program and what they want it to do.

Programming languages

• There are two levels of programming language. These are:– Low-level languages (including

machine language/machine code and assembly language)

– High-level languages

Low-level languages

• Low-level languages are easy for the computer to understand but are more difficult for the programmer to write.

Internet and email software

• Are softwares uses on the world wide web.

• Documents can be sent by email.

• The documents are protected by encryption.

• Electronic signatures are sometimes used as part of signatures (digital signatures)

Working of a Digital Signature

• Sender includes a message(signature) that si encrypted.

• Signature is decoded when the message gets to the recipient.

• If makes sense the signature was encrypted properly the message has come from the right source.

Low-level languages

• The lowest-level is machine language or machine code.

• This consists of series of 1s and 0s and is often machine specific (i.e. it will only work on one type of computer).

• All other programming languages have to be translated into machine code in order to work.

Low-level languages

• Assembly language is not as low-level a programming language as machine code.

• It uses simple instructions such as ADD, SUB, and LDA.

• Assembly language needs an assembler to translate it into machine code.

High-level languages

• High-level languages are easier to use because they are designed with the programmer in mind.

• They are not machine-dependent and allow a program to be written so that it can be used on many different computers.

• Many of the instructions in high-level languages are in American English.


• Examples of high-level languages are:

• COBOL – is used mainly for business data processing.

• BASIC – is mainly used as an introductory programming language in schools.



• C++ - is a popular language for developing commercial software.

• LOGO – is mainly used in schools to teach pupils how to write simple control programs.



• JAVA – is particularly suited to writing programs that will search the Internet.

• HTML – Hyper Text Mark up Language is used to develop websites.

Translation languages

• Translation languages convert program commands into machine code.

• There are two main types of translation languages.

• These are:– Interpreters– Compilers


• Interpreters convert each instruction into machine code, and then carry them out.

• Compilers convert the whole program into machine code before carrying the instructions out.


Assembly language

High-level language

High-level language

Assembler Compiler Interpreter

Machine code

Data Handling Software

• Ability of the computer to store,search and find data.

• Ex dbase, Access,Spreadsheet

CAD/CAM

• Computer Aided Design

• Used for designing things like circuit boards and other electronic circuits.

Advantages of using CAD/CAM

• Design can be tested before it is actually produced.

• Image can be viewed in a 3D view.• Accurate design• Portable• The image can be sent to computer-controlled

machine which can make the product automatically from the design.(CAM)

Data Logging

• A system that uses a computer automatically to collect and store data over a period of time.

• Data logging is when the computer records information about its surrounding environment. This could be the temperature, or the amount of light or sound. To do this, you will need to attach data logging equipment to your computer.

QUESTIONS

• An engineer is using a CAD software to produce a new design for a table

• A> State 3 suitable input devices other than a keyboard and a mouse

• B>State 3 features of the CAD s/w that makes it suitable for designing tables

Questions

• What is an assembler?

• What is a systems software

• Explain Software Integration

• State the purpose of a compiler

• State one difference between a compiler and an assembler

Data and Information

• Data : are values stored in the computer by itself they do not make sense.

• Information : is basically processed data

• Ex 50 90 is data but 50 marks and 90 marks are information. Hence when data has been used in some context it is information.

Data collection and preparation

• Analogue data (physical data)

• Digital data

Data Verification

• Verification means checking the input data with the original data to make sure that there have been no transcription errors. The standard way to do this is to input the data twice to the computer system. The computer then checks the two sets of data (which should be the same) and if there is a difference between the two sets of data the computer knows that one of the inputs is wrong

Data Validation

• Validation is a check on DATA INPUT to the system by comparing the data input with a set of rules that the computer has been told the data must follow. If the data does not match up with the rules then there must be an error

File Organisation

• Serial

• Sequential

• Direct Access

Serial File Organisation

• The file is not in any particular order.

• Data reterival becomes difficult.

• Kept when a file is not to be used for a long time

Sequential File Organisation

• Records are in a particular order

• Data reterival is easy.

• Records are often stored either numerically or alphabetically.

Direct Access

• Any record can be found by just looking at the index

• Data reterival is faster.