Introduction to Program and Programming Language

Introduction to Program and Programming Language

If you want to get something done by a person, you will tell him what to do in a language that he understands. 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 the computer understands. Hence, the programming language is a set of rules that provides a way of instructing the computer to perform certain operations.

            A program is a set of instructions written in a specific programming language that a computer can interpret and execute. A computer requires programs to function.

            Programming languages are said to be lower to higher, depending on whether they are closer to the language the computer itself uses (lower, which means 0s and 1s) or to the language that people use (higher, which means more English like). Here, we will consider following groups of languages:

1.      Machine Language / First-generation Language

2.      Assembly Language / Second-generation Language

3.      High-level Language

a.         Procedural and Object-oriented Language / Third-generation Language

b.      Problem-oriented Language / Fourth-generation Language

c.          Natural language /Fifth-generation Language

Machine Language

It is the lowest level of programming language. In this language, information is represented as 0s and 1s. This programming is very tedious and time consuming. A programmer must keep track of a tremendous amount of detail. Programming in machine code has one advantage over programming at other language level – its execution is very fast and efficient because the computer can accept the machine code as it is. Since there is no standard machine language, a program written in machine language for one computer model may not on different model computer.

Assembly Language

In the 1950s, to reduce programming complexity and provide some standardization, assembly languages were developed. Assembly languages, also known as symbolic languages use abbreviations or mnemonic code – codes more easily memorized – to replace the 0s and 1s machine language. For example, ADD and SUB for addition and subtraction operations.

            For an assemble language program to be executed, it must be translated to machine code. This translation is done by translators called assemblers. The program before translation, the assembly language program, is called a source program and the program after translation, the machine language program, is an object program. Assembly language offers several advantages:

·         Standard and easier to use than machine language.

·         Operate very efficiently, although not as efficient as the machine languages.

·         Easier to debug because programs locate and identify syntax errors

However, there are still some disadvantages:

·         Programs are usually very long.

·         Programs are still complex.

·         Assembly languages are still machine-dependent.

High-level Language

High level languages are simple and easy to understand. These languages assist programmers by reducing further the number of computer operation details they had to specify, so that they could concentrate more on the logic needed to solve the problem. There are three different types of high-level languages:

• Procedural and Object-oriented language: These languages are general purpose programming languages. Procedural programming is a type of programming where a structured method of creating programs is used. With procedure-oriented programming, a problem is broken up into parts and each part is then broken up into further parts. All these parts are known as procedures. They are separate but work together when needed. A main program centrally controls them all. Some procedure-oriented languages are COBOL, FORTRAN, and C.

Object-oriented programming is the newest and most powerful paradigms. Object-oriented programming requires the designer to specify the data as well as the operations to be applied on those data as a single unit. The pairing of data and the operations that can be done on it is called an object. A program made using this language is therefore made up of a set of cooperating objects instead of an instructions list. Some examples are C++, Java, and Smalltalk.

These languages have many advantages over machine and assembly languages. These are listed below:

• Program statements resemble English and hence are easier to work with.
• Less time is required to program a problem.
• Programs are easier to understand and modify.
• Programming languages are machine-independent.

However, these languages still have some disadvantages compared to machine and assembly languages:

• Programs execute more slowly.
• These languages use computer resources less efficiently.
• Problem-oriented language: These languages are designed to solve specific problems or develop specific applications by enabling you to describe what you want rather than step-by-step procedures. These languages are categorized into several kinds of application development tools as given below:
• Personal computer applications software like word processors, spreadsheets, database managers etc.
• Query languages and report generators like SQL (Structured Query Language, QBE (Query by Example) etc. to search a database using certain selection commands.
• Decision support systems that help managers to make decisions and financial planning languages.
• Application generators to develop a particular application without writing detail logic.

• Natural language: Natural languages are used in the areas of artificial intelligence and expert systems. These languages are used to make computers more humanlike and allow the computer to become smarter. That is, simulate the learning process by remembering and improving upon earlier information. Two popular natural languages are LISP and PROLOG.

Compilers and Interpreters

For a high level language to work on the computer it must be translated into machine language. There are two kinds of translators – compilers and interpreters. So, high level languages are called compiled and/or interpreted languages.

In a compiled language, a translation program is run to convert the programmer’s entire high-level program, which is called the source code, into a machine language code. This translation process is called compilation. The machine language code is called the object code and can be saved and either run (executed) immediately or later. Some of the most widely used compiled languages are COBOL, C, C++, FORTAN etc.

In an interpreted language, a translation program converts each program statement into machine code just before the program statement is to be executed. Translation and execution occur immediately, one after another, one statement at a time. Unlike compiled languages, no object code is stored and there is no compilation. The most frequently used interpreted language is BASIC.

Some languages are both compiled and interpreted. One popular such language is JAVA.

Program Design

Before writing computer programs we can use different tools to design it. This design helps the programmer to write computer programs more easily, correctly, and quickly. Some most useful program design tools are: algorithm, flowchart, and pseudocode.

Algorithm

An algorithm is a finite sequence of instructions for solving a stated problem. A stated problem is a well-defined task that has to be performed and must be solvable by an algorithm.  The algorithm must eventually terminate, producing the required result. For example, the following algorithm can be used to compute interest given the values of p, n, and r.

1. Enter the values of p, n, and r.
2. Calculate interest i using the formula p × n × r / 100.
3. Display interest i as a result.

Properties of a good algorithm:

• Input: A number of quantities are provided to an algorithm initially before the algorithm begins. These quantities are inputs which are processed by the algorithm.
• Definiteness: The processing rules specified in the algorithm must be unambiguous and lead to a specific action.
• Effectiveness: Each instruction must be sufficiently basic such that it can, in principle, be carried out in a finite time by a person with paper and pencil.
• Finiteness: The total time to carry out all the steps in the algorithm must be finite.
• Output: An algorithm must have output.
• Correctness: Correct set of output must be produced from the set of inputs. For the same input, it must always produce the same output.

Flowchart

A flowchart is a common type of chart that represents an algorithm or a computer program showing the steps as boxes of various kinds, and their order by connecting these with arrows. Flowcharts are used in analyzing, designing, documenting or managing a process or program in various fields. A typical flowchart may have the following kinds of symbols.

• Circles, ovals, or rounded rectangles: Usually containing the word "Start" or "End", or another phrase signaling the start or end of a process.
• Arrows: Shows flow control. An arrow coming from one symbol and ending at another symbol represents that control passes to the symbol the arrow points to.
• Rectangle: Represents processing steps.
• Parallelogram: Represents input and output.
• Diamond: Represents condition or decision. These typically contain a Yes/No question or True/False test. This symbol is unique in that it has two arrows coming out of it, usually from the bottom point and right point, one corresponding to Yes or True, and one corresponding to No or False. The arrows should always be labeled.

For example, the flowchart to calculate simple interest (if balance is greater than or equal to 100000, interest is 5%, otherwise, interest is 3%) is given below:

Pseudocode

It is also called program design language (PDL) or structured English. It is a language and syntax for designing a computer program based on the relative strengths of structured programming and Natural English. At first glance, PDL looks like a modern programming language. The difference between PDL and a real programming language lies in the use of narrative text embedded directly within PDL statements. In pseudocode, we can use language constructs like IF, SWITCH, FOR, WHILE, and DO-WHILE along with Natural English. For example,

GET student’s grade

IF student’s grade is greater than or equal to 50

            PRINT “passed”

ELSE

            PRINT “failed”

ASCII

It is the acronym for the American Standard Code for Information Interchange. ASCII is a code for representing English characters as numbers, with each letter assigned a number from 0 to 127. For example, the ASCII code for uppercase M is 77. Most computers use ASCII codes to represent text, which makes it possible to transfer data from one computer to another.

Text files stored in ASCII format are sometimes called ASCII files. Text editors and word processors are usually capable of storing data in ASCII format, although ASCII format is not always the default storage format.

The standard ASCII character set uses just 7 bits for each character, meaning it can have 128 identifiers, two to the seventh power (2⁷). There are several larger character sets that use 8 bits, which gives them 128 additional characters. The extra characters are used to represent non-English characters, graphics symbols, and mathematical symbols.

Text Editor

A text editor, such as Notepad, is an application program that can be used to create, view, edit, save, and print text files. Text files only contain plain text. These programs provide fewer formatting options than word processors. Text editors can be used to write computer programs or create other documents. Text editors are often provided with operating systems or software development packages.

Software (Information System) Development

Most organizations use a standard set of steps, called a systems development methodology to develop and support their information systems. It is a standard process followed in an organization to conduct all the steps necessary to analyze, design, implement, and maintain information systems. And systems development life cycle (SDLC) is the traditional methodology used to develop, maintain, and replace information systems. It includes different phases as shown in the figure below. This representation of SDLC is sometimes referred to as the waterfall model or classic life cycle.

  

Fig: The systems development life cycle

The first phase is called planning. In this phase, someone identifies the need for a new or enhanced system. These needs are then analyzed, prioritized and arranged into a plan for the information systems department. Here, a potential information systems project is explained and an argument for continuing or not continuing with the project is presented; a detailed plan is also developed for conducting the remaining phases of the SDLC for the proposed system.

The next phase is called analysis. During this phase, the analyst studies the current system and proposes alternative replacement systems. Here, the analyst thoroughly studies the organization’s current procedures and the information systems used to perform organizational tasks. The analyst work with users to determine what the users want from a proposed system. The analyst carefully studies any current systems, manual and computerized, that might be replaced or enhanced as part of this project. The analyst studies the requirements and structures them according to their interrelationships and eliminates any redundancies; generates alternative initial designs to match the requirements; compare these alternatives to determine which best meets the requirements within the cost, labor, and technical levels the organization is willing to commit to the development process. The output of this phase is a description of the recommended alternative solution. Once the recommendation is accepted by owners, you can begin to make plans to acquire any hardware and system software necessary to build or operate the system as proposed.

            The next phase is called design. During this phase, you convert the description of the recommended alternative solution into logical and then physical system specification. Here, you must design all aspects of the system form input and output screens to reports, databases, and computer processes. Logical design is the part of the design process that is independent of any specific hardware or software platform. Theoretically, the system could be implemented on any hardware and systems software. Physical design is the part of the design phase in which the logical specifications of the system form logical design are transformed into technology-specific details from which all programming and system construction can be accomplished.

The next phase is called implementation. In this phase, the information system is coded, tested, installed, and supported in the organization. During coding, programmers write the programs that make up the information system. During testing, programmers and analysts test individual programs and the entire system in order to find and correct errors. During installation, the new system becomes a part of the daily activities of the organization. Implementation activities also include initial user support such as the finalization of documentation, training programs, and ongoing user assistance.

            The final phase of SDLC is called maintenance. In this phase, information system is systematically repaired and improved. When a system is operating in an organization, users sometimes find problems with how it works and often think of better ways to perform its functions. Also the organization’s needs with respect to the system change over time. In maintenance, you make the changes that users ask for and modify the system to reflect changing business conditions.