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Transcript of Computer Softwares1
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3.0 Computer software
A computer is a machine that is dumb and unintelligible and it remains so until told to do
otherwise. One way to do this is to communicate with the computer using programming
languages understood by the computer. These programming languages will cause the computer
to perform certain tasks.
3.1 Software
This is a general term that applies to any program (set if instructions) that can be loaded into a
computer from any source. These programs tell the computer what it should do. Generally, there
are two types of softwareoperating system software and application software.
3.1.1 Operating system software
Is a program that initiates and controls the operation of the computer. This software manages
most of the computer activities which could include maintenance of files, resources and running
of application software. Operating system software controls the flow of information through the
computer from the input, processing to the output. It passes control from one program to another
under a system of priority when more than one application program occupies the main storage. It
furnishes a complete record of what took place during processing events. It also provides error
correction routines. That is why it is referred to as resource manager. Also operating system
software can be used to save, name, retrieve and maintain application packages on the
computers. It also help in managing peripherals such as printers, plotters,, keyboards and disk
drives, hence, it is also called a file manager. Examples of operating system software are UNIX,
Microsoft Window 2000, Win 2003, WinXP, MS-DOS etc.
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3.1.2 Application software
Are programs written for general use. They are of two types- user-defined (or specialist)
application software and application package.
1. User-defined application software: are those that are specially designed and tailored tomeet the specific needs of individuals, corporate bodies or establishments. Examples of
these types of software are used by banks for on-line transactions, payroll in agencies and
schools, stock control program and all those used by network service providers in
marketing competitions. E.g MTN, CELTEL, GLO. Such software are usually very
expensive to design.
2. Application packages: these are programs designed for particular types of problems.Since they are for general and unrestricted use, they are mostly cheap and mass-
produced. Application packages falls into the following categories:
Commercial software: these are software that are available and offered for salefor commercial purposes. E.g Microsoft word processor, spreadsheets, computer
graphics
Public-domain software: are software that are available for interested users.They can be duplicated without infringement of copyright. They can be
downloaded via the internet.
Sharewares: are those that are also distributed free of charge, although you couldasked to donate some money for some cause of global concern. e.g wikipedia
Freeware: are groups of software that are also available to interested users free ofcharge. e.g internet explorer, adobe reader
Rentwares: are software that are leased out to user for a token of fee.There are other categories of software that are designed for protective purposes and language
development. These are the utility software and language development software. Utility software
are variety of different programs designed to aid in computer system maintenance. eg. Virus
protection (antivirus), disk back-up, hardware analysis and troubleshooting, memory
management and peripheral supports. On the other hand, language development software are
used by software developers to write programs.
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3.2 Programming languages
Are all the technical activities involved in the production of a program, including analysis of
requirements and all stages of design and implementation. It can also be defined as the coding
and testing of a program.
3.2.1 Classification of programming language
1. Machine language is the only language that can be understood by a computerwithout translation program. This language is written in strings of binary digits 0
and 1. The circuitry of a computer is wired in such a way that it immediately
recognizes the machine language and converts it to electrical signals needed to run
the computer. For example, in the study on how a microprocessor works and control
systems such as dishwasher, cloth washing machines and all that, you will need to to
write programs using the data sheets such as Intel 8085 data book. Example of a
machine code is
1000001111000000011111111111000000000
The code could tell the computer to drain water or turn on the tap.
2. Assembly languageThe next level of programming language is the assembly (or low-level) language,
which consists of a variety of programming languages in which the control and data
structure directly reflects the underlying machine architecture. Such languages
substitutes letters and symbols for strings of binary digits used in machine codes.
They are called symbolic language or pseudo-language the letters are called
mnemonics (a shorthand or help). The programs are called assemblers and are
generally classified as low-level languages. Although assembly language is much
more convenient than machine language, it still requires that the user be familiar with
computer set of instruction mnemonics.
3. High level language
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A large number of high level languages (HLL) have been developed to overcome the
difficulties associated with assembly and machine languages. They are simpler to
learn and use. They make it possible to communicate with a computer using English-
level language and mathematical symbols without the need for detailed knowledge of
the computers internal architecture or instruction set. High-level languages are
known as problem-oriented languages (POL). They include the following:
COBOL: Common Business Oriented Language
BASIC: Beginners All-purpose Symbolic Instruction Codes
ALGOL: ALGOrithmetic Language
FORTRAN: FORmula TRANslation
Others are PASCAL, C++, JAVA etc
All programs written in high-level language must exist in two forms before they are executed by
the computer tom produce the desired results. These states are source and object programs.
3.2.2 Source program
Any program written in HLL or LLL is called a source program. Such a program cannot beexecuted or operated upon by the computer until it has been translated into machine language.
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3.2.3 Object program
Is obtained when a source program is translated using an interpreter, compiler or assembler.
Source programs are translated into object programs internally by the computer.
3.2.4 Translator
Is a program that converts another program written in one language to the equivalent program in
another language. Three types of translators are assemblers, compilers and interpreters.
i. Assemblers: is a program that takes as input a program written in assembly
language and translate it into machine codes
ii Compiler: is a special program which translates the source program of
a high-level language in the object program into machine codes. A
compiler translates the entire program before executing it. Figure 3.1 gives
the process of compilation.
CompilerSource program Object program
Figure 3.1 Process of compilation
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3.2.5 Interpreters
High-level language can also be translated into machine language by programs called
interpreters. An interpreter is a language processor that analyses a line of code and then carries
out specified actions, rather than producing a machine code translation to be executed.
Exercise
Explain the difference between an interpreter and compiler.
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