computer languages

4.1.2 Assembly language and Assembler:  

            A low level first generation computer language, popular during early 1960s, which uses abbreviations or mnemonic codes ( mnemonic means mind full) for operation codes and symbolic addresses. This symbolic instruction language is called Assembly language. One of the first step in improving the program preparation was to substitute mnemonics for operation codes. The mnemonics are different  among makes and models of computer. Second step was symbolic addressing to express an address in terms of symbols convenient to the programmer. Another improvement was the programmer turned the work of assigning and keeping track of instruction addresses over to the computer. The programmer merely told the machine the storage address number of the first program instruction and the assembly language software the automatically stored all others in the sequence from that point.

The mnemonics are converted into binaries with the help of a translator known as Assembler.

Assembler

Assembly language

Machine language

The program written using mnemonics is called Source program or assembly language program , the binary form of the source program equivalent is called Object Program.

                        Let us consider an assembly language program

                                       LDA 9000

                                       MOV B,A

                                       MOV C,A

                                       HLT

  Assembler  is used to convert assembly language into the machine language.

  For example object program or machine language equivalent for the above assembly language is

   01110 0100001100

   01110011101

    0111110000

    1011100000

            Assembly language programs are commonly used to write programs for electronic controls using microprocessors e.g., compilers , operating systems, animation in computer graphics and so on.

Assembly language is relatively easy for the human beings compared to machine language. Programs writing are faster compared to machine language. 

Assembly language programmer should know details of the architecture of the machine. Assembly language programs are not portable.

4.1.3 Higher level languages and compiler:

Instructions which are written using English language with symbols and digits are called high level languages. The high level language is closer to our natural language.  The commonly used high level languages are FORTRAN, BASIC, COBOL, PASCAL, PROLOG, C, C++ etc. The complete instruction set written in one of these languages is called a high level language program or computer program or source program.

In order to execute the instructions, the source program is translated into binary form by a compiler or interpreter. A compiler is also used to translate source program into an object program. An interpreter is a program which takes the source program line by line and converts into machine code line by line. .

C language uses a compiler as its translator to translate or compile the complete C program. It is also necessary to create an executable program to execute the instructions given in a source program by linking the input and output devices with your program. A linker (another program) is used to link library routing and generate an executable program from an object program.  Compiler converts source program into object program in terms of stages called passes. Normally, most of the compilers uses two passes to convert source program into the machine language program.

Gwbasic is an interpreter used to convert basic program into object program.

4.2 Compiler:

            Compilers convert the program instructions from human understandable form to the machine understandable form and the translated program instruction is called object code. Compiler is nothing but a language translator used to translate the entire program of the high level language into machine language. Every programming language requires its own compiler to translate the program. For example, the programming language PASCAL  requires PASCAL  compiler and C uses C compiler.

Compiler

High level  language

Machine language

4.3 Interpreter:

            Interpreters also convert the source program to machine language instruction  but executes each line as it is entered. The translation of the source program takes place for every run and is slower than the compiled code. An interpreter must accompany the object code to run a program. Programming languages BASIC and LISP use interpreters.

Interpreter

High level  language

Machine language

4.4 Editor:

            An editor is used to type the source program and store program in disk. C language uses one popular Boroland’s a IDE (Integrated Development Environment) editor in MS-DOS system and in Vi editor in UNIX system. In dos, we use popular Edit editor also.

            Editors  are commonly used to type and edit documents and store them. Thus, they are also called text editors. In word processors  we can perform the operation like setting up margins, spell check and so on. MS-WORD is one of the popular word processor.

Types of Software

Two type of software Like System Software And Application software

4.5 System software:

            System software is designed for a specific type of hardware. For example, the disk operating system (DOS) is used to co-ordinate the peripherals of a computer. The system software controls the activities of a computer, application programs, flow of data  in and out of memory and disk storage. Our operating system, compilers, assemblers, linker and loaders are the example of system software.

System software also handles data in communication applications and within the computer systems in a computer network. The communication software transfers data from one computer to another. These programs also provide data security and error checking along with the transfer of data between the computer systems.

4.6 Application software:

            Application software are developed for application of the computer to common problems and tasks. They are available for business applications, science and engineering applications and so on. Personal productivity programs are categorized based on the nature of their use in word processing, generating spreadsheet, presenting graphics and maintaining databases. Application software is also available as packages and usually with a user manual.

Some of the application software are:

a)      Word processors:

                  A word processor is used to prepare a report, a personal or business letter, in desktop publishing and so on. These offer formatting features such as using different character styles, line spacing, and page numbering and so on. Documents prepared using a word processor can be easily printed in any type of printer.

b)     Electronic spread sheets:

An electronic spreadsheet software is used to prepare documents containing information or data in the form of numbers or characters. The information is arranged in rows and columns for further processing and analysis, preparing reports and generating charts. It is also capable of performing arithmetic operations and using functions.

c)      Database software :

Databases are records related to a person or an organization. Database software have capability to edit and update data in a file. The data are processed to prepare and print salary details of employees, annual sales details and so on. One of the major applications of a computer is database management.