Introduction to Programming Languages

Programming Languages

• A computer programming language is an artificial language for writing formal instructions that control a computer system's activities
• A program consists of a finite set of sequenced instructions or commands given to a computer for a specific task
• Communication is essential when writing a program for a computer to execute instructions

Types of Programming Languages

• Two main types: low-level and high-level languages
• Low-level languages, also known as machine language, are machine-dependent, fast, and efficient, requiring no translator
• Low-level languages are directly understood by the computer using zeros and ones
• High-level languages do not require knowledge of computer specifics, are machine-independent, portable, and easy to learn and write

Low-Level Language

• Closer to machine language compared to human language
• Examples include machine language and Assembly language
• Machine language is the only language a computer natively understands, executing programs coded in strings of 0s and 1s without a translator
• Advantages include fast and efficient computer use and direct understanding by the computer, and no need for code translation
• Disadvantages include being bulky, time-consuming for writing and reading, prone to errors, difficult to learn, and machine-dependent
• Assembly Language uses mnemonics (symbols) to represent data and instructions, which mitigates issues associated with machine language
• Assembly language requires a translator called an assembler
• Assembler is a special program that translates assembly language to machine language

Assembly Language Advantages and Disadvantages

• Advantages include enabling complex jobs to run simpler, efficient memory use, faster speed, hardware-oriented design, fewer instructions, and suitability for critical jobs
• Disadvantages include machine-dependency, the need for programmer knowledge, cumbersomeness, high development costs, and time consumption

High-Level Language

• A problem-oriented programming language that source programs are written in human-readable languages, like English, instead of symbols
• High-level language is a convenient and simple means of describing the information structures and sequences of actions required to perform a particular task
• Examples of high-level languages include C++, Python, FORTRAN, COBOL, QBASIC, VISUAL BASIC, JAVA, PASCAL, etc

Advantages and Disadvantages of High-Level Language

• Advantages include no need for computer knowledge, program portability, and ease of learning and writing
• Disadvantages include longer translation times to machine code, slower speed compared to low-level programs, less memory efficiency, and inability to communicate directly with hardware

Features of High-Level Language

• Machine independent, problem-oriented, clear structure reflection
• Readability, and program portability

Program Design - Characteristics of a Good Program

• Portability/Transferability is can work on any computer machine
• Reliability is that it can be relied upon to do what it is expected to do
• Efficiency/cost saving means it must not cost more than its benefits while solving problems appropriately, quickly, and efficiently
• Clarity and Simplicity means it should be simple to understand
• Understandability/Readability means it must be readable and understandable by other programmers and end users
• Flexibility/Adaptability/Maintainability means a good program must be flexible, adaptable, and maintainable to suit user needs and easy for modification

Program Design - Phases of Program Development (Programming) Steps

• Problem definition/Analysis
• Selection or development of an algorithm
• Designing the program
• Coding the programming statements
• Compiling/Compilation stage
• Testing/Running and Debugging the program
• Documentation
• Maintenance

Problem Definition/Analysis Stage

• The problem that requires a solution needs to be understood
• Determine the data to be processed, its form/type, volume, and what needs to be done to produce the required output

Selection or Development of an Algorithm

• An algorithm is a set of steps required to solve a problem written down

Designing the Program

• Programmers use flowcharts to minimize software development time
• A flowchart is a pictorial representation of the algorithm developed in the earlier step

Coding the Statement

• Writing the program statements
• Programmers use the program flowchart as a guide for coding the steps a computer will follow

Compiling

• Translating the program's source code to machine or object code if not already in machine language
• A computer program is fed to the computer, and the source program is entered for it to be translated and stored in the memory

Running, Testing, and Debugging

• Activating the computer to run a program, which may encounter syntax, semantics, logic, or runtime errors
• Manuals are used to debug the errors
• Error-free programs are tested using data, and if it works as intended, real life data are then loaded

Documentation

• Documentation is the last stage in software development
• Involves keeping written records that describe the program, explain its purposes, and define the amount, types, and sources of input data to run it
• List the departments and people who use its output and trace the logic the program follows

Maintenance

• Includes all activities after program completion, such as finding/correcting errors, modifying to enhance based on new concepts or hardware/OS changes
• Includes updating documentation, adding features/functions, and removing useless/redundant code

Introduction to Abstraction

• Data abstraction is the reduction of a particular body of data to a simplified representation of the whole
• Abstraction is refining or removing characteristics to reduce it to essential characteristics
• Abstraction hides some system characteristics leaving only the essential ones for simplicity
• Examples include function, method, subroutine, etc

Modularity

• Modular programming is subdividing a program into separate sub-programs
• A module is a separate software component for use in various applications/functions
• Modular programming is essential for thousands/millions of lines which could get syntax errors

Modularity cont.

• The modular programming concept means each sub-module contains a functionality
• Emphasis on breaking large programs into small problems and increases the maintainability, readability, and makes it handy for any changes

Advantages of Using Modular Programming

• Simplicity, as program code is accessed via modules instead of longline code, easing debugging
• Reusability that allows user to reuse functionality with a different interface
• Ease of maintenance that helps collision at the time of working on modules and proper collaboration

Modular Programming in C/C++

• C is a structured programming language as large problems are solved by dividing problems into smaller modules called functions or procedures each handle a particular responsibility
• A program that solves an entire problem consists of a collection of such functions

Modular Programming in C

• Modules are interrelated files that share implementation while hiding it
• Each function defined in C by default is globally accessible
• Achieved by including the header file that has the definition

Modular Programming in C cont.

• Modularization is a way to organize large programs in smaller parts
• Each module has a well-defined interface toward client modules that specifies how services are made available
• Each module hides the code and private details from client modules

Modular Programming Benefits in C

• Benefits include modules being reused in several programs or projects
• Changing modules does not change the clients as far as the interface is unchanged
• Only modified modules are re-compiled faster
• Self-documenting, interfaces are required
• Easier debugging as modules have separated testing

Modular Programming in C cont.

• Splitting every source code into a header file like module1.h to specify how that module talks to clients
• Followed by a corresponding implementation source file module1.c that hides all the code
• The header contains the declarations of constants, types, global variables, and function prototypes that the client programs use and can see
• Everything else stays inside the code file