5.1. Programming Concept:

Introduction

If you want to get something done by a person, you tell him what to do in a language that he understand. Similarly, if you want to make the computer to do some task for you, you have to tell the computer what to do in a language that the computer understands machine language, which in the printed form is apt to be an incomprehensible page after page of ones and zeros. How can you then communicate with the computer?

To communicate with the computer is to develop a third language-a language that can be understood by both you and the computer. This is what a programming language is —a set of rules that provides a way of instructing the computer to perform certain operations.

 

5.1.1 Introduction to Programming Language:

A specification of sequence of step by step procedures in a particular programming language to perform certain operation is called program. A program is generally specific in function. Some programs are integrated whereas some are very specific and can solve a particular problem. For example, a program finding the square roots of a given number of a program for solving quadratic equations cannot be used to solve other problems. The program are generally problem dependent. For writing various programs, different computer languages are used, A program is a set of instructions for the computer that tells it what to do. These instructions are written in special programming languages that allow people to communicate With or instruct the machine.

The task of developing programs for the solution of a problem using computer is referred to as computer programming. A programming language is a set, of codes used to write a program, i.e. it is a formal language designed to communicate instruction to a machine (computer). Programming languages can be used to create programs.

Basically, languages can be divided into two categories according to how the computer understands them.

Two Basic Types of Computer Language:

1. Low-Level Languages: A language that corresponds directly to a specific machine. Low-level languages are closer to the hardware

2. High-Level Languages: Any language that is independent of the machine i.e. which are closer to human languages.

 

In this chapter we shall consider the five levels (or generations) of language.

1.    Machine Language / First-generation Languages (1GL)

2.    Assembly Language / Second-generation Languages (2GL)

3.    Procedural Language / Third-generation Languages (3GL)

4.    Problem-oriented Language / Fourth-generation Languages (4GL)

5.    Natural Language / Fifth-generation Languages (5GL)

 

5.1.2 Low Level Language:

Low-level computer languages are either machine codes or are very close them. A computer cannot understand instructions given to it in high-level languages or in English. It can only understand and execute instructions given in the form of machine language i.e. binary. There are two types of low-level languages:

1.    Machine Language: A language that is directly interpreted into the hardware.

2.    Assembly Language: a slightly more user-friendly language that directly corresponds to machine language.

 

1.      Machine language:

Machine language is the lowest and most elementary level of programming language and was the first type of programming language to be developed. Machine language is basically the only language that a computer can understand.

It is almost impossible for humans to use because they consist entirely of number. The lowest level of programming language in which information is represented as strings of Os and 1 s (binary digits or bits) is called machine language. Machine language's instructions typically use some bits to represent operations such as addition, and some represent operands. Every CPU has its own unique machine language.

Machine language instructions typically use some bits to represent operations, such as addition, and some to represent operands, or perhaps the location of the next instruction. Machine language is difficult to read and write, since it does not resemble conventional mathematical notation or human language, and its codes vary from computer to computer. Machine Language is the only language that is directly understood by the computer. It does not need any translator program. We also call it machine code and it is written as string of l's (one) and 0's (zero). When this sequence of codes is fed to the computer, it recognizes the codes and converts it in to electrical signals needed to run it.

For example, a program instruction may look like this:

       1011000111101

It is not an easy language for you to learn because of its difficult to understand. It is efficient for the computer but very inefficient for programmers. It is considered to the first generation language. It is also difficult to debug the program written in this language.

For example: Consider a line from a program segment, which multiplies two numbers.

00010000   01110000        00101011

11110010   01110011        11010010

Clearly, working with this kind of code is not for everybody. Commas, semicolons, and other special character are also represented as combination of 0s and 1s.

 

Advantage Machine Language:

1. The only advantage is that program of machine language run very fast because no translation program is required for the CPU.

2. It is directly understood by the computer.

3. Machine language makes fast and efficient use of the computer.

 

Disadvantages Machine Language:

1.    It is very difficult to program in machine language. The programmer has to know details of hardware tot write program.

2.    The programmer has to remember a lot of codes to write a program which results in program errors.

3.    It is difficult to debug the program.

4.    Programs are not portable to other computers.

s.    It is machine dependent, i.e. program written in machine language for one computer model will not run on a different model computer.

6.    All memory addresses have to be remembered

 

2.      Assembly language

Assembly language is one level above than machine language. It uses short mnemonic codes for instructions and allows the programmer to introduce names for blocks of memory that hold data. One might thus write "add pay, total" instead of "0110101100101000" for an instruction that adds two numbers.

Assembly language is designed to be easily translated into machine language. Although blocks of data may be referred to by name instead of by their machine addresses, assembly language does not provide more sophisticated means of organizing complex information. Like machine language, assembly language requires detailed knowledge of internal computer architecture. It is useful when such details are important, as in programming a computer to interact with input/output devices (printers, scanners, storage devices, and so forth).

The set of symbols and letters forms the Assembly Language and a translator program is required to  translate  the Assembly  Language to machine language. This translator program is called Assembler'.

Example:

The machine code is,

11110010   01110011        11010010        00010000        01110000        00101011

This could be expressed in assembly language statement as, PACK 210(8,13), 02B (4,7)

So, Assembly language does not replace machine language to execute as it must be converted to machine code. It uses meaningful and readable symbols. ADD is used for addition, SUB for subtraction, MUL for multiplication and so on. These are called mnemonics codes. It is considered to be a second-generation language.

 

Advantages Assembly Language:

1. The symbolic programming of the Assembly Language is easier to understand and saves a lot of time and effort of the programmer.

2. It is easier to correct errors and modify program instructions because program locate and identify.

3. Assembly Language has the same efficiency of execution as the machine level language. Because this is one to one translator corresponding machine language between assembly language program and its corresponding machine language program.

4. It is easily modified.

5. They are more standardized and easier to use than machine language.

 

Disadvantages Assembly Language:

1. It is machine dependent language i.e. a program written for one computer might not run in other computers with different hardware configuration.

Programs are not portable to other computers. Assembly language program are very long.

2. Programs are not portable to other computer

3. Assembly language program are very long.

4. Assembly language program are still complex.

5. To execute, it is slow, less efficient than machine language.

 

High Level Languages (HLL):

High level languages assisted programmers by reducing further the number of computer operation details they had to specify, so that they could concentrate more the logic needed to solve the problem.

High-level computer languages use formats that are similar to English. The purpose of developing high-level languages was to enable people to write programs easily, in their own native language environment (English).

High-level languages are basically symbolic languages that use English words and/or mathematical symbols rather than mnemonic codes. Each instruction in the high-level language is translated into many machine language instructions that the computer can understand. Higher level languages are simple languages that use English and mathematical symbols like +, %, / etc. for its program construction. Higher level languages are problem-oriented languages because the instructions are suitable for solving a particular problem. For example COBOL (Common Business Oriented) is mostly suitable for business oriented language where there is very little processing and huge output. There are mathematical oriented languages like FORTRAN (Formula Translation) and BASIC (Beginners All-purpose Symbolic Instruction Code) where very large processing is required.

 

Advantages:

1. High-level languages are user-friendly

2. They are similar to English and use English vocabulary and well-known symbols. They are easier to learn

3. They are easier to maintain

4. They are problem-oriented rather than 'machine'-based

5. A program written in a high-level language can be translated into many machine languages and can run on any computer for which there exists an appropriate translator

6. The language is independent of the machine on which it is used i.e. programs developed in a high-level language can be run on any computer text

 

Disadvantages:

1. A high-level language has to be translated into the machine language by a translator, which takes up time

2. The object code generated by a translator might be inefficient compared to an equivalent assembly language program

 

Types of High-Level Languages:

Many languages have been developed for achieving a variety of different tasks. Some are fairly specialized, and others are quite general.

The three different types of high level languages are:

 

1.      Procedural Oriented Language (3GL):

General-purpose programming languages are called procedural languages or third generation languages. They are languages such as Pascal, BASIC, COBOL, and FORTRAN, which are designed to express the logic, the procedure, of a problem. Because of their flexibility, procedural languages are able to solve a variety of problems.

It is a list or set of instructions telling computer what to do step by step and how to perform the first code to second code, second code to third code and so on. This language makes programmer friendly. These languages are closer to human language. They are easier to read, write, maintain. These programs could run on different machines so they are machine independent, more mathematical and logical expression is used to form statement. English words are used to denote variables, data types, commands, etc. It is also termed as grouping of primary. It is called source code program.

Advantages include:

1.    The program statements resemble English and hence are easier to work with.

2.    Because of their English-like nature, less time is required to program a problem.

3.    Once coded, programs are easier to understand and modify

4. The programming languages are machine-independent.

5. It is written in a step-by-step function, smaller programs written this way are very easy to follow.

 

Disadvantages include:

1. Program executes more slowly.

2. The languages use computer resources less efficiently. They are mostly CUl based language.

3. Procedural coding tends to get very difficult to maintain the larger the code gets. When the lines of code needed start ending up in the thousands it is very difficult for a team of people, or even one person to maintain.

4. Procedural code is difficult to relate with real world objects.

 

2.      Problem Oriented Language/Fourth Generation Language (4GL):

Fourth generation language, also known as problem oriented language, are high level language designed to solve specific problems or develop specific applications such as database, web based application.

Fourth-generation languages may be categorized into several kinds of application development tools:

·         Personal computer application software

·         Query languages and report generators

·         Decision support systems and financial planning languages

·         Application generators

It is used for development of commercial business software. 4GLs are used to access database. For e.g. find all records where name is "smith". It can form thinking and conceptualization. The main families of 4GL are database queries, data manipulation, GUI operators, and mathematical user web development general purpose language.

It is more user-friendly and enhances programming efficiently with usage of English like words and phrases, use of icons, graphical interface, and symbolic representation. Dbase, Sybase, PHP, JavaScript, ASP, JSP, VBScript, Visual.net, VB.Net, ORACLE, etc. are the examples of 4GL

 

Advantages include:

1.    Simplified the programming process.

2.    Use natural languages that impose no rigid grammatical rules

3.    They possess friendly interface.

4. They are easier to use than previously used high level language.

5. It is closely linked to the English language structure.

Disadvantages include:

1. Programs run slower than those of earlier language because their machine Code longer and more complicated to execute.

2. The recent popularity of4GL is closely linked to the development of fast microprocessor.

3. It requires more memory, disk storage so more execution time.

4. Not suitable for solving problem.

 

3.      Natural Language (5GL):

Natural languages are still in development stages, but they promise to have profound effect particularly in the areas of artificial intelligence and expert systems. Natural languages have two characteristics:

·         They are designed to make the connections that humans have with computers more naturals-more humanlike.

·         They are designed to allow the computer to become "smarter"-to actually simulate the learning process by remembering and improving upon earlier information.

A natural language (or ordinary language) is typically used for communication, and may be spoken, signed language (manual communication and body language) to convey meanings, hands, arm, facial expression or written. Natural language processing is the ability of a computer program to understand human speech as it is spoken.

Two popular natural languages are LISP and PROLOG.

 

Advantages include:

1. It answers questions when given a human question.

2. Language processing is focused on developing efficient algorithm to process task.

3. Relieves burden of learning syntax

4. No training!

 

Disadvantages include:

1. It doesn't recognize homonyms. E.g. RAM, Keyboard, Mouse

2. May require more keystrokes

3. May not show context