Lesson Note On Programming Languages

Programming Languages

Two types of computer languages are used for programming, namely Low Level Languages and High Level Languages. Low Level Languages are further classified as Machine Languages and Assembly Language. High Level Languages are Fortran, Cobol, C, C++, Pascal, Java, etc

Low Level Languages:

Machine Language:

The lowest form of computer language is Machine Language.  Computer CPU can understand only instructions, written using pattern of 0s and 1s i.e. binary language. Hence, in machine language, instructions are formed with different combinations of the bits 0 and 1. For example, 001010110011 could represent an instruction in machine language. The instruction is followed by the data, if needed, in binary form. CPU of every computer (Microprocessor) is capable of executing a particular set of instruction in binary form. This set contains instructions for arithmetic operations, control, input and output operations. The programs written in machine language are called Object Programs. Coding the program in binary form is very tedious. Moreover, the bit patterns for every instruction in a set of about millions of such patterns are difficult to remember. Therefore, a symbiotic language called as Assembly Language was developed.

Assembly Language:

Assembly language consists of symbiotic words called mnemonics and it was extensively used during 1950. Symbolic instruction codes like ADD, SUB, MULT, DIV, IN, OUT etc. are used for operations of addition, subtraction, multiplication, division, input, and output respectively on the data. A set of such instruction codes were put together to form a program and store in memory, means were provided to translate these codes in to their machine language counter parts. The translated program is then directly executed. The assembly language instruction set is different for different microprocessors.

High Level Language:

It is easier to write program in Higher Level Language (HLL) than Assembly Language. Moreover, a program written in HLL can be used on any computer irrespective of the type of microprocessor and HW in computer, provided it has a compiler for the HLL used for programming.

Advantages of HLL Programming are:

1. Easier to learn as compared to assembly languages.
2. Most of the instructions are as like simple English.
3. Better documentation is provided for HLL.
4. The executions do not depend on type of HW in computer.

Some of the popular HLL are BASIC, FORTRAN, COBOL, PASCAL, C, etc. Every HLL has a vocabulary of specific words (commands) and set of rules to use these words called syntax. The set of commands include instructions for various operations like arithmetic and logic operations on the data, input and output and control statements. However, computer needs special means to convert a program written in HLL to machine language. These translators are called interpreters or compilers.