7.PROGRAMMING LANGUAGE CONCEPTS

Computer programming language, any of various languages for expressing a set of detailed instructions for a digital computer. Such instructions can be executed directly when they are in the computer manufacturer-specific numerical form known as machine language, after a simple substitution process when expressed in a corresponding assembly language, or after translation from some “higher-level” language

Low level language:

These programming languages are more arcane and difficult to understand . It is designed to operate and handle the entire instruction set of a computer system directly which are generally used to write the system software .e.g. Machine language and assembly language.

Machine Language

Machine language is a collection of binary digits or bits that the computer reads and interprets. Machine language is the only language a computer is capable of understanding.

Assembly Language:

It is a low level programming language which is used as an  interface with computer hardwares. It uses structure commands as substitutions for numbers , allowing humans to read the code easier than looking at binary codes.

Medium Level Language:

It serves as the bridge between raw hardware and programming layer of a computer system . It is designed to improve the translate code before it is executed by the processor . C language is Known as medium level language.

High Level Language (HLL):

A high-level language is a computer programming language that isn’t limited by the computer, designed for a specific job, and is easier to understand. It is more like human language and less like machine language. However, for a computer to understand and run a program created with a high-level language, it must be compiled into machine language.

The first high-level languages were introduced in the 1950s. Today, high-level languages are in widespread use. These include BASIC, C, C++, COBOL, FORTRAN, Java, Pascal, Perl, PHP, Python, Ruby, and Visual Basic.



  • BASIC : Stands for Beginner’s all purpose symbolic instruction code. Normally used by beginners since it is easy to learn.
  • FORTRAN: Stands for formula translation and used in scientific and engineering applications .
  • PASCAL: Named after French Mathematician Blaise pascal and used in scientific applications
  • COBAL: Stands for Common Business Oriented language and used in commercial application
  • C : Very powerful HLL used for variety of purposes including system software.

Language Translator

Computers only understand machine code (binary), this is an issue because programmers prefer to use a variety of high and low-level programming languages instead.

To get around the issue, the high-level and low-level program code (source code) needs to pass through a translator.

A translator will convert the source code into machine code (object code).

There are several types of translator programs, each able to perform different tasks.

Compiler:

Compilers are used to translate a program written in a high-level language into machine code (object code).Once compiled (all in one go), the translated program file can then be directly used by the computer and is independently executable.Compiling may take some time but the translated program can be used again and again without the need for recompilation.

An error report is often produced after the full program has been translated.  Errors in the program code may cause a computer to crash.  These errors can only be fixed by changing the original source code and compiling the program again.

Interpreter:

Interpreter programs are able to read, translate and execute one statement at a time from a high-level language program .The interpreter stops when a line of code is reached that contains an error. Interpreters are often used during the development of a program.  They make debugging easier as each line of code is analysed and checked before execution.




Interpreted programs will launch immediately, but your program may run slower then a complied file . No executable file is produced.  The program is interpreted again from scratch every time you launch it.

Assembler:
Assemblers are used to translate a program written in a low-level assembly language into a machine code (object code) file so it can be used and executed by the computer.Once assembled, the program file can be used again and again without re-assembly.

Algorithms:

It is an effective method that can be expressed within a finite amount of space and time and in a well- defined  formal language for calculating a function.

The desirable features of an algorithm are.

  1. Each step of algorithm should be simple.
  2. It must and in a finite number of steps.
  3. It should be as efficient as possible.
  4. It should be unambiguous in the sense that the logic should be crisp and clear.
  5. It should be effective, i.e. it must lead to a unique solution of the problem.

Flowchart

It is a type of diagram that represents an algorithm work flow or process, Showing the step as boxes of various kinds, and their order by connecting them with arrows.

Flowchat are used in analysing designing, documenting or managing a process or program in various fields . The two most comman types of boxes in a flowchart are

  1. A processing step, usually called activity and denoted as a rectangular box.
  2. A decision , usually denoted as a diamond.



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