1. Machine Machine language is PL in which program instructions are written in strings of 0s and 1s.The computer circuitry is wired in a manner that it can immediately recognizes the machine language instructions. Machine instruction has two parts. 1st part is operation code (what operation is to be performed) 2 nd part operand (where to find or store the data)

2. Features of Machine Language Machine dependent Difficult programming Requires no language translator Program execution is fast Detailed knowledge is required More error prone Difficult program debugging Low productivity Less hardware resources required

3. Assembly Langyage In assembly program instructions are written by the use of mnemonic codes instead of strings of 0s and 1s

4. Features of Assembly Language It was also machine dependent Easy programming as compared to machine Requires language translator (assembler) Program execution is slow as compared to machine Detailed knowledge is required More error prone Difficult program debugging High productivity as compared to machine More hardware resources are required as compared to machine

5. High Level (3GL) Def: In 3GL the program instructions are written by using English words and familiar mathematical symbols and expressions. The source program of 3Gl is converted into object program by compiler or interpreter Features: machine independent Easy programming as compared to low level langs. High programmer productivity as compared to low level Langs. Easy program debugging and maintenance No detailed knowledge of hardware is required Program execution is slow as compared to low level langs. Better documentation C, BASIC, Pascal, ADA, FORTRAN

6. 4GL Definition: 4GL is the computer programming languages in which commands are closer to everyday speech.4GL include a range of features intended to automate software production.4GL use GUI Icons, objects, help facilities pull down menus and templates for developing software. Features of 4GL: Relatively easy to use and learn Database oriented Include data dictionary Use simple query language Include report generator Code generation is automated Documenting and diagramming tools Include facilities for screen design and dialogue box design

7. 4GL products: Metamail 4GL, INFORMIX-4GL product family (INFORMIX-4GL Rapid Development System, INFORMIX Interactive debugger and INFORMIX-4GL compiler) Types of 4GL: Application Generators (used to develop application programs) Report Generators (used to quickly develop management reports) Graphic Generators ( used to quickly prepare graphics) Decision Support system Tools (used for creating financial schedules, budgets. Retrieval and update languages (used to retrieve information from files or databases and to update the data that they contain Application package